[wpilibcintegrationtests] Fix deprecated Preferences usage (#3461)

This reverts commit d068fb321f (#3420).

The 18.04 docker images now use GCC 8, which was the original reason for
updating.  20.04 uses a much more recent libc, so staying with 18.04
enables more Linux platforms to use the binaries.

.clang-tidy

@@ -4,7 +4,6 @@ Checks:
   bugprone-copy-constructor-init,
   bugprone-dangling-handle,
   bugprone-dynamic-static-initializers,
-  bugprone-exception-escape,
   bugprone-forward-declaration-namespace,
   bugprone-forwarding-reference-overload,
   bugprone-inaccurate-erase,

.github/workflows/cmake.yml

@@ -10,7 +10,7 @@ jobs:
         include:
           - os: ubuntu-latest
             name: Linux
-            container: wpilib/roborio-cross-ubuntu:2020-18.04
+            container: wpilib/roborio-cross-ubuntu:2021-18.04
             flags: ""
           - os: macos-latest
             name: macOS

.github/workflows/documentation.yml

@@ -9,7 +9,7 @@ jobs:
   publish:
     name: "Documentation - Publish"
     runs-on: ubuntu-latest
-    if: github.repository_owner == 'wpilibsuite' && (github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/tags/v'))
+    if: github.repository_owner == 'wpilibsuite' && (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/v'))
     steps:
       - uses: actions/checkout@v2
         with:
@@ -21,7 +21,7 @@ jobs:
       - name: Set environment variables (Development)
         run: |
           echo "TARGET_FOLDER=$BASE_PATH/development" >> $GITHUB_ENV
-        if: github.ref == 'refs/heads/master'
+        if: github.ref == 'refs/heads/main'
       - name: Set environment variables (Tag)
         run: |
           echo "EXTRA_GRADLE_ARGS=-PreleaseMode" >> $GITHUB_ENV

.github/workflows/gradle-wrapper-validation.yml

@@ -1,5 +1,5 @@
 name: "Validate Gradle Wrapper"
-on: [push, pull_request]
+on: [pull_request, push]
 
 jobs:
   validation:

.github/workflows/gradle.yml

@@ -71,12 +71,12 @@ jobs:
           keychain-password: ${{ secrets.APPLE_KEYCHAIN_PASSWORD }}
         if: |
           matrix.artifact-name == 'macOS' && (github.repository_owner == 'wpilibsuite' &&
-          (github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/tags/v')))
+          (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/v')))
       - name: Set Keychain Lock Timeout
         run: security set-keychain-settings -lut 3600
         if: |
           matrix.artifact-name == 'macOS' && (github.repository_owner == 'wpilibsuite' &&
-          (github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/tags/v')))
+          (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/v')))
       - name: Set release environment variable
         run: echo "EXTRA_GRADLE_ARGS=-PreleaseMode" >> $GITHUB_ENV
         shell: bash
@@ -87,7 +87,7 @@ jobs:
         run: ./gradlew build -PbuildServer -PdeveloperID=${{ secrets.APPLE_DEVELOPER_ID }} ${{ env.EXTRA_GRADLE_ARGS }}
         if: |
           matrix.artifact-name == 'macOS' && (github.repository_owner == 'wpilibsuite' &&
-          (github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/tags/v')))
+          (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/v')))
       - uses: actions/upload-artifact@v2
         with:
           name: ${{ matrix.artifact-name }}
@@ -136,12 +136,12 @@ jobs:
       - name: Combine
         if: |
           !startsWith(github.ref, 'refs/tags/v') &&
-          github.ref != 'refs/heads/master'
+          github.ref != 'refs/heads/main'
         run: cd combiner && ./gradlew publish -Pallwpilib
       - name: Combine (Master)
         if: |
           github.repository_owner == 'wpilibsuite' &&
-          github.ref == 'refs/heads/master'
+          github.ref == 'refs/heads/main'
         run: cd combiner && ./gradlew publish -Pallwpilib
         env:
           RUN_AZURE_ARTIFACTORY_RELEASE: "TRUE"

.github/workflows/lint-format.yml

@@ -1,47 +1,58 @@
 name: Lint and Format
 
-on: [pull_request]
+on:
+  pull_request:
+  push:
+    branches-ignore:
+      - main
 
 jobs:
   wpiformat:
     name: "wpiformat"
     runs-on: ubuntu-latest
+    container: wpilib/roborio-cross-ubuntu:2021-20.04
     steps:
       - uses: actions/checkout@v2
       - name: Fetch all history and metadata
         run: |
           git fetch --prune --unshallow
           git checkout -b pr
-          git branch -f master origin/master
+          git branch -f main origin/main
       - name: Set up Python 3.8
         uses: actions/setup-python@v2
         with:
           python-version: 3.8
       - name: Install clang-format
-        run: sudo apt-get update -q && sudo apt-get install -y clang-format-10
+        run: |
+          sudo sh -c "echo 'deb http://archive.ubuntu.com/ubuntu/ $(lsb_release -cs)-proposed restricted main multiverse universe' >> /etc/apt/sources.list.d/proposed-repositories.list"
+          sudo apt-get update -q
+          sudo apt-get install -y clang-format-12
       - name: Install wpiformat
         run: pip3 install wpiformat
       - name: Run
-        run: wpiformat -clang 10
+        run: wpiformat -clang 12
       - name: Check Output
         run: git --no-pager diff --exit-code HEAD
   tidy:
     name: "clang-tidy"
     runs-on: ubuntu-latest
-    container: wpilib/roborio-cross-ubuntu:2020-18.04
+    container: wpilib/roborio-cross-ubuntu:2021-20.04
     steps:
       - uses: actions/checkout@v2
       - name: Fetch all history and metadata
         run: |
           git fetch --prune --unshallow
           git checkout -b pr
-          git branch -f master origin/master
+          git branch -f main origin/main
       - name: Set up Python 3.8
         uses: actions/setup-python@v2
         with:
           python-version: 3.8
-      - name: Install clang-format and clang-tidy
-        run: sudo apt-get update -q && sudo apt-get install -y clang-format-10 clang-tidy-10
+      - name: Install clang-tidy
+        run: |
+          sudo sh -c "echo 'deb http://archive.ubuntu.com/ubuntu/ $(lsb_release -cs)-proposed restricted main multiverse universe' >> /etc/apt/sources.list.d/proposed-repositories.list"
+          sudo apt-get update -q
+          sudo apt-get install -y clang-tidy-12 clang-format-12
       - name: Install wpiformat
         run: pip3 install wpiformat
       - name: Create compile_commands.json
@@ -49,4 +60,4 @@ jobs:
       - name: List changed files
         run: wpiformat -list-changed-files
       - name: Run clang-tidy
-        run: wpiformat -clang 10 -no-format -tidy-changed -compile-commands=build-cmake
+        run: wpiformat -clang 12 -no-format -tidy-changed -compile-commands=build-cmake

.gitignore

@@ -222,5 +222,6 @@ compile_commands.json
 # clang configuration and clangd cache
 .clang
 .clangd/
+.cache/
 
 imgui.ini

.styleguide

@@ -23,6 +23,7 @@ includeOtherLibs {
   ^cameraserver/
   ^cscore
   ^drake/
+  ^fmt/
   ^hal/
   ^imgui
   ^implot

CMakeLists.txt

@@ -59,6 +59,7 @@ option(WITH_EXTERNAL_HAL "Use a separately built HAL" OFF)
 set(EXTERNAL_HAL_FILE "" CACHE FILEPATH "Location to look for an external HAL CMake File")
 
 # Options for using a package manager (vcpkg) for certain dependencies.
+option(USE_VCPKG_FMTLIB "Use vcpkg fmtlib" OFF)
 option(USE_VCPKG_LIBUV "Use vcpkg libuv" OFF)
 option(USE_VCPKG_EIGEN "Use vcpkg eigen" OFF)
 
@@ -187,6 +188,12 @@ if (WITH_GUI)
     add_subdirectory(imgui)
     add_subdirectory(wpigui)
     add_subdirectory(glass)
+    add_subdirectory(outlineviewer)
+endif()
+
+if (WITH_WPILIB OR WITH_SIMULATION_MODULES)
+    set(HAL_DEP_REPLACE ${HAL_DEP_REPLACE_IMPL})
+    add_subdirectory(hal)
 endif()
 
 if (WITH_CSCORE)
@@ -195,9 +202,7 @@ if (WITH_CSCORE)
     add_subdirectory(cscore)
     add_subdirectory(cameraserver)
     if (WITH_WPILIB)
-        set(HAL_DEP_REPLACE ${HAL_DEP_REPLACE_IMPL})
         set(WPILIBC_DEP_REPLACE ${WPILIBC_DEP_REPLACE_IMPL})
-        add_subdirectory(hal)
         add_subdirectory(wpilibj)
         add_subdirectory(wpilibc)
         add_subdirectory(wpilibNewCommands)

CONTRIBUTING.md

@@ -1,6 +1,6 @@
 # Contributing to WPILib
 
-So you want to contribute your changes back to WPILib. Great! We have a few contributing rules that will help you make sure your changes will be accepted into the project. Please remember to follow the rules in the [code of conduct](https://github.com/wpilibsuite/allwpilib/blob/master/CODE_OF_CONDUCT.md), and behave with Gracious Professionalism.
+So you want to contribute your changes back to WPILib. Great! We have a few contributing rules that will help you make sure your changes will be accepted into the project. Please remember to follow the rules in the [code of conduct](https://github.com/wpilibsuite/allwpilib/blob/main/CODE_OF_CONDUCT.md), and behave with Gracious Professionalism.
 
 - [General Contribution Rules](#general-contribution-rules)
 - [What to Contribute](#what-to-contribute)
@@ -45,7 +45,7 @@ While the library should be fully formatted according to the styles, additional
 
 ### Pull Request Format
 
-Changes should be submitted as a Pull Request against the master branch of WPILib. For most changes, commits will be squashed upon merge. For particularly large changes, multiple commits are ok, but assume one commit unless asked otherwise. We may ask you to break a PR into multiple standalone PRs or commits for rebase within one PR to separate unrelated changes. No change will be merged unless it is up to date with the current master. We do this to make sure that the git history isn't too cluttered.
+Changes should be submitted as a Pull Request against the main branch of WPILib. For most changes, commits will be squashed upon merge. For particularly large changes, multiple commits are ok, but assume one commit unless asked otherwise. We may ask you to break a PR into multiple standalone PRs or commits for rebase within one PR to separate unrelated changes. No change will be merged unless it is up to date with the current main branch. We do this to make sure that the git history isn't too cluttered.
 
 ### Merge Process
 

MAINTAINERS.md

@@ -11,10 +11,10 @@ For Java dependencies, there is likely a file related to the specific dependency
 Note, changing artifact locations (This includes changing the artifact year currently, I have an issue open to change this) requires updating the `native-utils` plugin
 
 ## Publishing allwpilib
-allwpilib publishes to the development repo on every push to master. To publish a release build, upload a new tag, and a release will automatically be built and published.
+allwpilib publishes to the development repo on every push to main. To publish a release build, upload a new tag, and a release will automatically be built and published.
 
 ## Publishing desktop tools
-Desktop tools publish to the development repo on every push to master. To publish a release build, upload a new tag, and a release will automatically be built and published.
+Desktop tools publish to the development repo on every push to main. To publish a release build, upload a new tag, and a release will automatically be built and published.
 
 ## Publishing VS Code
 Before publishing, make sure to update the gradlerio version in `vscode-wpilib/resources/gradle/version.txt` Also make sure the gradle wrapper version matches the wrapper required by gradlerio.

MavenArtifacts.md

@@ -9,7 +9,7 @@ We provide two repositories. These repositories are:
 * (Development) https://frcmaven.wpi.edu/artifactory/development/
 
 The release repository is where official WPILib releases are pushed.
-The development repository is where development releases of every commit to [master](https://github.com/wpilibsuite/allwpilib/tree/master) is pushed.
+The development repository is where development releases of every commit to [main](https://github.com/wpilibsuite/allwpilib/tree/main) is pushed.
 
 ## Artifact classifiers
 We provide two base types of artifacts.

README.md

@@ -51,7 +51,7 @@ Using Gradle makes building WPILib very straightforward. It only has a few depen
 
 Clone the WPILib repository and follow the instructions above for installing any required tooling.
 
-See the [styleguide README](https://github.com/wpilibsuite/styleguide/blob/master/README.md) for wpiformat setup instructions.
+See the [styleguide README](https://github.com/wpilibsuite/styleguide/blob/main/README.md) for wpiformat setup instructions.
 
 ## Building
 

ThirdPartyNotices.txt

@@ -27,6 +27,7 @@ JSON for Modern C++   wpiutil/src/main/native/include/wpi/json.h
 libuv                 wpiutil/src/main/native/include/uv.h
                       wpiutil/src/main/native/include/uv/
                       wpiutil/src/main/native/libuv/
+fmtlib                wpiutil/src/main/native/fmtlib/
 sigslot               wpiutil/src/main/native/include/wpi/Signal.h
                       wpiutil/src/test/native/cpp/sigslot/
 tcpsockets            wpiutil/src/main/native/cpp/TCP{Stream,Connector,Acceptor}.cpp
@@ -40,6 +41,9 @@ units                 wpimath/src/main/native/include/units/
 Eigen                 wpimath/src/main/native/eigeninclude/
                       wpimath/src/main/native/include/unsupported/
 StackWalker           wpiutil/src/main/native/windows/StackWalker.*
+TCB span              wpiutil/src/main/native/include/wpi/span.h
+                      wpiutil/src/test/native/cpp/span/
+GHC filesystem        wpiutil/src/main/native/include/wpi/ghc/
 Team 254 Library      wpilibj/src/main/java/edu/wpi/first/wpilibj/spline/SplineParameterizer.java
                       wpilibj/src/main/java/edu/wpi/first/wpilibj/trajectory/TrajectoryParameterizer.java
                       wpilibc/src/main/native/include/spline/SplineParameterizer.h
@@ -856,3 +860,84 @@ the extent permitted by applicable law. You can redistribute it
 and/or modify it under the terms of the Do What the **** You Want
 to Public License, Version 2, as published by the WTFPL Task Force.
 See http://www.wtfpl.net/ for more details.
+
+======================
+Boost Software License
+======================
+Boost Software License - Version 1.0 - August 17th, 2003
+
+Permission is hereby granted, free of charge, to any person or organization
+obtaining a copy of the software and accompanying documentation covered by
+this license (the "Software") to use, reproduce, display, distribute,
+execute, and transmit the Software, and to prepare derivative works of the
+Software, and to permit third-parties to whom the Software is furnished to
+do so, all subject to the following:
+
+The copyright notices in the Software and this entire statement, including
+the above license grant, this restriction and the following disclaimer,
+must be included in all copies of the Software, in whole or in part, and
+all derivative works of the Software, unless such copies or derivative
+works are solely in the form of machine-executable object code generated by
+a source language processor.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
+======
+fmtlib
+======
+Copyright (c) 2012 - present, Victor Zverovich
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+--- Optional exception to the license ---
+
+As an exception, if, as a result of your compiling your source code, portions
+of this Software are embedded into a machine-executable object form of such
+source code, you may redistribute such embedded portions in such object form
+without including the above copyright and permission notices.
+
+==============
+GHC filesystem
+==============
+Copyright (c) 2018, Steffen Schümann <s.schuemann@pobox.com>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

buildSrc/build.gradle

@@ -5,5 +5,5 @@ repositories {
     }
 }
 dependencies {
-    implementation "edu.wpi.first:native-utils:2021.1.1"
+    implementation "edu.wpi.first:native-utils:2022.0.2"
 }

cameraserver/.styleguide

@@ -12,6 +12,7 @@ repoRootNameOverride {
 }
 
 includeOtherLibs {
+  ^fmt/
   ^hal/
   ^networktables/
   ^opencv2/

cameraserver/multiCameraServer/src/main/java/edu/wpi/Main.java

@@ -10,8 +10,8 @@ import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonParser;
-import edu.wpi.cscore.VideoSource;
 import edu.wpi.first.cameraserver.CameraServer;
+import edu.wpi.first.cscore.VideoSource;
 import edu.wpi.first.networktables.NetworkTableInstance;
 import java.io.IOException;
 import java.nio.file.Files;
@@ -94,7 +94,6 @@ public final class Main {
   }
 
   /** Read configuration file. */
-  @SuppressWarnings("PMD.CyclomaticComplexity")
   public static boolean readConfig() {
     // parse file
     JsonElement top;
@@ -151,7 +150,7 @@ public final class Main {
   /** Start running the camera. */
   public static void startCamera(CameraConfig config) {
     System.out.println("Starting camera '" + config.name + "' on " + config.path);
-    VideoSource camera = CameraServer.getInstance().startAutomaticCapture(config.name, config.path);
+    VideoSource camera = CameraServer.startAutomaticCapture(config.name, config.path);
 
     Gson gson = new GsonBuilder().create();
 

cameraserver/multiCameraServer/src/main/native/cpp/main.cpp

@@ -4,10 +4,12 @@
 
 #include <cstdio>
 #include <string>
+#include <string_view>
 #include <vector>
 
 #include <networktables/NetworkTableInstance.h>
-#include <wpi/StringRef.h>
+#include <wpi/StringExtras.h>
+#include <wpi/fmt/raw_ostream.h>
 #include <wpi/json.h>
 #include <wpi/raw_istream.h>
 #include <wpi/raw_ostream.h>
@@ -105,7 +107,7 @@ bool ReadConfig() {
   try {
     j = wpi::json::parse(is);
   } catch (const wpi::json::parse_error& e) {
-    ParseError() << "byte " << e.byte << ": " << e.what() << '\n';
+    fmt::print(ParseError(), "byte {}: {}\n", e.byte, e.what());
     return false;
   }
 
@@ -127,10 +129,9 @@ bool ReadConfig() {
   if (j.count("ntmode") != 0) {
     try {
       auto str = j.at("ntmode").get<std::string>();
-      wpi::StringRef s(str);
-      if (s.equals_lower("client")) {
+      if (wpi::equals_lower(str, "client")) {
         server = false;
-      } else if (s.equals_lower("server")) {
+      } else if (wpi::equals_lower(str, "server")) {
         server = true;
       } else {
         ParseError() << "could not understand ntmode value '" << str << "'\n";
@@ -156,10 +157,9 @@ bool ReadConfig() {
 }
 
 void StartCamera(const CameraConfig& config) {
-  wpi::outs() << "Starting camera '" << config.name << "' on " << config.path
-              << '\n';
-  auto camera = frc::CameraServer::GetInstance()->StartAutomaticCapture(
-      config.name, config.path);
+  fmt::print("Starting camera '{}' on {}\n", config.name, config.path);
+  auto camera =
+      frc::CameraServer::StartAutomaticCapture(config.name, config.path);
 
   camera.SetConfigJson(config.config);
 }
@@ -178,10 +178,10 @@ int main(int argc, char* argv[]) {
   // start NetworkTables
   auto ntinst = nt::NetworkTableInstance::GetDefault();
   if (server) {
-    wpi::outs() << "Setting up NetworkTables server\n";
+    std::puts("Setting up NetworkTables server");
     ntinst.StartServer();
   } else {
-    wpi::outs() << "Setting up NetworkTables client for team " << team << '\n';
+    fmt::print("Setting up NetworkTables client for team {}\n", team);
     ntinst.StartClientTeam(team);
   }
 

cameraserver/src/main/java/edu/wpi/first/cameraserver/CameraServer.java

@@ -4,20 +4,20 @@
 
 package edu.wpi.first.cameraserver;
 
-import edu.wpi.cscore.AxisCamera;
-import edu.wpi.cscore.CameraServerJNI;
-import edu.wpi.cscore.CvSink;
-import edu.wpi.cscore.CvSource;
-import edu.wpi.cscore.MjpegServer;
-import edu.wpi.cscore.UsbCamera;
-import edu.wpi.cscore.VideoEvent;
-import edu.wpi.cscore.VideoException;
-import edu.wpi.cscore.VideoListener;
-import edu.wpi.cscore.VideoMode;
-import edu.wpi.cscore.VideoMode.PixelFormat;
-import edu.wpi.cscore.VideoProperty;
-import edu.wpi.cscore.VideoSink;
-import edu.wpi.cscore.VideoSource;
+import edu.wpi.first.cscore.AxisCamera;
+import edu.wpi.first.cscore.CameraServerJNI;
+import edu.wpi.first.cscore.CvSink;
+import edu.wpi.first.cscore.CvSource;
+import edu.wpi.first.cscore.MjpegServer;
+import edu.wpi.first.cscore.UsbCamera;
+import edu.wpi.first.cscore.VideoEvent;
+import edu.wpi.first.cscore.VideoException;
+import edu.wpi.first.cscore.VideoListener;
+import edu.wpi.first.cscore.VideoMode;
+import edu.wpi.first.cscore.VideoMode.PixelFormat;
+import edu.wpi.first.cscore.VideoProperty;
+import edu.wpi.first.cscore.VideoSink;
+import edu.wpi.first.cscore.VideoSource;
 import edu.wpi.first.networktables.EntryListenerFlags;
 import edu.wpi.first.networktables.NetworkTable;
 import edu.wpi.first.networktables.NetworkTableEntry;
@@ -33,6 +33,7 @@ import java.util.concurrent.atomic.AtomicInteger;
  * Singleton class for creating and keeping camera servers. Also publishes camera information to
  * NetworkTables.
  */
+@SuppressWarnings("PMD.UnusedPrivateField")
 public final class CameraServer {
   public static final int kBasePort = 1181;
 
@@ -43,7 +44,12 @@ public final class CameraServer {
   private static final String kPublishName = "/CameraPublisher";
   private static CameraServer server;
 
-  /** Get the CameraServer instance. */
+  /**
+   * Get the CameraServer instance.
+   *
+   * @deprecated Use the static methods
+   */
+  @Deprecated
   public static synchronized CameraServer getInstance() {
     if (server == null) {
       server = new CameraServer();
@@ -51,18 +57,211 @@ public final class CameraServer {
     return server;
   }
 
-  private final AtomicInteger m_defaultUsbDevice;
-  private String m_primarySourceName;
-  private final Map<String, VideoSource> m_sources;
-  private final Map<String, VideoSink> m_sinks;
-  private final Map<Integer, NetworkTable> m_tables; // indexed by source handle
+  private static final AtomicInteger m_defaultUsbDevice = new AtomicInteger();
+  private static String m_primarySourceName;
+  private static final Map<String, VideoSource> m_sources = new HashMap<>();
+  private static final Map<String, VideoSink> m_sinks = new HashMap<>();
+  private static final Map<Integer, NetworkTable> m_tables =
+      new HashMap<>(); // indexed by source handle
   // source handle indexed by sink handle
-  private final Map<Integer, Integer> m_fixedSources;
-  private final NetworkTable m_publishTable;
-  private final VideoListener m_videoListener; // NOPMD
-  private final int m_tableListener; // NOPMD
-  private int m_nextPort;
-  private String[] m_addresses;
+  private static final Map<Integer, Integer> m_fixedSources = new HashMap<>();
+  private static final NetworkTable m_publishTable =
+      NetworkTableInstance.getDefault().getTable(kPublishName);
+
+  // We publish sources to NetworkTables using the following structure:
+  // "/CameraPublisher/{Source.Name}/" - root
+  // - "source" (string): Descriptive, prefixed with type (e.g. "usb:0")
+  // - "streams" (string array): URLs that can be used to stream data
+  // - "description" (string): Description of the source
+  // - "connected" (boolean): Whether source is connected
+  // - "mode" (string): Current video mode
+  // - "modes" (string array): Available video modes
+  // - "Property/{Property}" - Property values
+  // - "PropertyInfo/{Property}" - Property supporting information
+
+  // Listener for video events
+  private static final VideoListener m_videoListener =
+      new VideoListener(
+          event -> {
+            switch (event.kind) {
+              case kSourceCreated:
+                {
+                  // Create subtable for the camera
+                  NetworkTable table = m_publishTable.getSubTable(event.name);
+                  m_tables.put(event.sourceHandle, table);
+                  table.getEntry("source").setString(makeSourceValue(event.sourceHandle));
+                  table
+                      .getEntry("description")
+                      .setString(CameraServerJNI.getSourceDescription(event.sourceHandle));
+                  table
+                      .getEntry("connected")
+                      .setBoolean(CameraServerJNI.isSourceConnected(event.sourceHandle));
+                  table
+                      .getEntry("streams")
+                      .setStringArray(getSourceStreamValues(event.sourceHandle));
+                  try {
+                    VideoMode mode = CameraServerJNI.getSourceVideoMode(event.sourceHandle);
+                    table.getEntry("mode").setDefaultString(videoModeToString(mode));
+                    table.getEntry("modes").setStringArray(getSourceModeValues(event.sourceHandle));
+                  } catch (VideoException ignored) {
+                    // Do nothing. Let the other event handlers update this if there is an error.
+                  }
+                  break;
+                }
+              case kSourceDestroyed:
+                {
+                  NetworkTable table = m_tables.get(event.sourceHandle);
+                  if (table != null) {
+                    table.getEntry("source").setString("");
+                    table.getEntry("streams").setStringArray(new String[0]);
+                    table.getEntry("modes").setStringArray(new String[0]);
+                  }
+                  break;
+                }
+              case kSourceConnected:
+                {
+                  NetworkTable table = m_tables.get(event.sourceHandle);
+                  if (table != null) {
+                    // update the description too (as it may have changed)
+                    table
+                        .getEntry("description")
+                        .setString(CameraServerJNI.getSourceDescription(event.sourceHandle));
+                    table.getEntry("connected").setBoolean(true);
+                  }
+                  break;
+                }
+              case kSourceDisconnected:
+                {
+                  NetworkTable table = m_tables.get(event.sourceHandle);
+                  if (table != null) {
+                    table.getEntry("connected").setBoolean(false);
+                  }
+                  break;
+                }
+              case kSourceVideoModesUpdated:
+                {
+                  NetworkTable table = m_tables.get(event.sourceHandle);
+                  if (table != null) {
+                    table.getEntry("modes").setStringArray(getSourceModeValues(event.sourceHandle));
+                  }
+                  break;
+                }
+              case kSourceVideoModeChanged:
+                {
+                  NetworkTable table = m_tables.get(event.sourceHandle);
+                  if (table != null) {
+                    table.getEntry("mode").setString(videoModeToString(event.mode));
+                  }
+                  break;
+                }
+              case kSourcePropertyCreated:
+                {
+                  NetworkTable table = m_tables.get(event.sourceHandle);
+                  if (table != null) {
+                    putSourcePropertyValue(table, event, true);
+                  }
+                  break;
+                }
+              case kSourcePropertyValueUpdated:
+                {
+                  NetworkTable table = m_tables.get(event.sourceHandle);
+                  if (table != null) {
+                    putSourcePropertyValue(table, event, false);
+                  }
+                  break;
+                }
+              case kSourcePropertyChoicesUpdated:
+                {
+                  NetworkTable table = m_tables.get(event.sourceHandle);
+                  if (table != null) {
+                    try {
+                      String[] choices =
+                          CameraServerJNI.getEnumPropertyChoices(event.propertyHandle);
+                      table
+                          .getEntry("PropertyInfo/" + event.name + "/choices")
+                          .setStringArray(choices);
+                    } catch (VideoException ignored) {
+                      // ignore
+                    }
+                  }
+                  break;
+                }
+              case kSinkSourceChanged:
+              case kSinkCreated:
+              case kSinkDestroyed:
+              case kNetworkInterfacesChanged:
+                {
+                  m_addresses = CameraServerJNI.getNetworkInterfaces();
+                  updateStreamValues();
+                  break;
+                }
+              default:
+                break;
+            }
+          },
+          0x4fff,
+          true);
+
+  private static final int m_tableListener =
+      NetworkTableInstance.getDefault()
+          .addEntryListener(
+              kPublishName + "/",
+              event -> {
+                String relativeKey = event.name.substring(kPublishName.length() + 1);
+
+                // get source (sourceName/...)
+                int subKeyIndex = relativeKey.indexOf('/');
+                if (subKeyIndex == -1) {
+                  return;
+                }
+                String sourceName = relativeKey.substring(0, subKeyIndex);
+                VideoSource source = m_sources.get(sourceName);
+                if (source == null) {
+                  return;
+                }
+
+                // get subkey
+                relativeKey = relativeKey.substring(subKeyIndex + 1);
+
+                // handle standard names
+                String propName;
+                if ("mode".equals(relativeKey)) {
+                  // reset to current mode
+                  event.getEntry().setString(videoModeToString(source.getVideoMode()));
+                  return;
+                } else if (relativeKey.startsWith("Property/")) {
+                  propName = relativeKey.substring(9);
+                } else if (relativeKey.startsWith("RawProperty/")) {
+                  propName = relativeKey.substring(12);
+                } else {
+                  return; // ignore
+                }
+
+                // everything else is a property
+                VideoProperty property = source.getProperty(propName);
+                switch (property.getKind()) {
+                  case kNone:
+                    return;
+                  case kBoolean:
+                    // reset to current setting
+                    event.getEntry().setBoolean(property.get() != 0);
+                    return;
+                  case kInteger:
+                  case kEnum:
+                    // reset to current setting
+                    event.getEntry().setDouble(property.get());
+                    return;
+                  case kString:
+                    // reset to current setting
+                    event.getEntry().setString(property.getString());
+                    return;
+                  default:
+                    return;
+                }
+              },
+              EntryListenerFlags.kImmediate | EntryListenerFlags.kUpdate);
+  private static int m_nextPort = kBasePort;
+  private static String[] m_addresses = new String[0];
 
   @SuppressWarnings("MissingJavadocMethod")
   private static String makeSourceValue(int source) {
@@ -90,8 +289,8 @@ public final class CameraServer {
     return "mjpg:http://" + address + ":" + port + "/?action=stream";
   }
 
-  @SuppressWarnings({"MissingJavadocMethod", "PMD.AvoidUsingHardCodedIP"})
-  private synchronized String[] getSinkStreamValues(int sink) {
+  @SuppressWarnings("MissingJavadocMethod")
+  private static synchronized String[] getSinkStreamValues(int sink) {
     // Ignore all but MjpegServer
     if (VideoSink.getKindFromInt(CameraServerJNI.getSinkKind(sink)) != VideoSink.Kind.kMjpeg) {
       return new String[0];
@@ -120,8 +319,8 @@ public final class CameraServer {
     return values.toArray(new String[0]);
   }
 
-  @SuppressWarnings({"MissingJavadocMethod", "PMD.AvoidUsingHardCodedIP"})
-  private synchronized String[] getSourceStreamValues(int source) {
+  @SuppressWarnings("MissingJavadocMethod")
+  private static synchronized String[] getSourceStreamValues(int source) {
     // Ignore all but HttpCamera
     if (VideoSource.getKindFromInt(CameraServerJNI.getSourceKind(source))
         != VideoSource.Kind.kHttp) {
@@ -155,12 +354,8 @@ public final class CameraServer {
     return values;
   }
 
-  @SuppressWarnings({
-    "MissingJavadocMethod",
-    "PMD.AvoidUsingHardCodedIP",
-    "PMD.CyclomaticComplexity"
-  })
-  private synchronized void updateStreamValues() {
+  @SuppressWarnings("MissingJavadocMethod")
+  private static synchronized void updateStreamValues() {
     // Over all the sinks...
     for (VideoSink i : m_sinks.values()) {
       int sink = i.getHandle();
@@ -247,7 +442,7 @@ public final class CameraServer {
     return modeStrings;
   }
 
-  @SuppressWarnings({"MissingJavadocMethod", "PMD.CyclomaticComplexity"})
+  @SuppressWarnings("MissingJavadocMethod")
   private static void putSourcePropertyValue(NetworkTable table, VideoEvent event, boolean isNew) {
     String name;
     String infoName;
@@ -304,223 +499,7 @@ public final class CameraServer {
     }
   }
 
-  @SuppressWarnings({
-    "MissingJavadocMethod",
-    "PMD.UnusedLocalVariable",
-    "PMD.ExcessiveMethodLength",
-    "PMD.NPathComplexity"
-  })
-  private CameraServer() {
-    m_defaultUsbDevice = new AtomicInteger();
-    m_sources = new HashMap<>();
-    m_sinks = new HashMap<>();
-    m_fixedSources = new HashMap<>();
-    m_tables = new HashMap<>();
-    m_publishTable = NetworkTableInstance.getDefault().getTable(kPublishName);
-    m_nextPort = kBasePort;
-    m_addresses = new String[0];
-
-    // We publish sources to NetworkTables using the following structure:
-    // "/CameraPublisher/{Source.Name}/" - root
-    // - "source" (string): Descriptive, prefixed with type (e.g. "usb:0")
-    // - "streams" (string array): URLs that can be used to stream data
-    // - "description" (string): Description of the source
-    // - "connected" (boolean): Whether source is connected
-    // - "mode" (string): Current video mode
-    // - "modes" (string array): Available video modes
-    // - "Property/{Property}" - Property values
-    // - "PropertyInfo/{Property}" - Property supporting information
-
-    // Listener for video events
-    m_videoListener =
-        new VideoListener(
-            event -> {
-              switch (event.kind) {
-                case kSourceCreated:
-                  {
-                    // Create subtable for the camera
-                    NetworkTable table = m_publishTable.getSubTable(event.name);
-                    m_tables.put(event.sourceHandle, table);
-                    table.getEntry("source").setString(makeSourceValue(event.sourceHandle));
-                    table
-                        .getEntry("description")
-                        .setString(CameraServerJNI.getSourceDescription(event.sourceHandle));
-                    table
-                        .getEntry("connected")
-                        .setBoolean(CameraServerJNI.isSourceConnected(event.sourceHandle));
-                    table
-                        .getEntry("streams")
-                        .setStringArray(getSourceStreamValues(event.sourceHandle));
-                    try {
-                      VideoMode mode = CameraServerJNI.getSourceVideoMode(event.sourceHandle);
-                      table.getEntry("mode").setDefaultString(videoModeToString(mode));
-                      table
-                          .getEntry("modes")
-                          .setStringArray(getSourceModeValues(event.sourceHandle));
-                    } catch (VideoException ignored) {
-                      // Do nothing. Let the other event handlers update this if there is an error.
-                    }
-                    break;
-                  }
-                case kSourceDestroyed:
-                  {
-                    NetworkTable table = m_tables.get(event.sourceHandle);
-                    if (table != null) {
-                      table.getEntry("source").setString("");
-                      table.getEntry("streams").setStringArray(new String[0]);
-                      table.getEntry("modes").setStringArray(new String[0]);
-                    }
-                    break;
-                  }
-                case kSourceConnected:
-                  {
-                    NetworkTable table = m_tables.get(event.sourceHandle);
-                    if (table != null) {
-                      // update the description too (as it may have changed)
-                      table
-                          .getEntry("description")
-                          .setString(CameraServerJNI.getSourceDescription(event.sourceHandle));
-                      table.getEntry("connected").setBoolean(true);
-                    }
-                    break;
-                  }
-                case kSourceDisconnected:
-                  {
-                    NetworkTable table = m_tables.get(event.sourceHandle);
-                    if (table != null) {
-                      table.getEntry("connected").setBoolean(false);
-                    }
-                    break;
-                  }
-                case kSourceVideoModesUpdated:
-                  {
-                    NetworkTable table = m_tables.get(event.sourceHandle);
-                    if (table != null) {
-                      table
-                          .getEntry("modes")
-                          .setStringArray(getSourceModeValues(event.sourceHandle));
-                    }
-                    break;
-                  }
-                case kSourceVideoModeChanged:
-                  {
-                    NetworkTable table = m_tables.get(event.sourceHandle);
-                    if (table != null) {
-                      table.getEntry("mode").setString(videoModeToString(event.mode));
-                    }
-                    break;
-                  }
-                case kSourcePropertyCreated:
-                  {
-                    NetworkTable table = m_tables.get(event.sourceHandle);
-                    if (table != null) {
-                      putSourcePropertyValue(table, event, true);
-                    }
-                    break;
-                  }
-                case kSourcePropertyValueUpdated:
-                  {
-                    NetworkTable table = m_tables.get(event.sourceHandle);
-                    if (table != null) {
-                      putSourcePropertyValue(table, event, false);
-                    }
-                    break;
-                  }
-                case kSourcePropertyChoicesUpdated:
-                  {
-                    NetworkTable table = m_tables.get(event.sourceHandle);
-                    if (table != null) {
-                      try {
-                        String[] choices =
-                            CameraServerJNI.getEnumPropertyChoices(event.propertyHandle);
-                        table
-                            .getEntry("PropertyInfo/" + event.name + "/choices")
-                            .setStringArray(choices);
-                      } catch (VideoException ignored) {
-                        // ignore
-                      }
-                    }
-                    break;
-                  }
-                case kSinkSourceChanged:
-                case kSinkCreated:
-                case kSinkDestroyed:
-                case kNetworkInterfacesChanged:
-                  {
-                    m_addresses = CameraServerJNI.getNetworkInterfaces();
-                    updateStreamValues();
-                    break;
-                  }
-                default:
-                  break;
-              }
-            },
-            0x4fff,
-            true);
-
-    // Listener for NetworkTable events
-    // We don't currently support changing settings via NT due to
-    // synchronization issues, so just update to current setting if someone
-    // else tries to change it.
-    m_tableListener =
-        NetworkTableInstance.getDefault()
-            .addEntryListener(
-                kPublishName + "/",
-                event -> {
-                  String relativeKey = event.name.substring(kPublishName.length() + 1);
-
-                  // get source (sourceName/...)
-                  int subKeyIndex = relativeKey.indexOf('/');
-                  if (subKeyIndex == -1) {
-                    return;
-                  }
-                  String sourceName = relativeKey.substring(0, subKeyIndex);
-                  VideoSource source = m_sources.get(sourceName);
-                  if (source == null) {
-                    return;
-                  }
-
-                  // get subkey
-                  relativeKey = relativeKey.substring(subKeyIndex + 1);
-
-                  // handle standard names
-                  String propName;
-                  if ("mode".equals(relativeKey)) {
-                    // reset to current mode
-                    event.getEntry().setString(videoModeToString(source.getVideoMode()));
-                    return;
-                  } else if (relativeKey.startsWith("Property/")) {
-                    propName = relativeKey.substring(9);
-                  } else if (relativeKey.startsWith("RawProperty/")) {
-                    propName = relativeKey.substring(12);
-                  } else {
-                    return; // ignore
-                  }
-
-                  // everything else is a property
-                  VideoProperty property = source.getProperty(propName);
-                  switch (property.getKind()) {
-                    case kNone:
-                      return;
-                    case kBoolean:
-                      // reset to current setting
-                      event.getEntry().setBoolean(property.get() != 0);
-                      return;
-                    case kInteger:
-                    case kEnum:
-                      // reset to current setting
-                      event.getEntry().setDouble(property.get());
-                      return;
-                    case kString:
-                      // reset to current setting
-                      event.getEntry().setString(property.getString());
-                      return;
-                    default:
-                      return;
-                  }
-                },
-                EntryListenerFlags.kImmediate | EntryListenerFlags.kUpdate);
-  }
+  private CameraServer() {}
 
   /**
    * Start automatically capturing images to send to the dashboard.
@@ -531,8 +510,10 @@ public final class CameraServer {
    * <p>The first time this overload is called, it calls {@link #startAutomaticCapture(int)} with
    * device 0, creating a camera named "USB Camera 0". Subsequent calls increment the device number
    * (e.g. 1, 2, etc).
+   *
+   * @return The USB camera capturing images.
    */
-  public UsbCamera startAutomaticCapture() {
+  public static UsbCamera startAutomaticCapture() {
     UsbCamera camera = startAutomaticCapture(m_defaultUsbDevice.getAndIncrement());
     CameraServerSharedStore.getCameraServerShared().reportUsbCamera(camera.getHandle());
     return camera;
@@ -545,8 +526,9 @@ public final class CameraServer {
    * {dev}".
    *
    * @param dev The device number of the camera interface
+   * @return The USB camera capturing images.
    */
-  public UsbCamera startAutomaticCapture(int dev) {
+  public static UsbCamera startAutomaticCapture(int dev) {
     UsbCamera camera = new UsbCamera("USB Camera " + dev, dev);
     startAutomaticCapture(camera);
     CameraServerSharedStore.getCameraServerShared().reportUsbCamera(camera.getHandle());
@@ -558,8 +540,9 @@ public final class CameraServer {
    *
    * @param name The name to give the camera
    * @param dev The device number of the camera interface
+   * @return The USB camera capturing images.
    */
-  public UsbCamera startAutomaticCapture(String name, int dev) {
+  public static UsbCamera startAutomaticCapture(String name, int dev) {
     UsbCamera camera = new UsbCamera(name, dev);
     startAutomaticCapture(camera);
     CameraServerSharedStore.getCameraServerShared().reportUsbCamera(camera.getHandle());
@@ -571,8 +554,9 @@ public final class CameraServer {
    *
    * @param name The name to give the camera
    * @param path The device path (e.g. "/dev/video0") of the camera
+   * @return The USB camera capturing images.
    */
-  public UsbCamera startAutomaticCapture(String name, String path) {
+  public static UsbCamera startAutomaticCapture(String name, String path) {
     UsbCamera camera = new UsbCamera(name, path);
     startAutomaticCapture(camera);
     CameraServerSharedStore.getCameraServerShared().reportUsbCamera(camera.getHandle());
@@ -583,8 +567,9 @@ public final class CameraServer {
    * Start automatically capturing images to send to the dashboard from an existing camera.
    *
    * @param camera Camera
+   * @return The MJPEG server serving images from the given camera.
    */
-  public MjpegServer startAutomaticCapture(VideoSource camera) {
+  public static MjpegServer startAutomaticCapture(VideoSource camera) {
     addCamera(camera);
     MjpegServer server = addServer("serve_" + camera.getName());
     server.setSource(camera);
@@ -597,8 +582,9 @@ public final class CameraServer {
    * <p>This overload calls {@link #addAxisCamera(String, String)} with name "Axis Camera".
    *
    * @param host Camera host IP or DNS name (e.g. "10.x.y.11")
+   * @return The Axis camera capturing images.
    */
-  public AxisCamera addAxisCamera(String host) {
+  public static AxisCamera addAxisCamera(String host) {
     return addAxisCamera("Axis Camera", host);
   }
 
@@ -608,8 +594,9 @@ public final class CameraServer {
    * <p>This overload calls {@link #addAxisCamera(String, String[])} with name "Axis Camera".
    *
    * @param hosts Array of Camera host IPs/DNS names
+   * @return The Axis camera capturing images.
    */
-  public AxisCamera addAxisCamera(String[] hosts) {
+  public static AxisCamera addAxisCamera(String[] hosts) {
     return addAxisCamera("Axis Camera", hosts);
   }
 
@@ -618,8 +605,9 @@ public final class CameraServer {
    *
    * @param name The name to give the camera
    * @param host Camera host IP or DNS name (e.g. "10.x.y.11")
+   * @return The Axis camera capturing images.
    */
-  public AxisCamera addAxisCamera(String name, String host) {
+  public static AxisCamera addAxisCamera(String name, String host) {
     AxisCamera camera = new AxisCamera(name, host);
     // Create a passthrough MJPEG server for USB access
     startAutomaticCapture(camera);
@@ -632,8 +620,9 @@ public final class CameraServer {
    *
    * @param name The name to give the camera
    * @param hosts Array of Camera host IPs/DNS names
+   * @return The Axis camera capturing images.
    */
-  public AxisCamera addAxisCamera(String name, String[] hosts) {
+  public static AxisCamera addAxisCamera(String name, String[] hosts) {
     AxisCamera camera = new AxisCamera(name, hosts);
     // Create a passthrough MJPEG server for USB access
     startAutomaticCapture(camera);
@@ -645,12 +634,15 @@ public final class CameraServer {
    * Adds a virtual camera for switching between two streams. Unlike the other addCamera methods,
    * this returns a VideoSink rather than a VideoSource. Calling setSource() on the returned object
    * can be used to switch the actual source of the stream.
+   *
+   * @param name The name to give the camera
+   * @return The MJPEG server serving images from the given camera.
    */
-  public MjpegServer addSwitchedCamera(String name) {
+  public static MjpegServer addSwitchedCamera(String name) {
     // create a dummy CvSource
     CvSource source = new CvSource(name, VideoMode.PixelFormat.kMJPEG, 160, 120, 30);
     MjpegServer server = startAutomaticCapture(source);
-    synchronized (this) {
+    synchronized (CameraServer.class) {
       m_fixedSources.put(server.getHandle(), source.getHandle());
     }
 
@@ -663,10 +655,12 @@ public final class CameraServer {
    *
    * <p>This is only valid to call after a camera feed has been added with startAutomaticCapture()
    * or addServer().
+   *
+   * @return OpenCV sink for the primary camera feed
    */
-  public CvSink getVideo() {
+  public static CvSink getVideo() {
     VideoSource source;
-    synchronized (this) {
+    synchronized (CameraServer.class) {
       if (m_primarySourceName == null) {
         throw new VideoException("no camera available");
       }
@@ -683,11 +677,12 @@ public final class CameraServer {
    * image processing on the roboRIO.
    *
    * @param camera Camera (e.g. as returned by startAutomaticCapture).
+   * @return OpenCV sink for the specified camera
    */
-  public CvSink getVideo(VideoSource camera) {
+  public static CvSink getVideo(VideoSource camera) {
     String name = "opencv_" + camera.getName();
 
-    synchronized (this) {
+    synchronized (CameraServer.class) {
       VideoSink sink = m_sinks.get(name);
       if (sink != null) {
         VideoSink.Kind kind = sink.getKind();
@@ -709,10 +704,11 @@ public final class CameraServer {
    * image processing on the roboRIO.
    *
    * @param name Camera name
+   * @return OpenCV sink for the specified camera
    */
-  public CvSink getVideo(String name) {
+  public static CvSink getVideo(String name) {
     VideoSource source;
-    synchronized (this) {
+    synchronized (CameraServer.class) {
       source = m_sources.get(name);
       if (source == null) {
         throw new VideoException("could not find camera " + name);
@@ -728,8 +724,9 @@ public final class CameraServer {
    * @param name Name to give the stream
    * @param width Width of the image being sent
    * @param height Height of the image being sent
+   * @return OpenCV source for the MJPEG stream
    */
-  public CvSource putVideo(String name, int width, int height) {
+  public static CvSource putVideo(String name, int width, int height) {
     CvSource source = new CvSource(name, VideoMode.PixelFormat.kMJPEG, width, height, 30);
     startAutomaticCapture(source);
     return source;
@@ -739,10 +736,11 @@ public final class CameraServer {
    * Adds a MJPEG server at the next available port.
    *
    * @param name Server name
+   * @return The MJPEG server
    */
-  public MjpegServer addServer(String name) {
+  public static MjpegServer addServer(String name) {
     int port;
-    synchronized (this) {
+    synchronized (CameraServer.class) {
       port = m_nextPort;
       m_nextPort++;
     }
@@ -753,8 +751,10 @@ public final class CameraServer {
    * Adds a MJPEG server.
    *
    * @param name Server name
+   * @param port Server port
+   * @return The MJPEG server
    */
-  public MjpegServer addServer(String name, int port) {
+  public static MjpegServer addServer(String name, int port) {
     MjpegServer server = new MjpegServer(name, port);
     addServer(server);
     return server;
@@ -765,8 +765,8 @@ public final class CameraServer {
    *
    * @param server Server
    */
-  public void addServer(VideoSink server) {
-    synchronized (this) {
+  public static void addServer(VideoSink server) {
+    synchronized (CameraServer.class) {
       m_sinks.put(server.getName(), server);
     }
   }
@@ -776,8 +776,8 @@ public final class CameraServer {
    *
    * @param name Server name
    */
-  public void removeServer(String name) {
-    synchronized (this) {
+  public static void removeServer(String name) {
+    synchronized (CameraServer.class) {
       m_sinks.remove(name);
     }
   }
@@ -787,9 +787,11 @@ public final class CameraServer {
    *
    * <p>This is only valid to call after a camera feed has been added with startAutomaticCapture()
    * or addServer().
+   *
+   * @return The server for the primary camera feed
    */
-  public VideoSink getServer() {
-    synchronized (this) {
+  public static VideoSink getServer() {
+    synchronized (CameraServer.class) {
       if (m_primarySourceName == null) {
         throw new VideoException("no camera available");
       }
@@ -801,9 +803,10 @@ public final class CameraServer {
    * Gets a server by name.
    *
    * @param name Server name
+   * @return The server
    */
-  public VideoSink getServer(String name) {
-    synchronized (this) {
+  public static VideoSink getServer(String name) {
+    synchronized (CameraServer.class) {
       return m_sinks.get(name);
     }
   }
@@ -813,9 +816,9 @@ public final class CameraServer {
    *
    * @param camera Camera
    */
-  public void addCamera(VideoSource camera) {
+  public static void addCamera(VideoSource camera) {
     String name = camera.getName();
-    synchronized (this) {
+    synchronized (CameraServer.class) {
       if (m_primarySourceName == null) {
         m_primarySourceName = name;
       }
@@ -828,8 +831,8 @@ public final class CameraServer {
    *
    * @param name Camera name
    */
-  public void removeCamera(String name) {
-    synchronized (this) {
+  public static void removeCamera(String name) {
+    synchronized (CameraServer.class) {
       m_sources.remove(name);
     }
   }

cameraserver/src/main/java/edu/wpi/first/cameraserver/CameraServerSharedStore.java

@@ -9,7 +9,11 @@ public final class CameraServerSharedStore {
 
   private CameraServerSharedStore() {}
 
-  /** get the CameraServerShared object. */
+  /**
+   * Get the CameraServerShared object.
+   *
+   * @return The CameraServerSharedObject
+   */
   public static synchronized CameraServerShared getCameraServerShared() {
     if (cameraServerShared == null) {
       cameraServerShared =
@@ -36,7 +40,11 @@ public final class CameraServerSharedStore {
     return cameraServerShared;
   }
 
-  /** set the CameraServerShared object. */
+  /**
+   * Set the CameraServerShared object.
+   *
+   * @param shared The CameraServerShared object.
+   */
   public static synchronized void setCameraServerShared(CameraServerShared shared) {
     cameraServerShared = shared;
   }

cameraserver/src/main/java/edu/wpi/first/vision/VisionPipeline.java

@@ -17,6 +17,8 @@ public interface VisionPipeline {
   /**
    * Processes the image input and sets the result objects. Implementations should make these
    * objects accessible.
+   *
+   * @param image The image to process.
    */
   void process(Mat image);
 }

cameraserver/src/main/java/edu/wpi/first/vision/VisionRunner.java

@@ -4,9 +4,9 @@
 
 package edu.wpi.first.vision;
 
-import edu.wpi.cscore.CvSink;
-import edu.wpi.cscore.VideoSource;
 import edu.wpi.first.cameraserver.CameraServerSharedStore;
+import edu.wpi.first.cscore.CvSink;
+import edu.wpi.first.cscore.VideoSource;
 import org.opencv.core.Mat;
 
 /**

cameraserver/src/main/java/edu/wpi/first/vision/VisionThread.java

@@ -4,7 +4,7 @@
 
 package edu.wpi.first.vision;
 
-import edu.wpi.cscore.VideoSource;
+import edu.wpi.first.cscore.VideoSource;
 
 /**
  * A vision thread is a special thread that runs a vision pipeline. It is a <i>daemon</i> thread; it

cameraserver/src/main/java/edu/wpi/first/vision/package-info.java

@@ -13,7 +13,7 @@
  *     implements VisionRunner.Listener<MyFindTotePipeline> {
  *
  *      // A USB camera connected to the roboRIO.
- *      private {@link edu.wpi.cscore.VideoSource VideoSource} usbCamera;
+ *      private {@link edu.wpi.first.cscore.VideoSource VideoSource} usbCamera;
  *
  *      // A vision pipeline. This could be handwritten or generated by GRIP.
  *      // This has to implement {@link edu.wpi.first.vision.VisionPipeline}.
@@ -44,7 +44,7 @@
  *
  *     {@literal @}Override
  *      public void robotInit() {
- *          usbCamera = CameraServer.getInstance().startAutomaticCapture(0);
+ *          usbCamera = CameraServer.startAutomaticCapture(0);
  *          findTotePipeline = new MyFindTotePipeline();
  *          findToteThread = new VisionThread(usbCamera, findTotePipeline, this);
  *      }

cameraserver/src/main/native/cpp/cameraserver/CameraServer.cpp

@@ -7,14 +7,14 @@
 #include <atomic>
 #include <vector>
 
+#include <fmt/format.h>
 #include <networktables/NetworkTable.h>
 #include <networktables/NetworkTableInstance.h>
 #include <wpi/DenseMap.h>
-#include <wpi/ManagedStatic.h>
 #include <wpi/SmallString.h>
+#include <wpi/StringExtras.h>
 #include <wpi/StringMap.h>
 #include <wpi/mutex.h>
-#include <wpi/raw_ostream.h>
 
 #include "cameraserver/CameraServerShared.h"
 #include "ntcore_cpp.h"
@@ -23,8 +23,9 @@ using namespace frc;
 
 static constexpr char const* kPublishName = "/CameraPublisher";
 
-struct CameraServer::Impl {
-  Impl();
+namespace {
+struct Instance {
+  Instance();
   std::shared_ptr<nt::NetworkTable> GetSourceTable(CS_Source source);
   std::vector<std::string> GetSinkStreamValues(CS_Sink sink);
   std::vector<std::string> GetSourceStreamValues(CS_Source source);
@@ -41,35 +42,36 @@ struct CameraServer::Impl {
       nt::NetworkTableInstance::GetDefault().GetTable(kPublishName)};
   cs::VideoListener m_videoListener;
   int m_tableListener;
-  int m_nextPort;
+  int m_nextPort{CameraServer::kBasePort};
   std::vector<std::string> m_addresses;
 };
+}  // namespace
 
-CameraServer* CameraServer::GetInstance() {
-  struct Creator {
-    static void* call() { return new CameraServer{}; }
-  };
-  struct Deleter {
-    static void call(void* ptr) { delete static_cast<CameraServer*>(ptr); }
-  };
-  static wpi::ManagedStatic<CameraServer, Creator, Deleter> instance;
-  return &(*instance);
+static Instance& GetInstance() {
+  static Instance instance;
+  return instance;
 }
 
-static wpi::StringRef MakeSourceValue(CS_Source source,
-                                      wpi::SmallVectorImpl<char>& buf) {
+CameraServer* CameraServer::GetInstance() {
+  ::GetInstance();
+  static CameraServer instance;
+  return &instance;
+}
+
+static std::string_view MakeSourceValue(CS_Source source,
+                                        wpi::SmallVectorImpl<char>& buf) {
   CS_Status status = 0;
   buf.clear();
   switch (cs::GetSourceKind(source, &status)) {
     case CS_SOURCE_USB: {
-      wpi::StringRef prefix{"usb:"};
+      std::string_view prefix{"usb:"};
       buf.append(prefix.begin(), prefix.end());
       auto path = cs::GetUsbCameraPath(source, &status);
       buf.append(path.begin(), path.end());
       break;
     }
     case CS_SOURCE_HTTP: {
-      wpi::StringRef prefix{"ip:"};
+      std::string_view prefix{"ip:"};
       buf.append(prefix.begin(), prefix.end());
       auto urls = cs::GetHttpCameraUrls(source, &status);
       if (!urls.empty()) {
@@ -83,22 +85,19 @@ static wpi::StringRef MakeSourceValue(CS_Source source,
       return "unknown:";
   }
 
-  return wpi::StringRef{buf.begin(), buf.size()};
+  return {buf.begin(), buf.size()};
 }
 
-static std::string MakeStreamValue(const wpi::Twine& address, int port) {
-  return ("mjpg:http://" + address + wpi::Twine(':') + wpi::Twine(port) +
-          "/?action=stream")
-      .str();
+static std::string MakeStreamValue(std::string_view address, int port) {
+  return fmt::format("mjpg:http://{}:{}/?action=stream", address, port);
 }
 
-std::shared_ptr<nt::NetworkTable> CameraServer::Impl::GetSourceTable(
-    CS_Source source) {
+std::shared_ptr<nt::NetworkTable> Instance::GetSourceTable(CS_Source source) {
   std::scoped_lock lock(m_mutex);
   return m_tables.lookup(source);
 }
 
-std::vector<std::string> CameraServer::Impl::GetSinkStreamValues(CS_Sink sink) {
+std::vector<std::string> Instance::GetSinkStreamValues(CS_Sink sink) {
   CS_Status status = 0;
 
   // Ignore all but MjpegServer
@@ -130,8 +129,7 @@ std::vector<std::string> CameraServer::Impl::GetSinkStreamValues(CS_Sink sink) {
   return values;
 }
 
-std::vector<std::string> CameraServer::Impl::GetSourceStreamValues(
-    CS_Source source) {
+std::vector<std::string> Instance::GetSourceStreamValues(CS_Source source) {
   CS_Status status = 0;
 
   // Ignore all but HttpCamera
@@ -165,7 +163,7 @@ std::vector<std::string> CameraServer::Impl::GetSourceStreamValues(
   return values;
 }
 
-void CameraServer::Impl::UpdateStreamValues() {
+void Instance::UpdateStreamValues() {
   std::scoped_lock lock(m_mutex);
   // Over all the sinks...
   for (const auto& i : m_sinks) {
@@ -229,12 +227,8 @@ static std::string PixelFormatToString(int pixelFormat) {
 }
 
 static std::string VideoModeToString(const cs::VideoMode& mode) {
-  std::string rv;
-  wpi::raw_string_ostream oss{rv};
-  oss << mode.width << "x" << mode.height;
-  oss << " " << PixelFormatToString(mode.pixelFormat) << " ";
-  oss << mode.fps << " fps";
-  return oss.str();
+  return fmt::format("{}x{} {} {} fps", mode.width, mode.height,
+                     PixelFormatToString(mode.pixelFormat), mode.fps);
 }
 
 static std::vector<std::string> GetSourceModeValues(int source) {
@@ -248,23 +242,20 @@ static std::vector<std::string> GetSourceModeValues(int source) {
 
 static void PutSourcePropertyValue(nt::NetworkTable* table,
                                    const cs::VideoEvent& event, bool isNew) {
-  wpi::SmallString<64> name;
-  wpi::SmallString<64> infoName;
-  if (wpi::StringRef{event.name}.startswith("raw_")) {
-    name = "RawProperty/";
-    name += event.name;
-    infoName = "RawPropertyInfo/";
-    infoName += event.name;
+  std::string_view namePrefix;
+  std::string_view infoPrefix;
+  if (wpi::starts_with(event.name, "raw_")) {
+    namePrefix = "RawProperty";
+    infoPrefix = "RawPropertyInfo";
   } else {
-    name = "Property/";
-    name += event.name;
-    infoName = "PropertyInfo/";
-    infoName += event.name;
+    namePrefix = "Property";
+    infoPrefix = "PropertyInfo";
   }
 
   wpi::SmallString<64> buf;
   CS_Status status = 0;
-  nt::NetworkTableEntry entry = table->GetEntry(name);
+  nt::NetworkTableEntry entry =
+      table->GetEntry(fmt::format("{}/{}", namePrefix, event.name));
   switch (event.propertyKind) {
     case CS_PROP_BOOLEAN:
       if (isNew) {
@@ -277,13 +268,13 @@ static void PutSourcePropertyValue(nt::NetworkTable* table,
     case CS_PROP_ENUM:
       if (isNew) {
         entry.SetDefaultDouble(event.value);
-        table->GetEntry(infoName + "/min")
+        table->GetEntry(fmt::format("{}/{}/min", infoPrefix, event.name))
             .SetDouble(cs::GetPropertyMin(event.propertyHandle, &status));
-        table->GetEntry(infoName + "/max")
+        table->GetEntry(fmt::format("{}/{}/max", infoPrefix, event.name))
             .SetDouble(cs::GetPropertyMax(event.propertyHandle, &status));
-        table->GetEntry(infoName + "/step")
+        table->GetEntry(fmt::format("{}/{}/step", infoPrefix, event.name))
             .SetDouble(cs::GetPropertyStep(event.propertyHandle, &status));
-        table->GetEntry(infoName + "/default")
+        table->GetEntry(fmt::format("{}/{}/default", infoPrefix, event.name))
             .SetDouble(cs::GetPropertyDefault(event.propertyHandle, &status));
       } else {
         entry.SetDouble(event.value);
@@ -301,7 +292,7 @@ static void PutSourcePropertyValue(nt::NetworkTable* table,
   }
 }
 
-CameraServer::Impl::Impl() : m_nextPort(kBasePort) {
+Instance::Instance() {
   // We publish sources to NetworkTables using the following structure:
   // "/CameraPublisher/{Source.Name}/" - root
   // - "source" (string): Descriptive, prefixed with type (e.g. "usb:0")
@@ -404,12 +395,11 @@ CameraServer::Impl::Impl() : m_nextPort(kBasePort) {
           case cs::VideoEvent::kSourcePropertyChoicesUpdated: {
             auto table = GetSourceTable(event.sourceHandle);
             if (table) {
-              wpi::SmallString<64> name{"PropertyInfo/"};
-              name += event.name;
-              name += "/choices";
               auto choices =
                   cs::GetEnumPropertyChoices(event.propertyHandle, &status);
-              table->GetEntry(name).SetStringArray(choices);
+              table
+                  ->GetEntry(fmt::format("PropertyInfo/{}/choices", event.name))
+                  .SetStringArray(choices);
             }
             break;
           }
@@ -433,35 +423,35 @@ CameraServer::Impl::Impl() : m_nextPort(kBasePort) {
   // else tries to change it.
   wpi::SmallString<64> buf;
   m_tableListener = nt::NetworkTableInstance::GetDefault().AddEntryListener(
-      kPublishName + wpi::Twine('/'),
+      fmt::format("{}/", kPublishName),
       [=](const nt::EntryNotification& event) {
-        wpi::StringRef relativeKey =
-            event.name.substr(wpi::StringRef(kPublishName).size() + 1);
+        auto relativeKey = wpi::drop_front(
+            event.name, std::string_view{kPublishName}.size() + 1);
 
         // get source (sourceName/...)
         auto subKeyIndex = relativeKey.find('/');
-        if (subKeyIndex == wpi::StringRef::npos) {
+        if (subKeyIndex == std::string_view::npos) {
           return;
         }
-        wpi::StringRef sourceName = relativeKey.slice(0, subKeyIndex);
+        auto sourceName = wpi::slice(relativeKey, 0, subKeyIndex);
         auto sourceIt = m_sources.find(sourceName);
         if (sourceIt == m_sources.end()) {
           return;
         }
 
         // get subkey
-        relativeKey = relativeKey.substr(subKeyIndex + 1);
+        relativeKey.remove_prefix(subKeyIndex + 1);
 
         // handle standard names
-        wpi::StringRef propName;
+        std::string_view propName;
         nt::NetworkTableEntry entry{event.entry};
         if (relativeKey == "mode") {
           // reset to current mode
           entry.SetString(VideoModeToString(sourceIt->second.GetVideoMode()));
           return;
-        } else if (relativeKey.startswith("Property/")) {
+        } else if (wpi::starts_with(relativeKey, "Property/")) {
           propName = relativeKey.substr(9);
-        } else if (relativeKey.startswith("RawProperty/")) {
+        } else if (wpi::starts_with(relativeKey, "RawProperty/")) {
           propName = relativeKey.substr(12);
         } else {
           return;  // ignore
@@ -489,26 +479,23 @@ CameraServer::Impl::Impl() : m_nextPort(kBasePort) {
       NT_NOTIFY_IMMEDIATE | NT_NOTIFY_UPDATE);
 }
 
-CameraServer::CameraServer() : m_impl(new Impl) {}
-
-CameraServer::~CameraServer() = default;
-
 cs::UsbCamera CameraServer::StartAutomaticCapture() {
-  cs::UsbCamera camera = StartAutomaticCapture(m_impl->m_defaultUsbDevice++);
+  cs::UsbCamera camera =
+      StartAutomaticCapture(::GetInstance().m_defaultUsbDevice++);
   auto csShared = GetCameraServerShared();
   csShared->ReportUsbCamera(camera.GetHandle());
   return camera;
 }
 
 cs::UsbCamera CameraServer::StartAutomaticCapture(int dev) {
-  cs::UsbCamera camera{"USB Camera " + wpi::Twine(dev), dev};
+  cs::UsbCamera camera{fmt::format("USB Camera {}", dev), dev};
   StartAutomaticCapture(camera);
   auto csShared = GetCameraServerShared();
   csShared->ReportUsbCamera(camera.GetHandle());
   return camera;
 }
 
-cs::UsbCamera CameraServer::StartAutomaticCapture(const wpi::Twine& name,
+cs::UsbCamera CameraServer::StartAutomaticCapture(std::string_view name,
                                                   int dev) {
   cs::UsbCamera camera{name, dev};
   StartAutomaticCapture(camera);
@@ -517,8 +504,8 @@ cs::UsbCamera CameraServer::StartAutomaticCapture(const wpi::Twine& name,
   return camera;
 }
 
-cs::UsbCamera CameraServer::StartAutomaticCapture(const wpi::Twine& name,
-                                                  const wpi::Twine& path) {
+cs::UsbCamera CameraServer::StartAutomaticCapture(std::string_view name,
+                                                  std::string_view path) {
   cs::UsbCamera camera{name, path};
   StartAutomaticCapture(camera);
   auto csShared = GetCameraServerShared();
@@ -526,7 +513,7 @@ cs::UsbCamera CameraServer::StartAutomaticCapture(const wpi::Twine& name,
   return camera;
 }
 
-cs::AxisCamera CameraServer::AddAxisCamera(const wpi::Twine& host) {
+cs::AxisCamera CameraServer::AddAxisCamera(std::string_view host) {
   return AddAxisCamera("Axis Camera", host);
 }
 
@@ -538,12 +525,12 @@ cs::AxisCamera CameraServer::AddAxisCamera(const std::string& host) {
   return AddAxisCamera("Axis Camera", host);
 }
 
-cs::AxisCamera CameraServer::AddAxisCamera(wpi::ArrayRef<std::string> hosts) {
+cs::AxisCamera CameraServer::AddAxisCamera(wpi::span<const std::string> hosts) {
   return AddAxisCamera("Axis Camera", hosts);
 }
 
-cs::AxisCamera CameraServer::AddAxisCamera(const wpi::Twine& name,
-                                           const wpi::Twine& host) {
+cs::AxisCamera CameraServer::AddAxisCamera(std::string_view name,
+                                           std::string_view host) {
   cs::AxisCamera camera{name, host};
   StartAutomaticCapture(camera);
   auto csShared = GetCameraServerShared();
@@ -551,7 +538,7 @@ cs::AxisCamera CameraServer::AddAxisCamera(const wpi::Twine& name,
   return camera;
 }
 
-cs::AxisCamera CameraServer::AddAxisCamera(const wpi::Twine& name,
+cs::AxisCamera CameraServer::AddAxisCamera(std::string_view name,
                                            const char* host) {
   cs::AxisCamera camera{name, host};
   StartAutomaticCapture(camera);
@@ -560,7 +547,7 @@ cs::AxisCamera CameraServer::AddAxisCamera(const wpi::Twine& name,
   return camera;
 }
 
-cs::AxisCamera CameraServer::AddAxisCamera(const wpi::Twine& name,
+cs::AxisCamera CameraServer::AddAxisCamera(std::string_view name,
                                            const std::string& host) {
   cs::AxisCamera camera{name, host};
   StartAutomaticCapture(camera);
@@ -569,8 +556,8 @@ cs::AxisCamera CameraServer::AddAxisCamera(const wpi::Twine& name,
   return camera;
 }
 
-cs::AxisCamera CameraServer::AddAxisCamera(const wpi::Twine& name,
-                                           wpi::ArrayRef<std::string> hosts) {
+cs::AxisCamera CameraServer::AddAxisCamera(std::string_view name,
+                                           wpi::span<const std::string> hosts) {
   cs::AxisCamera camera{name, hosts};
   StartAutomaticCapture(camera);
   auto csShared = GetCameraServerShared();
@@ -578,11 +565,11 @@ cs::AxisCamera CameraServer::AddAxisCamera(const wpi::Twine& name,
   return camera;
 }
 
-cs::MjpegServer CameraServer::AddSwitchedCamera(const wpi::Twine& name) {
+cs::MjpegServer CameraServer::AddSwitchedCamera(std::string_view name) {
   // create a dummy CvSource
   cs::CvSource source{name, cs::VideoMode::PixelFormat::kMJPEG, 160, 120, 30};
   cs::MjpegServer server = StartAutomaticCapture(source);
-  m_impl->m_fixedSources[server.GetHandle()] = source.GetHandle();
+  ::GetInstance().m_fixedSources[server.GetHandle()] = source.GetHandle();
 
   return server;
 }
@@ -590,22 +577,23 @@ cs::MjpegServer CameraServer::AddSwitchedCamera(const wpi::Twine& name) {
 cs::MjpegServer CameraServer::StartAutomaticCapture(
     const cs::VideoSource& camera) {
   AddCamera(camera);
-  auto server = AddServer(wpi::Twine("serve_") + camera.GetName());
+  auto server = AddServer(fmt::format("serve_{}", camera.GetName()));
   server.SetSource(camera);
   return server;
 }
 
 cs::CvSink CameraServer::GetVideo() {
+  auto& inst = ::GetInstance();
   cs::VideoSource source;
   {
     auto csShared = GetCameraServerShared();
-    std::scoped_lock lock(m_impl->m_mutex);
-    if (m_impl->m_primarySourceName.empty()) {
+    std::scoped_lock lock(inst.m_mutex);
+    if (inst.m_primarySourceName.empty()) {
       csShared->SetCameraServerError("no camera available");
       return cs::CvSink{};
     }
-    auto it = m_impl->m_sources.find(m_impl->m_primarySourceName);
-    if (it == m_impl->m_sources.end()) {
+    auto it = inst.m_sources.find(inst.m_primarySourceName);
+    if (it == inst.m_sources.end()) {
       csShared->SetCameraServerError("no camera available");
       return cs::CvSink{};
     }
@@ -615,40 +603,40 @@ cs::CvSink CameraServer::GetVideo() {
 }
 
 cs::CvSink CameraServer::GetVideo(const cs::VideoSource& camera) {
+  auto& inst = ::GetInstance();
   wpi::SmallString<64> name{"opencv_"};
   name += camera.GetName();
 
   {
-    std::scoped_lock lock(m_impl->m_mutex);
-    auto it = m_impl->m_sinks.find(name);
-    if (it != m_impl->m_sinks.end()) {
+    std::scoped_lock lock(inst.m_mutex);
+    auto it = inst.m_sinks.find(name);
+    if (it != inst.m_sinks.end()) {
       auto kind = it->second.GetKind();
       if (kind != cs::VideoSink::kCv) {
         auto csShared = GetCameraServerShared();
-        csShared->SetCameraServerError("expected OpenCV sink, but got " +
-                                       wpi::Twine(kind));
+        csShared->SetCameraServerError("expected OpenCV sink, but got {}",
+                                       kind);
         return cs::CvSink{};
       }
       return *static_cast<cs::CvSink*>(&it->second);
     }
   }
 
-  cs::CvSink newsink{name};
+  cs::CvSink newsink{name.str()};
   newsink.SetSource(camera);
   AddServer(newsink);
   return newsink;
 }
 
-cs::CvSink CameraServer::GetVideo(const wpi::Twine& name) {
-  wpi::SmallString<64> nameBuf;
-  wpi::StringRef nameStr = name.toStringRef(nameBuf);
+cs::CvSink CameraServer::GetVideo(std::string_view name) {
+  auto& inst = ::GetInstance();
   cs::VideoSource source;
   {
-    std::scoped_lock lock(m_impl->m_mutex);
-    auto it = m_impl->m_sources.find(nameStr);
-    if (it == m_impl->m_sources.end()) {
+    std::scoped_lock lock(inst.m_mutex);
+    auto it = inst.m_sources.find(name);
+    if (it == inst.m_sources.end()) {
       auto csShared = GetCameraServerShared();
-      csShared->SetCameraServerError("could not find camera " + nameStr);
+      csShared->SetCameraServerError("could not find camera {}", name);
       return cs::CvSink{};
     }
     source = it->second;
@@ -656,89 +644,92 @@ cs::CvSink CameraServer::GetVideo(const wpi::Twine& name) {
   return GetVideo(source);
 }
 
-cs::CvSource CameraServer::PutVideo(const wpi::Twine& name, int width,
+cs::CvSource CameraServer::PutVideo(std::string_view name, int width,
                                     int height) {
   cs::CvSource source{name, cs::VideoMode::kMJPEG, width, height, 30};
   StartAutomaticCapture(source);
   return source;
 }
 
-cs::MjpegServer CameraServer::AddServer(const wpi::Twine& name) {
+cs::MjpegServer CameraServer::AddServer(std::string_view name) {
+  auto& inst = ::GetInstance();
   int port;
   {
-    std::scoped_lock lock(m_impl->m_mutex);
-    port = m_impl->m_nextPort++;
+    std::scoped_lock lock(inst.m_mutex);
+    port = inst.m_nextPort++;
   }
   return AddServer(name, port);
 }
 
-cs::MjpegServer CameraServer::AddServer(const wpi::Twine& name, int port) {
+cs::MjpegServer CameraServer::AddServer(std::string_view name, int port) {
   cs::MjpegServer server{name, port};
   AddServer(server);
   return server;
 }
 
 void CameraServer::AddServer(const cs::VideoSink& server) {
-  std::scoped_lock lock(m_impl->m_mutex);
-  m_impl->m_sinks.try_emplace(server.GetName(), server);
+  auto& inst = ::GetInstance();
+  std::scoped_lock lock(inst.m_mutex);
+  inst.m_sinks.try_emplace(server.GetName(), server);
 }
 
-void CameraServer::RemoveServer(const wpi::Twine& name) {
-  std::scoped_lock lock(m_impl->m_mutex);
-  wpi::SmallString<64> nameBuf;
-  m_impl->m_sinks.erase(name.toStringRef(nameBuf));
+void CameraServer::RemoveServer(std::string_view name) {
+  auto& inst = ::GetInstance();
+  std::scoped_lock lock(inst.m_mutex);
+  inst.m_sinks.erase(name);
 }
 
 cs::VideoSink CameraServer::GetServer() {
-  wpi::SmallString<64> name;
+  auto& inst = ::GetInstance();
+  std::string name;
   {
-    std::scoped_lock lock(m_impl->m_mutex);
-    if (m_impl->m_primarySourceName.empty()) {
+    std::scoped_lock lock(inst.m_mutex);
+    if (inst.m_primarySourceName.empty()) {
       auto csShared = GetCameraServerShared();
       csShared->SetCameraServerError("no camera available");
       return cs::VideoSink{};
     }
-    name = "serve_";
-    name += m_impl->m_primarySourceName;
+    name = fmt::format("serve_{}", inst.m_primarySourceName);
   }
   return GetServer(name);
 }
 
-cs::VideoSink CameraServer::GetServer(const wpi::Twine& name) {
-  wpi::SmallString<64> nameBuf;
-  wpi::StringRef nameStr = name.toStringRef(nameBuf);
-  std::scoped_lock lock(m_impl->m_mutex);
-  auto it = m_impl->m_sinks.find(nameStr);
-  if (it == m_impl->m_sinks.end()) {
+cs::VideoSink CameraServer::GetServer(std::string_view name) {
+  auto& inst = ::GetInstance();
+  std::scoped_lock lock(inst.m_mutex);
+  auto it = inst.m_sinks.find(name);
+  if (it == inst.m_sinks.end()) {
     auto csShared = GetCameraServerShared();
-    csShared->SetCameraServerError("could not find server " + nameStr);
+    csShared->SetCameraServerError("could not find server {}", name);
     return cs::VideoSink{};
   }
   return it->second;
 }
 
 void CameraServer::AddCamera(const cs::VideoSource& camera) {
+  auto& inst = ::GetInstance();
   std::string name = camera.GetName();
-  std::scoped_lock lock(m_impl->m_mutex);
-  if (m_impl->m_primarySourceName.empty()) {
-    m_impl->m_primarySourceName = name;
+  std::scoped_lock lock(inst.m_mutex);
+  if (inst.m_primarySourceName.empty()) {
+    inst.m_primarySourceName = name;
   }
-  m_impl->m_sources.try_emplace(name, camera);
+  inst.m_sources.try_emplace(name, camera);
 }
 
-void CameraServer::RemoveCamera(const wpi::Twine& name) {
-  std::scoped_lock lock(m_impl->m_mutex);
-  wpi::SmallString<64> nameBuf;
-  m_impl->m_sources.erase(name.toStringRef(nameBuf));
+void CameraServer::RemoveCamera(std::string_view name) {
+  auto& inst = ::GetInstance();
+  std::scoped_lock lock(inst.m_mutex);
+  inst.m_sources.erase(name);
 }
 
 void CameraServer::SetSize(int size) {
-  std::scoped_lock lock(m_impl->m_mutex);
-  if (m_impl->m_primarySourceName.empty()) {
+  auto& inst = ::GetInstance();
+  std::scoped_lock lock(inst.m_mutex);
+  if (inst.m_primarySourceName.empty()) {
     return;
   }
-  auto it = m_impl->m_sources.find(m_impl->m_primarySourceName);
-  if (it == m_impl->m_sources.end()) {
+  auto it = inst.m_sources.find(inst.m_primarySourceName);
+  if (it == inst.m_sources.end()) {
     return;
   }
   if (size == kSize160x120) {

cameraserver/src/main/native/cpp/cameraserver/CameraServerShared.cpp

@@ -12,9 +12,12 @@ class DefaultCameraServerShared : public frc::CameraServerShared {
   void ReportUsbCamera(int id) override {}
   void ReportAxisCamera(int id) override {}
   void ReportVideoServer(int id) override {}
-  void SetCameraServerError(const wpi::Twine& error) override {}
-  void SetVisionRunnerError(const wpi::Twine& error) override {}
-  void ReportDriverStationError(const wpi::Twine& error) override {}
+  void SetCameraServerErrorV(fmt::string_view format,
+                             fmt::format_args args) override {}
+  void SetVisionRunnerErrorV(fmt::string_view format,
+                             fmt::format_args args) override {}
+  void ReportDriverStationErrorV(fmt::string_view format,
+                                 fmt::format_args args) override {}
   std::pair<std::thread::id, bool> GetRobotMainThreadId() const override {
     return std::make_pair(std::thread::id(), false);
   }

cameraserver/src/main/native/cpp/vision/VisionRunner.cpp

@@ -33,7 +33,7 @@ void VisionRunnerBase::RunOnce() {
   auto frameTime = m_cvSink.GrabFrame(*m_image);
   if (frameTime == 0) {
     auto error = m_cvSink.GetError();
-    csShared->ReportDriverStationError(error);
+    csShared->ReportDriverStationError(error.c_str());
   } else {
     DoProcess(*m_image);
   }

cameraserver/src/main/native/include/cameraserver/CameraServer.h

@@ -6,11 +6,11 @@
 
 #include <stdint.h>
 
-#include <memory>
 #include <string>
+#include <string_view>
 
-#include <wpi/ArrayRef.h>
-#include <wpi/Twine.h>
+#include <wpi/deprecated.h>
+#include <wpi/span.h>
 
 #include "cscore.h"
 #include "cscore_cv.h"
@@ -31,7 +31,9 @@ class CameraServer {
 
   /**
    * Get the CameraServer instance.
+   * @deprecated Use the static methods
    */
+  WPI_DEPRECATED("Use static methods")
   static CameraServer* GetInstance();
 
   /**
@@ -45,7 +47,7 @@ class CameraServer {
    * with device 0, creating a camera named "USB Camera 0".  Subsequent calls
    * increment the device number (e.g. 1, 2, etc).
    */
-  cs::UsbCamera StartAutomaticCapture();
+  static cs::UsbCamera StartAutomaticCapture();
 
   /**
    * Start automatically capturing images to send to the dashboard.
@@ -55,7 +57,7 @@ class CameraServer {
    *
    * @param dev The device number of the camera interface
    */
-  cs::UsbCamera StartAutomaticCapture(int dev);
+  static cs::UsbCamera StartAutomaticCapture(int dev);
 
   /**
    * Start automatically capturing images to send to the dashboard.
@@ -63,7 +65,7 @@ class CameraServer {
    * @param name The name to give the camera
    * @param dev  The device number of the camera interface
    */
-  cs::UsbCamera StartAutomaticCapture(const wpi::Twine& name, int dev);
+  static cs::UsbCamera StartAutomaticCapture(std::string_view name, int dev);
 
   /**
    * Start automatically capturing images to send to the dashboard.
@@ -71,8 +73,8 @@ class CameraServer {
    * @param name The name to give the camera
    * @param path The device path (e.g. "/dev/video0") of the camera
    */
-  cs::UsbCamera StartAutomaticCapture(const wpi::Twine& name,
-                                      const wpi::Twine& path);
+  static cs::UsbCamera StartAutomaticCapture(std::string_view name,
+                                             std::string_view path);
 
   /**
    * Start automatically capturing images to send to the dashboard from
@@ -80,7 +82,7 @@ class CameraServer {
    *
    * @param camera Camera
    */
-  cs::MjpegServer StartAutomaticCapture(const cs::VideoSource& camera);
+  static cs::MjpegServer StartAutomaticCapture(const cs::VideoSource& camera);
 
   /**
    * Adds an Axis IP camera.
@@ -89,7 +91,7 @@ class CameraServer {
    *
    * @param host Camera host IP or DNS name (e.g. "10.x.y.11")
    */
-  cs::AxisCamera AddAxisCamera(const wpi::Twine& host);
+  static cs::AxisCamera AddAxisCamera(std::string_view host);
 
   /**
    * Adds an Axis IP camera.
@@ -98,7 +100,7 @@ class CameraServer {
    *
    * @param host Camera host IP or DNS name (e.g. "10.x.y.11")
    */
-  cs::AxisCamera AddAxisCamera(const char* host);
+  static cs::AxisCamera AddAxisCamera(const char* host);
 
   /**
    * Adds an Axis IP camera.
@@ -107,7 +109,7 @@ class CameraServer {
    *
    * @param host Camera host IP or DNS name (e.g. "10.x.y.11")
    */
-  cs::AxisCamera AddAxisCamera(const std::string& host);
+  static cs::AxisCamera AddAxisCamera(const std::string& host);
 
   /**
    * Adds an Axis IP camera.
@@ -116,7 +118,7 @@ class CameraServer {
    *
    * @param hosts Array of Camera host IPs/DNS names
    */
-  cs::AxisCamera AddAxisCamera(wpi::ArrayRef<std::string> hosts);
+  static cs::AxisCamera AddAxisCamera(wpi::span<const std::string> hosts);
 
   /**
    * Adds an Axis IP camera.
@@ -126,7 +128,7 @@ class CameraServer {
    * @param hosts Array of Camera host IPs/DNS names
    */
   template <typename T>
-  cs::AxisCamera AddAxisCamera(std::initializer_list<T> hosts);
+  static cs::AxisCamera AddAxisCamera(std::initializer_list<T> hosts);
 
   /**
    * Adds an Axis IP camera.
@@ -134,7 +136,8 @@ class CameraServer {
    * @param name The name to give the camera
    * @param host Camera host IP or DNS name (e.g. "10.x.y.11")
    */
-  cs::AxisCamera AddAxisCamera(const wpi::Twine& name, const wpi::Twine& host);
+  static cs::AxisCamera AddAxisCamera(std::string_view name,
+                                      std::string_view host);
 
   /**
    * Adds an Axis IP camera.
@@ -142,7 +145,7 @@ class CameraServer {
    * @param name The name to give the camera
    * @param host Camera host IP or DNS name (e.g. "10.x.y.11")
    */
-  cs::AxisCamera AddAxisCamera(const wpi::Twine& name, const char* host);
+  static cs::AxisCamera AddAxisCamera(std::string_view name, const char* host);
 
   /**
    * Adds an Axis IP camera.
@@ -150,7 +153,8 @@ class CameraServer {
    * @param name The name to give the camera
    * @param host Camera host IP or DNS name (e.g. "10.x.y.11")
    */
-  cs::AxisCamera AddAxisCamera(const wpi::Twine& name, const std::string& host);
+  static cs::AxisCamera AddAxisCamera(std::string_view name,
+                                      const std::string& host);
 
   /**
    * Adds an Axis IP camera.
@@ -158,8 +162,8 @@ class CameraServer {
    * @param name The name to give the camera
    * @param hosts Array of Camera host IPs/DNS names
    */
-  cs::AxisCamera AddAxisCamera(const wpi::Twine& name,
-                               wpi::ArrayRef<std::string> hosts);
+  static cs::AxisCamera AddAxisCamera(std::string_view name,
+                                      wpi::span<const std::string> hosts);
 
   /**
    * Adds an Axis IP camera.
@@ -168,8 +172,8 @@ class CameraServer {
    * @param hosts Array of Camera host IPs/DNS names
    */
   template <typename T>
-  cs::AxisCamera AddAxisCamera(const wpi::Twine& name,
-                               std::initializer_list<T> hosts);
+  static cs::AxisCamera AddAxisCamera(std::string_view name,
+                                      std::initializer_list<T> hosts);
 
   /**
    * Adds a virtual camera for switching between two streams.  Unlike the
@@ -177,7 +181,7 @@ class CameraServer {
    * VideoSource.  Calling SetSource() on the returned object can be used
    * to switch the actual source of the stream.
    */
-  cs::MjpegServer AddSwitchedCamera(const wpi::Twine& name);
+  static cs::MjpegServer AddSwitchedCamera(std::string_view name);
 
   /**
    * Get OpenCV access to the primary camera feed.  This allows you to
@@ -186,7 +190,7 @@ class CameraServer {
    * <p>This is only valid to call after a camera feed has been added
    * with startAutomaticCapture() or addServer().
    */
-  cs::CvSink GetVideo();
+  static cs::CvSink GetVideo();
 
   /**
    * Get OpenCV access to the specified camera.  This allows you to get
@@ -194,7 +198,7 @@ class CameraServer {
    *
    * @param camera Camera (e.g. as returned by startAutomaticCapture).
    */
-  cs::CvSink GetVideo(const cs::VideoSource& camera);
+  static cs::CvSink GetVideo(const cs::VideoSource& camera);
 
   /**
    * Get OpenCV access to the specified camera.  This allows you to get
@@ -202,7 +206,7 @@ class CameraServer {
    *
    * @param name Camera name
    */
-  cs::CvSink GetVideo(const wpi::Twine& name);
+  static cs::CvSink GetVideo(std::string_view name);
 
   /**
    * Create a MJPEG stream with OpenCV input. This can be called to pass custom
@@ -212,35 +216,35 @@ class CameraServer {
    * @param width Width of the image being sent
    * @param height Height of the image being sent
    */
-  cs::CvSource PutVideo(const wpi::Twine& name, int width, int height);
+  static cs::CvSource PutVideo(std::string_view name, int width, int height);
 
   /**
    * Adds a MJPEG server at the next available port.
    *
    * @param name Server name
    */
-  cs::MjpegServer AddServer(const wpi::Twine& name);
+  static cs::MjpegServer AddServer(std::string_view name);
 
   /**
    * Adds a MJPEG server.
    *
    * @param name Server name
    */
-  cs::MjpegServer AddServer(const wpi::Twine& name, int port);
+  static cs::MjpegServer AddServer(std::string_view name, int port);
 
   /**
    * Adds an already created server.
    *
    * @param server Server
    */
-  void AddServer(const cs::VideoSink& server);
+  static void AddServer(const cs::VideoSink& server);
 
   /**
    * Removes a server by name.
    *
    * @param name Server name
    */
-  void RemoveServer(const wpi::Twine& name);
+  static void RemoveServer(std::string_view name);
 
   /**
    * Get server for the primary camera feed.
@@ -248,28 +252,28 @@ class CameraServer {
    * This is only valid to call after a camera feed has been added with
    * StartAutomaticCapture() or AddServer().
    */
-  cs::VideoSink GetServer();
+  static cs::VideoSink GetServer();
 
   /**
    * Gets a server by name.
    *
    * @param name Server name
    */
-  cs::VideoSink GetServer(const wpi::Twine& name);
+  static cs::VideoSink GetServer(std::string_view name);
 
   /**
    * Adds an already created camera.
    *
    * @param camera Camera
    */
-  void AddCamera(const cs::VideoSource& camera);
+  static void AddCamera(const cs::VideoSource& camera);
 
   /**
    * Removes a camera by name.
    *
    * @param name Camera name
    */
-  void RemoveCamera(const wpi::Twine& name);
+  static void RemoveCamera(std::string_view name);
 
   /**
    * Sets the size of the image to use. Use the public kSize constants to set
@@ -280,14 +284,10 @@ class CameraServer {
    *             StartAutomaticCapture() instead.
    * @param size The size to use
    */
-  void SetSize(int size);
+  static void SetSize(int size);
 
  private:
-  CameraServer();
-  ~CameraServer();
-
-  struct Impl;
-  std::unique_ptr<Impl> m_impl;
+  CameraServer() = default;
 };
 
 }  // namespace frc

cameraserver/src/main/native/include/cameraserver/CameraServer.inc

@@ -19,7 +19,7 @@ inline cs::AxisCamera CameraServer::AddAxisCamera(
 
 template <typename T>
 inline cs::AxisCamera CameraServer::AddAxisCamera(
-    const wpi::Twine& name, std::initializer_list<T> hosts) {
+    std::string_view name, std::initializer_list<T> hosts) {
   std::vector<std::string> vec;
   vec.reserve(hosts.size());
   for (const auto& host : hosts) {

cameraserver/src/main/native/include/cameraserver/CameraServerShared.h

@@ -8,7 +8,7 @@
 #include <thread>
 #include <utility>
 
-#include <wpi/Twine.h>
+#include <fmt/format.h>
 
 namespace frc {
 class CameraServerShared {
@@ -17,10 +17,31 @@ class CameraServerShared {
   virtual void ReportUsbCamera(int id) = 0;
   virtual void ReportAxisCamera(int id) = 0;
   virtual void ReportVideoServer(int id) = 0;
-  virtual void SetCameraServerError(const wpi::Twine& error) = 0;
-  virtual void SetVisionRunnerError(const wpi::Twine& error) = 0;
-  virtual void ReportDriverStationError(const wpi::Twine& error) = 0;
+  virtual void SetCameraServerErrorV(fmt::string_view format,
+                                     fmt::format_args args) = 0;
+  virtual void SetVisionRunnerErrorV(fmt::string_view format,
+                                     fmt::format_args args) = 0;
+  virtual void ReportDriverStationErrorV(fmt::string_view format,
+                                         fmt::format_args args) = 0;
   virtual std::pair<std::thread::id, bool> GetRobotMainThreadId() const = 0;
+
+  template <typename S, typename... Args>
+  inline void SetCameraServerError(const S& format, Args&&... args) {
+    SetCameraServerErrorV(format,
+                          fmt::make_args_checked<Args...>(format, args...));
+  }
+
+  template <typename S, typename... Args>
+  inline void SetVisionRunnerError(const S& format, Args&&... args) {
+    SetVisionRunnerErrorV(format,
+                          fmt::make_args_checked<Args...>(format, args...));
+  }
+
+  template <typename S, typename... Args>
+  inline void ReportDriverStationError(const S& format, Args&&... args) {
+    ReportDriverStationErrorV(format,
+                              fmt::make_args_checked<Args...>(format, args...));
+  }
 };
 
 CameraServerShared* GetCameraServerShared();

cameraserver/src/main/native/include/vision/VisionRunner.h

@@ -49,9 +49,9 @@ class VisionRunnerBase {
   void RunOnce();
 
   /**
-   * A convenience method that calls {@link #runOnce()} in an infinite loop.
-   * This must be run in a dedicated thread, and cannot be used in the main
-   * robot thread because it will freeze the robot program.
+   * A convenience method that calls runOnce() in an infinite loop. This must be
+   * run in a dedicated thread, and cannot be used in the main robot thread
+   * because it will freeze the robot program.
    *
    * <strong>Do not call this method directly from the main thread.</strong>
    */

cmake/scripts/GenResource.cmake

@@ -7,7 +7,7 @@ GET_FILENAME_COMPONENT(inputBase ${input} NAME)
 STRING(REGEX REPLACE "[^a-zA-Z0-9]" "_" funcName "${inputBase}")
 SET(funcName "GetResource_${funcName}")
 
-FILE(WRITE "${output}" "#include <stddef.h>\n#include <wpi/StringRef.h>\nextern \"C\" {\nstatic const unsigned char contents[] = {")
+FILE(WRITE "${output}" "#include <stddef.h>\n#include <string_view>\nextern \"C\" {\nstatic const unsigned char contents[] = {")
 
 STRING(REGEX MATCHALL ".." outputData "${fileHex}")
 STRING(REGEX REPLACE ";" ", 0x" outputData "${outputData}")
@@ -17,7 +17,7 @@ FILE(APPEND "${output}" "const unsigned char* ${prefix}${funcName}(size_t* len)
 IF(NOT namespace STREQUAL "")
   FILE(APPEND "${output}" "namespace ${namespace} {\n")
 ENDIF()
-FILE(APPEND "${output}" "wpi::StringRef ${funcName}() {\n  return wpi::StringRef(reinterpret_cast<const char*>(contents), ${fileSize});\n}\n")
+FILE(APPEND "${output}" "std::string_view ${funcName}() {\n  return std::string_view(reinterpret_cast<const char*>(contents), ${fileSize});\n}\n")
 IF(NOT namespace STREQUAL "")
   FILE(APPEND "${output}" "}\n")
 ENDIF()

crossConnIntegrationTests/build.gradle

@@ -0,0 +1,118 @@
+import org.gradle.language.base.internal.ProjectLayout
+import jaci.gradle.toolchains.*
+import jaci.gradle.nativedeps.*
+import org.gradle.internal.os.OperatingSystem
+
+apply plugin: 'cpp'
+apply plugin: 'visual-studio'
+apply plugin: 'edu.wpi.first.NativeUtils'
+apply plugin: ExtraTasks
+
+apply plugin: 'edu.wpi.first.NativeUtils'
+apply plugin: 'jaci.gradle.EmbeddedTools'
+
+apply from: '../shared/config.gradle'
+
+ext {
+    sharedCvConfigs = [crossConnIntegrationTests: []]
+    staticCvConfigs = [:]
+    useJava = false
+    useCpp = true
+    staticGtestConfigs = [crossConnIntegrationTests: []]
+}
+
+apply from: "${rootDir}/shared/opencv.gradle"
+
+apply from: "${rootDir}/shared/googletest.gradle"
+
+model {
+    components {
+        crossConnIntegrationTests(NativeExecutableSpec) {
+            targetBuildTypes 'debug'
+            nativeUtils.useRequiredLibrary(it, 'googletest_static')
+            binaries.all { binary ->
+                if (binary.targetPlatform.name == nativeUtils.wpi.platforms.roborio) {
+                    binary.sources {
+                        athenaCpp(CppSourceSet) {
+                            source {
+                                srcDirs = ['src/main/native/cpp']
+                                includes = ['**/*.cpp']
+                            }
+                            exportedHeaders {
+                                srcDirs = ['src/main/native/include']
+                                includes = ['**/*.h']
+                            }
+                        }
+                    }
+                    binary.tasks.withType(CppCompile) {
+                        cppCompiler.args "-Wno-missing-field-initializers"
+                        cppCompiler.args "-Wno-unused-variable"
+                        cppCompiler.args "-Wno-error=deprecated-declarations"
+                    }
+                    project(':hal').addHalDependency(binary, 'shared')
+                    project(':hal').addHalJniDependency(binary)
+                    lib project: ':wpiutil', library: 'wpiutil', linkage: 'shared'
+                    if (binary.targetPlatform.name == nativeUtils.wpi.platforms.roborio) {
+                        nativeUtils.useRequiredLibrary(binary, 'netcomm_shared', 'chipobject_shared', 'visa_shared', 'ni_runtime_shared')
+                    }
+                } else {
+                    binary.sources {
+                        simCpp(CppSourceSet) {
+                            source {
+                                srcDirs 'src/main/native/dt'
+                                includes = ['**/*.cpp']
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+deploy {
+    targets {
+        target('roborio') {
+            directory = '/home/admin'
+            maxChannels = 4
+            locations {
+                ssh {
+                    address = "172.22.11.2"
+                    user = 'admin'
+                    password = ''
+                    ipv6 = false
+                }
+            }
+        }
+    }
+    artifacts {
+        all {
+            targets << 'roborio'
+            predeploy << { ctx ->
+                ctx.execute('/usr/local/frc/bin/frcKillRobot.sh -t')
+            }
+            postdeploy << { ctx ->
+                ctx.execute("sync")
+                ctx.execute("ldconfig")
+            }
+        }
+
+        nativeArtifact('crossConnIntegrationTests') {
+            component = 'crossConnIntegrationTests'
+            targetPlatform = nativeUtils.wpi.platforms.roborio
+            libraryDirectory = '/usr/local/frc/third-party/lib'
+            buildType = 'debug'
+            postdeploy << { ctx ->
+                ctx.execute('chmod +x crossConnIntegrationTests')
+            }
+        }
+    }
+}
+
+tasks.register('deployTests') {
+    try {
+        dependsOn tasks.named('deployCrossConnIntegrationTestsLibrariesRoborio')
+        dependsOn tasks.named('deployCrossConnIntegrationTestsRoborio')
+    } catch (ignored) {
+    }
+}

crossConnIntegrationTests/src/main/native/cpp/AnalogTests.cpp

@@ -0,0 +1,112 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <hal/AnalogInput.h>
+#include <hal/AnalogOutput.h>
+#include <wpi/SmallVector.h>
+
+#include "CrossConnects.h"
+#include "LifetimeWrappers.h"
+#include "gtest/gtest.h"
+
+using namespace hlt;
+
+class AnalogCrossTest : public ::testing::TestWithParam<std::pair<int, int>> {};
+
+TEST_P(AnalogCrossTest, TestAnalogCross) {
+  auto param = GetParam();
+
+  int32_t status = 0;
+  AnalogInputHandle input{param.first, &status};
+  ASSERT_EQ(0, status);
+  AnalogOutputHandle output{param.second, &status};
+  ASSERT_EQ(0, status);
+
+  for (double i = 0; i < 5; i += 0.1) {
+    HAL_SetAnalogOutput(output, i, &status);
+    ASSERT_EQ(0, status);
+    usleep(1000);
+    ASSERT_NEAR(i, HAL_GetAnalogVoltage(input, &status), 0.01);
+    ASSERT_EQ(0, status);
+  }
+
+  for (double i = 5; i > 0; i -= 0.1) {
+    HAL_SetAnalogOutput(output, i, &status);
+    ASSERT_EQ(0, status);
+    usleep(1000);
+    ASSERT_NEAR(i, HAL_GetAnalogVoltage(input, &status), 0.01);
+    ASSERT_EQ(0, status);
+  }
+}
+
+TEST(AnalogInputTest, TestAllocateAll) {
+  wpi::SmallVector<AnalogInputHandle, 21> analogHandles;
+  for (int i = 0; i < HAL_GetNumAnalogInputs(); i++) {
+    int32_t status = 0;
+    analogHandles.emplace_back(AnalogInputHandle(i, &status));
+    ASSERT_EQ(status, 0);
+  }
+}
+
+TEST(AnalogInputTest, TestMultipleAllocateFails) {
+  int32_t status = 0;
+  AnalogInputHandle handle(0, &status);
+  ASSERT_NE(handle, HAL_kInvalidHandle);
+  ASSERT_EQ(status, 0);
+
+  AnalogInputHandle handle2(0, &status);
+  ASSERT_EQ(handle2, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_IS_ALLOCATED);
+}
+
+TEST(AnalogInputTest, TestOverAllocateFails) {
+  int32_t status = 0;
+  AnalogInputHandle handle(HAL_GetNumAnalogInputs(), &status);
+  ASSERT_EQ(handle, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_OUT_OF_RANGE);
+}
+
+TEST(AnalogInputTest, TestUnderAllocateFails) {
+  int32_t status = 0;
+  AnalogInputHandle handle(-1, &status);
+  ASSERT_EQ(handle, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_OUT_OF_RANGE);
+}
+
+TEST(AnalogOutputTest, TestAllocateAll) {
+  wpi::SmallVector<AnalogOutputHandle, 21> analogHandles;
+  for (int i = 0; i < HAL_GetNumAnalogOutputs(); i++) {
+    int32_t status = 0;
+    analogHandles.emplace_back(AnalogOutputHandle(i, &status));
+    ASSERT_EQ(status, 0);
+  }
+}
+
+TEST(AnalogOutputTest, TestMultipleAllocateFails) {
+  int32_t status = 0;
+  AnalogOutputHandle handle(0, &status);
+  ASSERT_NE(handle, HAL_kInvalidHandle);
+  ASSERT_EQ(status, 0);
+
+  AnalogOutputHandle handle2(0, &status);
+  ASSERT_EQ(handle2, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_IS_ALLOCATED);
+}
+
+TEST(AnalogOutputTest, TestOverAllocateFails) {
+  int32_t status = 0;
+  AnalogOutputHandle handle(HAL_GetNumAnalogOutputs(), &status);
+  ASSERT_EQ(handle, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_OUT_OF_RANGE);
+}
+
+TEST(AnalogOutputTest, TestUnderAllocateFails) {
+  int32_t status = 0;
+  AnalogOutputHandle handle(-1, &status);
+  ASSERT_EQ(handle, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_OUT_OF_RANGE);
+}
+
+INSTANTIATE_TEST_SUITE_P(AnalogCrossConnectsTest, AnalogCrossTest,
+                         ::testing::ValuesIn(AnalogCrossConnects));

crossConnIntegrationTests/src/main/native/cpp/DIOTests.cpp

@@ -0,0 +1,101 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <hal/DIO.h>
+#include <wpi/SmallVector.h>
+
+#include "CrossConnects.h"
+#include "LifetimeWrappers.h"
+#include "gtest/gtest.h"
+
+using namespace hlt;
+
+class DIOTest : public ::testing::TestWithParam<std::pair<int, int>> {};
+
+TEST_P(DIOTest, TestDIOCross) {
+  auto param = GetParam();
+  int32_t status = 0;
+  DIOHandle first{param.first, false, &status};
+  ASSERT_EQ(0, status);
+  DIOHandle second{param.second, true, &status};
+  ASSERT_EQ(0, status);
+
+  HAL_SetDIO(first, false, &status);
+  ASSERT_EQ(0, status);
+  usleep(1000);
+  ASSERT_FALSE(HAL_GetDIO(first, &status));
+  ASSERT_EQ(0, status);
+  ASSERT_FALSE(HAL_GetDIO(second, &status));
+  ASSERT_EQ(0, status);
+
+  HAL_SetDIO(first, true, &status);
+  ASSERT_EQ(0, status);
+  usleep(1000);
+  ASSERT_TRUE(HAL_GetDIO(second, &status));
+  ASSERT_EQ(0, status);
+
+  HAL_SetDIODirection(first, true, &status);
+  ASSERT_EQ(0, status);
+  HAL_SetDIODirection(second, false, &status);
+  ASSERT_EQ(0, status);
+
+  HAL_SetDIO(second, false, &status);
+  ASSERT_EQ(0, status);
+  usleep(1000);
+  ASSERT_FALSE(HAL_GetDIO(first, &status));
+  ASSERT_EQ(0, status);
+
+  HAL_SetDIO(second, true, &status);
+  ASSERT_EQ(0, status);
+  usleep(1000);
+  ASSERT_TRUE(HAL_GetDIO(first, &status));
+  ASSERT_EQ(0, status);
+}
+
+TEST(DIOTest, TestAllocateAll) {
+  wpi::SmallVector<DIOHandle, 32> dioHandles;
+  for (int i = 0; i < HAL_GetNumDigitalChannels(); i++) {
+    int32_t status = 0;
+    dioHandles.emplace_back(i, true, &status);
+    ASSERT_EQ(status, 0);
+  }
+}
+
+TEST(DIOTest, TestMultipleAllocateFails) {
+  int32_t status = 0;
+  DIOHandle handle(0, true, &status);
+  ASSERT_NE(handle, HAL_kInvalidHandle);
+  ASSERT_EQ(status, 0);
+
+  DIOHandle handle2(0, true, &status);
+  ASSERT_EQ(handle2, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_IS_ALLOCATED);
+}
+
+TEST(DIOTest, TestOverAllocateFails) {
+  int32_t status = 0;
+  DIOHandle handle(HAL_GetNumDigitalChannels(), true, &status);
+  ASSERT_EQ(handle, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_OUT_OF_RANGE);
+}
+
+TEST(DIOTest, TestUnderAllocateFails) {
+  int32_t status = 0;
+  DIOHandle handle(-1, true, &status);
+  ASSERT_EQ(handle, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_OUT_OF_RANGE);
+}
+
+TEST(DIOTest, TestCrossAllocationFails) {
+  int32_t status = 0;
+  PWMHandle pwmHandle(10, &status);
+  ASSERT_NE(pwmHandle, HAL_kInvalidHandle);
+  ASSERT_EQ(status, 0);
+  DIOHandle handle(10, true, &status);
+  ASSERT_EQ(handle, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_IS_ALLOCATED);
+}
+
+INSTANTIATE_TEST_SUITE_P(DIOCrossConnectsTest, DIOTest,
+                         ::testing::ValuesIn(DIOCrossConnects));

crossConnIntegrationTests/src/main/native/cpp/DutyCycleTests.cpp

@@ -0,0 +1,51 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <hal/HAL.h>
+
+#include "CrossConnects.h"
+#include "LifetimeWrappers.h"
+#include "gtest/gtest.h"
+
+using namespace hlt;
+
+class DutyCycleTest : public ::testing::TestWithParam<std::pair<int, int>> {};
+
+TEST_P(DutyCycleTest, TestDutyCycle) {
+  auto param = GetParam();
+
+  int32_t status = 0;
+  PWMHandle pwmHandle(param.first, &status);
+  ASSERT_NE(pwmHandle, HAL_kInvalidHandle);
+  ASSERT_EQ(0, status);
+
+  // Ensure our PWM is disabled, and set up properly
+  HAL_SetPWMRaw(pwmHandle, 0, &status);
+  ASSERT_EQ(0, status);
+  HAL_SetPWMConfig(pwmHandle, 2.0, 1.0, 1.0, 0, 0, &status);
+  HAL_SetPWMConfig(pwmHandle, 5.05, 2.525, 2.525, 2.525, 0, &status);
+  ASSERT_EQ(0, status);
+  HAL_SetPWMPeriodScale(pwmHandle, 0, &status);
+  ASSERT_EQ(0, status);
+
+  DIOHandle dioHandle{param.second, true, &status};
+  ASSERT_EQ(0, status);
+
+  DutyCycleHandle dutyCycle{dioHandle, &status};
+  ASSERT_EQ(0, status);
+
+  HAL_SetPWMSpeed(pwmHandle, 0.5, &status);
+  ASSERT_EQ(0, status);
+
+  // Sleep enough time for the frequency to converge
+  usleep(3500000);
+
+  ASSERT_NEAR(1000 / 5.05,
+              (double)HAL_GetDutyCycleFrequency(dutyCycle, &status), 1);
+
+  // TODO measure output
+}
+
+INSTANTIATE_TEST_SUITE_P(DutyCycleCrossConnTest, DutyCycleTest,
+                         ::testing::ValuesIn(PWMCrossConnects));

crossConnIntegrationTests/src/main/native/cpp/Main.cpp

@@ -5,7 +5,6 @@
 #include "gtest/gtest.h"
 
 int main(int argc, char** argv) {
-  ::testing::InitGoogleTest(&argc, argv);
-  int ret = RUN_ALL_TESTS();
-  return ret;
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
 }

crossConnIntegrationTests/src/main/native/cpp/PWMTests.cpp

@@ -0,0 +1,357 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <atomic>
+#include <thread>
+
+#include <hal/DMA.h>
+#include <hal/HAL.h>
+#include <wpi/SmallVector.h>
+#include <wpi/condition_variable.h>
+#include <wpi/priority_mutex.h>
+
+#include "CrossConnects.h"
+#include "LifetimeWrappers.h"
+#include "gtest/gtest.h"
+
+using namespace hlt;
+
+class PWMTest : public ::testing::TestWithParam<std::pair<int, int>> {};
+
+void TestTimingDMA(int squelch, std::pair<int, int> param) {
+  // Initialize DMA
+  int32_t status = 0;
+  DMAHandle dmaHandle(&status);
+  ASSERT_NE(dmaHandle, HAL_kInvalidHandle);
+  ASSERT_EQ(0, status);
+
+  status = 0;
+  PWMHandle pwmHandle(param.first, &status);
+  ASSERT_NE(pwmHandle, HAL_kInvalidHandle);
+  ASSERT_EQ(0, status);
+
+  // Ensure our PWM is disabled, and set up properly
+  HAL_SetPWMRaw(pwmHandle, 0, &status);
+  HAL_SetPWMConfig(pwmHandle, 2.0, 1.0, 1.0, 0, 0, &status);
+  HAL_SetPWMPeriodScale(pwmHandle, squelch, &status);
+
+  unsigned int checkPeriod = 0;
+  switch (squelch) {
+    case (0):
+      checkPeriod = 5050;
+      break;
+    case (1):
+      checkPeriod = 10100;
+      break;
+    case (3):
+      checkPeriod = 20200;
+      break;
+  }
+
+  status = 0;
+  DIOHandle dioHandle(param.second, true, &status);
+  ASSERT_NE(dioHandle, HAL_kInvalidHandle);
+
+  HAL_AddDMADigitalSource(dmaHandle, dioHandle, &status);
+  ASSERT_EQ(0, status);
+
+  HAL_SetDMAExternalTrigger(dmaHandle, dioHandle,
+                            HAL_AnalogTriggerType::HAL_Trigger_kInWindow, true,
+                            true, &status);
+  ASSERT_EQ(0, status);
+
+  // Loop to test 5 speeds
+  for (unsigned int testWidth = 1000; testWidth < 2100; testWidth += 250) {
+    HAL_StartDMA(dmaHandle, 1024, &status);
+    ASSERT_EQ(0, status);
+
+    while (true) {
+      int32_t remaining = 0;
+      HAL_DMASample testSample;
+      HAL_ReadDMA(dmaHandle, &testSample, 0.01, &remaining, &status);
+      if (remaining == 0) {
+        break;
+      }
+    }
+
+    HAL_SetPWMSpeed(pwmHandle, (testWidth - 1000) / 1000.0, &status);
+
+    constexpr const int kSampleCount = 15;
+    HAL_DMASample dmaSamples[kSampleCount];
+    int readCount = 0;
+    while (readCount < kSampleCount) {
+      status = 0;
+      int32_t remaining = 0;
+      HAL_DMAReadStatus readStatus = HAL_ReadDMA(
+          dmaHandle, &dmaSamples[readCount], 1.0, &remaining, &status);
+      ASSERT_EQ(0, status);
+      ASSERT_EQ(HAL_DMAReadStatus::HAL_DMA_OK, readStatus);
+      readCount++;
+    }
+
+    HAL_SetPWMSpeed(pwmHandle, 0, &status);
+    HAL_StopDMA(dmaHandle, &status);
+
+    // Find first rising edge
+    int startIndex = 4;
+    while (startIndex < 6) {
+      status = 0;
+      auto value = HAL_GetDMASampleDigitalSource(&dmaSamples[startIndex],
+                                                 dioHandle, &status);
+      ASSERT_EQ(0, status);
+      if (value)
+        break;
+      startIndex++;
+    }
+    ASSERT_LT(startIndex, 6);
+
+    // Check that samples alternate
+    bool previous = false;
+    int iterationCount = 0;
+    for (int i = startIndex; i < startIndex + 8; i++) {
+      auto value =
+          HAL_GetDMASampleDigitalSource(&dmaSamples[i], dioHandle, &status);
+      ASSERT_EQ(0, status);
+      ASSERT_NE(previous, value);
+      previous = !previous;
+      iterationCount++;
+    }
+    ASSERT_EQ(iterationCount, 8);
+    iterationCount = 0;
+
+    // Check width between samples
+    for (int i = startIndex; i < startIndex + 8; i += 2) {
+      auto width = HAL_GetDMASampleTime(&dmaSamples[i + 1], &status) -
+                   HAL_GetDMASampleTime(&dmaSamples[i], &status);
+      ASSERT_NEAR(testWidth, width, 10);
+      iterationCount++;
+    }
+    ASSERT_EQ(iterationCount, 4);
+    iterationCount = 0;
+
+    // Check period between samples
+    for (int i = startIndex; i < startIndex + 6; i += 2) {
+      auto period = HAL_GetDMASampleTime(&dmaSamples[i + 2], &status) -
+                    HAL_GetDMASampleTime(&dmaSamples[i], &status);
+      ASSERT_NEAR(checkPeriod, period, 10);
+      iterationCount++;
+    }
+    ASSERT_EQ(iterationCount, 3);
+  }
+}
+
+struct InterruptCheckData {
+  wpi::SmallVector<uint64_t, 8> risingStamps;
+  wpi::SmallVector<uint64_t, 8> fallingStamps;
+  wpi::priority_mutex mutex;
+  wpi::condition_variable cond;
+  HAL_InterruptHandle handle;
+};
+
+// TODO switch this to DMA
+void TestTiming(int squelch, std::pair<int, int> param) {
+  // Initialize interrupt
+  int32_t status = 0;
+  InterruptHandle interruptHandle(&status);
+  // Ensure we have a valid interrupt handle
+  ASSERT_NE(interruptHandle, HAL_kInvalidHandle);
+
+  status = 0;
+  PWMHandle pwmHandle(param.first, &status);
+  ASSERT_NE(pwmHandle, HAL_kInvalidHandle);
+
+  // Ensure our PWM is disabled, and set up properly
+  HAL_SetPWMRaw(pwmHandle, 0, &status);
+  HAL_SetPWMConfig(pwmHandle, 2.0, 1.0, 1.0, 0, 0, &status);
+  HAL_SetPWMPeriodScale(pwmHandle, squelch, &status);
+
+  unsigned int checkPeriod = 0;
+  switch (squelch) {
+    case (0):
+      checkPeriod = 5050;
+      break;
+    case (1):
+      checkPeriod = 10100;
+      break;
+    case (3):
+      checkPeriod = 20200;
+      break;
+  }
+
+  status = 0;
+  DIOHandle dioHandle(param.second, true, &status);
+  ASSERT_NE(dioHandle, HAL_kInvalidHandle);
+
+  InterruptCheckData interruptData;
+  interruptData.handle = interruptHandle;
+
+  // Can use any type for the interrupt handle
+  HAL_RequestInterrupts(interruptHandle, dioHandle,
+                        HAL_AnalogTriggerType::HAL_Trigger_kInWindow, &status);
+
+  HAL_SetInterruptUpSourceEdge(interruptHandle, true, true, &status);
+
+  // Loop to test 5 speeds
+  for (unsigned int i = 1000; i < 2100; i += 250) {
+    interruptData.risingStamps.clear();
+    interruptData.fallingStamps.clear();
+
+    std::atomic_bool runThread{true};
+
+    status = 0;
+    std::thread interruptThread([&]() {
+      while (runThread) {
+        int32_t threadStatus = 0;
+        auto mask =
+            HAL_WaitForInterrupt(interruptHandle, 5, true, &threadStatus);
+
+        if ((mask & 0x100) == 0x100 && interruptData.risingStamps.size() == 0 &&
+            interruptData.fallingStamps.size() == 0) {
+          // Falling edge at start of tracking. Skip
+          continue;
+        }
+
+        int32_t status = 0;
+        if ((mask & 0x1) == 0x1) {
+          auto ts = HAL_ReadInterruptRisingTimestamp(interruptHandle, &status);
+          // Rising Edge
+          interruptData.risingStamps.push_back(ts);
+        } else if ((mask & 0x100) == 0x100) {
+          auto ts = HAL_ReadInterruptFallingTimestamp(interruptHandle, &status);
+          // Falling Edge
+          interruptData.fallingStamps.push_back(ts);
+        }
+
+        if (interruptData.risingStamps.size() >= 4 &&
+            interruptData.fallingStamps.size() >= 4) {
+          interruptData.cond.notify_all();
+          runThread = false;
+          break;
+        }
+      }
+    });
+
+    // Ensure our interrupt actually got created correctly.
+    ASSERT_EQ(status, 0);
+    HAL_SetPWMSpeed(pwmHandle, (i - 1000) / 1000.0, &status);
+    ASSERT_EQ(status, 0);
+    {
+      std::unique_lock<wpi::priority_mutex> lock(interruptData.mutex);
+      // Wait for lock
+      // TODO: Add Timeout
+      auto timeout = interruptData.cond.wait_for(lock, std::chrono::seconds(2));
+      if (timeout == std::cv_status::timeout) {
+        runThread = false;
+        if (interruptThread.joinable()) {
+          interruptThread.join();
+        }
+        ASSERT_TRUE(false);  // Exit test as failure on timeout
+      }
+    }
+
+    HAL_SetPWMRaw(pwmHandle, 0, &status);
+
+    // Ensure our interrupts have the proper counts
+    ASSERT_EQ(interruptData.risingStamps.size(),
+              interruptData.fallingStamps.size());
+
+    ASSERT_GT(interruptData.risingStamps.size(), 0u);
+
+    ASSERT_EQ(interruptData.risingStamps.size() % 2, 0u);
+    ASSERT_EQ(interruptData.fallingStamps.size() % 2, 0u);
+
+    for (size_t j = 0; j < interruptData.risingStamps.size(); j++) {
+      uint64_t width =
+          interruptData.fallingStamps[j] - interruptData.risingStamps[j];
+      ASSERT_NEAR(width, i, 10);
+    }
+
+    for (unsigned int j = 0; j < interruptData.risingStamps.size() - 1; j++) {
+      uint64_t period =
+          interruptData.risingStamps[j + 1] - interruptData.risingStamps[j];
+      ASSERT_NEAR(period, checkPeriod, 10);
+    }
+    runThread = false;
+    if (interruptThread.joinable()) {
+      interruptThread.join();
+    }
+  }
+}
+
+TEST_P(PWMTest, TestTiming4x) {
+  auto param = GetParam();
+  TestTiming(3, param);
+}
+
+TEST_P(PWMTest, TestTiming2x) {
+  auto param = GetParam();
+  TestTiming(1, param);
+}
+
+TEST_P(PWMTest, TestTiming1x) {
+  auto param = GetParam();
+  TestTiming(0, param);
+}
+
+TEST_P(PWMTest, TestTimingDMA4x) {
+  auto param = GetParam();
+  TestTimingDMA(3, param);
+}
+
+TEST_P(PWMTest, TestTimingDMA2x) {
+  auto param = GetParam();
+  TestTimingDMA(1, param);
+}
+
+TEST_P(PWMTest, TestTimingDMA1x) {
+  auto param = GetParam();
+  TestTimingDMA(0, param);
+}
+
+TEST(PWMTest, TestAllocateAll) {
+  wpi::SmallVector<PWMHandle, 21> pwmHandles;
+  for (int i = 0; i < HAL_GetNumPWMChannels(); i++) {
+    int32_t status = 0;
+    pwmHandles.emplace_back(PWMHandle(i, &status));
+    ASSERT_EQ(status, 0);
+  }
+}
+
+TEST(PWMTest, TestMultipleAllocateFails) {
+  int32_t status = 0;
+  PWMHandle handle(0, &status);
+  ASSERT_NE(handle, HAL_kInvalidHandle);
+  ASSERT_EQ(status, 0);
+
+  PWMHandle handle2(0, &status);
+  ASSERT_EQ(handle2, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_IS_ALLOCATED);
+}
+
+TEST(PWMTest, TestOverAllocateFails) {
+  int32_t status = 0;
+  PWMHandle handle(HAL_GetNumPWMChannels(), &status);
+  ASSERT_EQ(handle, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_OUT_OF_RANGE);
+}
+
+TEST(PWMTest, TestUnderAllocateFails) {
+  int32_t status = 0;
+  PWMHandle handle(-1, &status);
+  ASSERT_EQ(handle, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_OUT_OF_RANGE);
+}
+
+TEST(PWMTest, TestCrossAllocationFails) {
+  int32_t status = 0;
+  DIOHandle dioHandle(10, true, &status);
+  ASSERT_NE(dioHandle, HAL_kInvalidHandle);
+  ASSERT_EQ(status, 0);
+  PWMHandle handle(10, &status);
+  ASSERT_EQ(handle, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_IS_ALLOCATED);
+}
+
+INSTANTIATE_TEST_SUITE_P(PWMCrossConnectTests, PWMTest,
+                         ::testing::ValuesIn(PWMCrossConnects));

crossConnIntegrationTests/src/main/native/cpp/RelayAnalogTests.cpp

@@ -0,0 +1,50 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <hal/AnalogInput.h>
+#include <hal/Relay.h>
+#include <wpi/SmallVector.h>
+
+#include "CrossConnects.h"
+#include "LifetimeWrappers.h"
+#include "gtest/gtest.h"
+
+using namespace hlt;
+
+class RelayAnalogTest : public ::testing::TestWithParam<std::pair<int, int>> {};
+
+TEST_P(RelayAnalogTest, TestRelayAnalogCross) {
+  auto param = GetParam();
+
+  int32_t status = 0;
+  RelayHandle relay{param.first, true, &status};
+  ASSERT_EQ(0, status);
+  AnalogInputHandle analog{param.second, &status};
+  ASSERT_EQ(0, status);
+  AnalogTriggerHandle trigger{analog, &status};
+  ASSERT_EQ(0, status);
+  HAL_SetAnalogTriggerLimitsVoltage(trigger, 1.5, 3.0, &status);
+  ASSERT_EQ(0, status);
+
+  HAL_SetRelay(relay, false, &status);
+  ASSERT_EQ(0, status);
+  usleep(1000);
+  ASSERT_FALSE(HAL_GetAnalogTriggerTriggerState(trigger, &status));
+  ASSERT_EQ(0, status);
+
+  HAL_SetRelay(relay, true, &status);
+  ASSERT_EQ(0, status);
+  usleep(1000);
+  ASSERT_TRUE(HAL_GetAnalogTriggerTriggerState(trigger, &status));
+  ASSERT_EQ(0, status);
+
+  HAL_SetRelay(relay, false, &status);
+  ASSERT_EQ(0, status);
+  usleep(1000);
+  ASSERT_FALSE(HAL_GetAnalogTriggerTriggerState(trigger, &status));
+  ASSERT_EQ(0, status);
+}
+
+INSTANTIATE_TEST_SUITE_P(RelayAnalogCrossConnectsTest, RelayAnalogTest,
+                         ::testing::ValuesIn(RelayAnalogCrossConnects));

crossConnIntegrationTests/src/main/native/cpp/RelayDigitalTests.cpp

@@ -0,0 +1,104 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <hal/Relay.h>
+#include <wpi/SmallVector.h>
+
+#include "CrossConnects.h"
+#include "LifetimeWrappers.h"
+#include "gtest/gtest.h"
+
+using namespace hlt;
+
+class RelayDigitalTest : public ::testing::TestWithParam<RelayCross> {};
+
+TEST_P(RelayDigitalTest, TestRelayCross) {
+  auto param = GetParam();
+  int32_t status = 0;
+  RelayHandle fwd{param.Relay, true, &status};
+  ASSERT_EQ(0, status);
+  RelayHandle rev{param.Relay, false, &status};
+  ASSERT_EQ(0, status);
+  DIOHandle fwdInput{param.FwdDio, true, &status};
+  ASSERT_EQ(0, status);
+  DIOHandle revInput{param.RevDio, true, &status};
+  ASSERT_EQ(0, status);
+
+  HAL_SetRelay(fwd, false, &status);
+  ASSERT_EQ(0, status);
+  HAL_SetRelay(rev, false, &status);
+  ASSERT_EQ(0, status);
+  usleep(1000);
+  ASSERT_FALSE(HAL_GetDIO(fwdInput, &status));
+  ASSERT_EQ(0, status);
+  ASSERT_FALSE(HAL_GetDIO(revInput, &status));
+  ASSERT_EQ(0, status);
+
+  HAL_SetRelay(fwd, false, &status);
+  ASSERT_EQ(0, status);
+  HAL_SetRelay(rev, true, &status);
+  ASSERT_EQ(0, status);
+  usleep(1000);
+  ASSERT_FALSE(HAL_GetDIO(fwdInput, &status));
+  ASSERT_EQ(0, status);
+  ASSERT_TRUE(HAL_GetDIO(revInput, &status));
+  ASSERT_EQ(0, status);
+
+  HAL_SetRelay(fwd, true, &status);
+  ASSERT_EQ(0, status);
+  HAL_SetRelay(rev, false, &status);
+  ASSERT_EQ(0, status);
+  usleep(1000);
+  ASSERT_TRUE(HAL_GetDIO(fwdInput, &status));
+  ASSERT_EQ(0, status);
+  ASSERT_FALSE(HAL_GetDIO(revInput, &status));
+  ASSERT_EQ(0, status);
+
+  HAL_SetRelay(fwd, true, &status);
+  ASSERT_EQ(0, status);
+  HAL_SetRelay(rev, true, &status);
+  ASSERT_EQ(0, status);
+  usleep(1000);
+  ASSERT_TRUE(HAL_GetDIO(fwdInput, &status));
+  ASSERT_EQ(0, status);
+  ASSERT_TRUE(HAL_GetDIO(revInput, &status));
+  ASSERT_EQ(0, status);
+}
+
+TEST(RelayDigitalTest, TestAllocateAll) {
+  wpi::SmallVector<RelayHandle, 32> relayHandles;
+  for (int i = 0; i < HAL_GetNumRelayChannels(); i++) {
+    int32_t status = 0;
+    relayHandles.emplace_back(i / 2, i % 2, &status);
+    ASSERT_EQ(status, 0);
+  }
+}
+
+TEST(RelayDigitalTest, TestMultipleAllocateFails) {
+  int32_t status = 0;
+  RelayHandle handle(0, true, &status);
+  ASSERT_NE(handle, HAL_kInvalidHandle);
+  ASSERT_EQ(status, 0);
+
+  RelayHandle handle2(0, true, &status);
+  ASSERT_EQ(handle2, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_IS_ALLOCATED);
+}
+
+TEST(RelayDigitalTest, TestOverAllocateFails) {
+  int32_t status = 0;
+  RelayHandle handle(HAL_GetNumRelayChannels(), true, &status);
+  ASSERT_EQ(handle, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_OUT_OF_RANGE);
+}
+
+TEST(RelayDigitalTest, TestUnderAllocateFails) {
+  int32_t status = 0;
+  RelayHandle handle(-1, true, &status);
+  ASSERT_EQ(handle, HAL_kInvalidHandle);
+  ASSERT_LAST_ERROR_STATUS(status, RESOURCE_OUT_OF_RANGE);
+}
+
+INSTANTIATE_TEST_SUITE_P(RelayDigitalCrossConnectsTest, RelayDigitalTest,
+                         ::testing::ValuesIn(RelayCrossConnects));

crossConnIntegrationTests/src/main/native/cpp/TestEnvironment.cpp

@@ -0,0 +1,71 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <cstdlib>
+#include <thread>
+
+#include <fmt/core.h>
+#include <hal/HAL.h>
+
+#include "gtest/gtest.h"
+#include "mockds/MockDS.h"
+
+using namespace std::chrono_literals;
+
+class TestEnvironment : public testing::Environment {
+  bool m_alreadySetUp = false;
+  MockDS m_mockDS;
+
+ public:
+  TestEnvironment() {
+    // Only set up once. This allows gtest_repeat to be used to automatically
+    // repeat tests.
+    if (m_alreadySetUp) {
+      return;
+    }
+    m_alreadySetUp = true;
+
+    if (!HAL_Initialize(500, 0)) {
+      fmt::print(stderr, "FATAL ERROR: HAL could not be initialized\n");
+      std::exit(-1);
+    }
+
+    m_mockDS.Start();
+
+    // This sets up the network communications library to enable the driver
+    // station. After starting network coms, it will loop until the driver
+    // station returns that the robot is enabled, to ensure that tests will be
+    // able to run on the hardware.
+    HAL_ObserveUserProgramStarting();
+
+    fmt::print("Started coms\n");
+
+    int enableCounter = 0;
+
+    auto checkEnabled = []() {
+      HAL_ControlWord controlWord;
+      std::memset(&controlWord, 0, sizeof(controlWord));
+      HAL_GetControlWord(&controlWord);
+      return controlWord.enabled && controlWord.dsAttached;
+    };
+    while (!checkEnabled()) {
+      if (enableCounter > 50) {
+        // Robot did not enable properly after 5 seconds.
+        // Force exit
+        fmt::print(stderr, " Failed to enable. Aborting\n");
+        std::terminate();
+      }
+
+      std::this_thread::sleep_for(100ms);
+
+      fmt::print("Waiting for enable: {}\n", enableCounter++);
+    }
+    std::this_thread::sleep_for(500ms);
+  }
+
+  ~TestEnvironment() override { m_mockDS.Stop(); }
+};
+
+testing::Environment* const environment =
+    testing::AddGlobalTestEnvironment(new TestEnvironment);

crossConnIntegrationTests/src/main/native/cpp/mockds/MockDS.cpp

@@ -0,0 +1,86 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "MockDS.h"
+
+#include <stdint.h>
+
+#include <string_view>
+
+#include <fmt/core.h>
+#include <hal/cpp/fpga_clock.h>
+#include <wpi/Logger.h>
+#include <wpi/SmallVector.h>
+#include <wpi/UDPClient.h>
+
+static void LoggerFunc(unsigned int level, const char* file, unsigned int line,
+                       const char* msg) {
+  if (level == 20) {
+    fmt::print(stderr, "DS: {}\n", msg);
+    return;
+  }
+
+  std::string_view levelmsg;
+  if (level >= 50) {
+    levelmsg = "CRITICAL";
+  } else if (level >= 40) {
+    levelmsg = "ERROR";
+  } else if (level >= 30) {
+    levelmsg = "WARNING";
+  } else {
+    return;
+  }
+  fmt::print(stderr, "DS: {}: {} ({}:{})\n", levelmsg, msg, file, line);
+}
+
+static void generateEnabledDsPacket(wpi::SmallVectorImpl<uint8_t>& data,
+                                    uint16_t sendCount) {
+  data.clear();
+  data.push_back(sendCount >> 8);
+  data.push_back(sendCount);
+  data.push_back(0x01);  // general data tag
+  data.push_back(0x04);  // teleop enabled
+  data.push_back(0x10);  // normal data request
+  data.push_back(0x00);  // red 1 station
+}
+
+void MockDS::Start() {
+  if (m_active) {
+    return;
+  }
+  m_active = true;
+  m_thread = std::thread([&]() {
+    wpi::Logger logger(LoggerFunc);
+    wpi::UDPClient client(logger);
+    client.start();
+    auto timeout_time = hal::fpga_clock::now();
+    int initCount = 0;
+    uint16_t sendCount = 0;
+    wpi::SmallVector<uint8_t, 8> data;
+    while (m_active) {
+      // Keep 20ms intervals, and increase time to next interval
+      auto current = hal::fpga_clock::now();
+      while (timeout_time <= current) {
+        timeout_time += std::chrono::milliseconds(20);
+      }
+      std::this_thread::sleep_until(timeout_time);
+      generateEnabledDsPacket(data, sendCount++);
+      // ~10 disabled packets are required to make the robot actually enable
+      // 1 is definitely not enough.
+      if (initCount < 10) {
+        initCount++;
+        data[3] = 0;
+      }
+      client.send(data, "127.0.0.1", 1110);
+    }
+    client.shutdown();
+  });
+}
+
+void MockDS::Stop() {
+  m_active = false;
+  if (m_thread.joinable()) {
+    m_thread.join();
+  }
+}

crossConnIntegrationTests/src/main/native/cpp/mockds/MockDS.h

@@ -0,0 +1,23 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#include <atomic>
+#include <thread>
+
+class MockDS {
+ public:
+  MockDS() = default;
+  ~MockDS() { Stop(); }
+  MockDS(const MockDS& other) = delete;
+  MockDS& operator=(const MockDS& other) = delete;
+
+  void Start();
+  void Stop();
+
+ private:
+  std::thread m_thread;
+  std::atomic_bool m_active{false};
+};

crossConnIntegrationTests/src/main/native/include/CrossConnects.h

@@ -0,0 +1,62 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#include <array>
+#include <utility>
+
+namespace hlt {
+
+constexpr static std::array<std::pair<int, int>, 22> DIOCrossConnects{
+    std::pair{20, 25},
+    std::pair{19, 24},
+    std::pair{17, 13},
+    std::pair{16, 12},
+    std::pair{15, 11},
+    std::pair{14, 10},
+    std::pair{26, 2},
+    std::pair{27, 1},
+    std::pair{28, 0},
+    std::pair{29, 3},
+    std::pair{30, 4},
+
+    // Opposite direction
+    std::pair{25, 20},
+    std::pair{24, 19},
+    std::pair{13, 17},
+    std::pair{12, 16},
+    std::pair{11, 15},
+    std::pair{10, 14},
+    std::pair{2, 26},
+    std::pair{1, 27},
+    std::pair{0, 28},
+    std::pair{3, 29},
+    std::pair{4, 30},
+};
+
+// PWM on left, DIO on right
+constexpr static std::array<std::pair<int, int>, 2> PWMCrossConnects{
+    std::pair{0, 18},
+    std::pair{16, 25},
+};
+
+// FWD only, relay on left
+constexpr static std::array<std::pair<int, int>, 2> RelayAnalogCrossConnects{
+    std::pair{2, 0}, std::pair{3, 1}};
+
+struct RelayCross {
+  int Relay;
+  int FwdDio;
+  int RevDio;
+};
+
+constexpr static std::array<RelayCross, 1> RelayCrossConnects{
+    RelayCross{0, 23, 22}};
+
+// input on left
+constexpr static std::array<std::pair<int, int>, 2> AnalogCrossConnects{
+    std::pair{2, 0}, std::pair{4, 1}};
+
+}  // namespace hlt

crossConnIntegrationTests/src/main/native/include/LifetimeWrappers.h

@@ -0,0 +1,200 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#include <hal/DMA.h>
+#include <hal/DutyCycle.h>
+#include <hal/HAL.h>
+
+namespace hlt {
+
+struct InterruptHandle {
+ public:
+  explicit InterruptHandle(int32_t* status) {
+    handle = HAL_InitializeInterrupts(status);
+  }
+  InterruptHandle(const InterruptHandle&) = delete;
+  InterruptHandle operator=(const InterruptHandle&) = delete;
+
+  InterruptHandle(InterruptHandle&&) = default;
+  InterruptHandle& operator=(InterruptHandle&&) = default;
+
+  ~InterruptHandle() { HAL_CleanInterrupts(handle); }
+
+  operator HAL_InterruptHandle() const { return handle; }
+
+ private:
+  HAL_InterruptHandle handle = 0;
+};
+
+struct DMAHandle {
+ public:
+  explicit DMAHandle(int32_t* status) { handle = HAL_InitializeDMA(status); }
+  DMAHandle(const DMAHandle&) = delete;
+  DMAHandle operator=(const DMAHandle&) = delete;
+
+  DMAHandle(DMAHandle&&) = default;
+  DMAHandle& operator=(DMAHandle&&) = default;
+
+  ~DMAHandle() { HAL_FreeDMA(handle); }
+
+  operator HAL_DMAHandle() const { return handle; }
+
+ private:
+  HAL_DMAHandle handle = 0;
+};
+
+struct AnalogInputHandle {
+ public:
+  AnalogInputHandle(int32_t port, int32_t* status) {
+    handle = HAL_InitializeAnalogInputPort(HAL_GetPort(port), nullptr, status);
+  }
+  AnalogInputHandle(const AnalogInputHandle&) = delete;
+  AnalogInputHandle operator=(const AnalogInputHandle&) = delete;
+
+  AnalogInputHandle(AnalogInputHandle&&) = default;
+  AnalogInputHandle& operator=(AnalogInputHandle&&) = default;
+
+  ~AnalogInputHandle() { HAL_FreeAnalogInputPort(handle); }
+
+  operator HAL_AnalogInputHandle() const { return handle; }
+
+ private:
+  HAL_AnalogInputHandle handle = 0;
+};
+
+struct AnalogOutputHandle {
+ public:
+  AnalogOutputHandle(int32_t port, int32_t* status) {
+    handle = HAL_InitializeAnalogOutputPort(HAL_GetPort(port), nullptr, status);
+  }
+  AnalogOutputHandle(const AnalogOutputHandle&) = delete;
+  AnalogOutputHandle operator=(const AnalogOutputHandle&) = delete;
+
+  AnalogOutputHandle(AnalogOutputHandle&&) = default;
+  AnalogOutputHandle& operator=(AnalogOutputHandle&&) = default;
+
+  ~AnalogOutputHandle() { HAL_FreeAnalogOutputPort(handle); }
+
+  operator HAL_AnalogOutputHandle() const { return handle; }
+
+ private:
+  HAL_AnalogOutputHandle handle = 0;
+};
+
+struct AnalogTriggerHandle {
+ public:
+  explicit AnalogTriggerHandle(HAL_AnalogInputHandle port, int32_t* status) {
+    handle = HAL_InitializeAnalogTrigger(port, status);
+  }
+  AnalogTriggerHandle(const AnalogTriggerHandle&) = delete;
+  AnalogTriggerHandle operator=(const AnalogTriggerHandle&) = delete;
+
+  AnalogTriggerHandle(AnalogTriggerHandle&&) = default;
+  AnalogTriggerHandle& operator=(AnalogTriggerHandle&&) = default;
+
+  ~AnalogTriggerHandle() {
+    int32_t status = 0;
+    HAL_CleanAnalogTrigger(handle, &status);
+  }
+
+  operator HAL_AnalogTriggerHandle() const { return handle; }
+
+ private:
+  HAL_AnalogTriggerHandle handle = 0;
+};
+
+struct DutyCycleHandle {
+ public:
+  DutyCycleHandle(HAL_DigitalHandle port, int32_t* status) {
+    handle = HAL_InitializeDutyCycle(
+        port, HAL_AnalogTriggerType::HAL_Trigger_kInWindow, status);
+  }
+  DutyCycleHandle(const DutyCycleHandle&) = delete;
+  DutyCycleHandle operator=(const DutyCycleHandle&) = delete;
+
+  DutyCycleHandle(DutyCycleHandle&&) = default;
+  DutyCycleHandle& operator=(DutyCycleHandle&&) = default;
+
+  ~DutyCycleHandle() { HAL_FreeDutyCycle(handle); }
+
+  operator HAL_DutyCycleHandle() const { return handle; }
+
+ private:
+  HAL_DutyCycleHandle handle = 0;
+};
+
+struct DIOHandle {
+ public:
+  DIOHandle() {}
+  DIOHandle(const DIOHandle&) = delete;
+  DIOHandle operator=(const DIOHandle&) = delete;
+
+  DIOHandle(DIOHandle&&) = default;
+  DIOHandle& operator=(DIOHandle&&) = default;
+
+  DIOHandle(int32_t port, HAL_Bool input, int32_t* status) {
+    handle = HAL_InitializeDIOPort(HAL_GetPort(port), input, nullptr, status);
+  }
+
+  ~DIOHandle() { HAL_FreeDIOPort(handle); }
+
+  operator HAL_DigitalHandle() const { return handle; }
+
+ private:
+  HAL_DigitalHandle handle = 0;
+};
+
+struct PWMHandle {
+ public:
+  PWMHandle() {}
+  PWMHandle(const PWMHandle&) = delete;
+  PWMHandle operator=(const PWMHandle&) = delete;
+
+  PWMHandle(PWMHandle&&) = default;
+  PWMHandle& operator=(PWMHandle&&) = default;
+
+  PWMHandle(int32_t port, int32_t* status) {
+    handle = HAL_InitializePWMPort(HAL_GetPort(port), nullptr, status);
+  }
+
+  ~PWMHandle() {
+    int32_t status = 0;
+    HAL_FreePWMPort(handle, &status);
+  }
+
+  operator HAL_DigitalHandle() const { return handle; }
+
+ private:
+  HAL_DigitalHandle handle = 0;
+};
+
+struct RelayHandle {
+ public:
+  RelayHandle(int32_t port, HAL_Bool fwd, int32_t* status) {
+    handle = HAL_InitializeRelayPort(HAL_GetPort(port), fwd, nullptr, status);
+  }
+  RelayHandle(const RelayHandle&) = delete;
+  RelayHandle operator=(const RelayHandle&) = delete;
+
+  RelayHandle(RelayHandle&&) = default;
+  RelayHandle& operator=(RelayHandle&&) = default;
+
+  ~RelayHandle() { HAL_FreeRelayPort(handle); }
+
+  operator HAL_RelayHandle() const { return handle; }
+
+ private:
+  HAL_RelayHandle handle = 0;
+};
+
+#define ASSERT_LAST_ERROR_STATUS(status, x)                          \
+  do {                                                               \
+    ASSERT_EQ(status, HAL_USE_LAST_ERROR);                           \
+    const char* lastErrorMessageInMacro = HAL_GetLastError(&status); \
+    ASSERT_EQ(status, x);                                            \
+  } while (0)
+
+}  // namespace hlt

cscore/.styleguide

@@ -31,6 +31,7 @@ repoRootNameOverride {
 }
 
 includeOtherLibs {
+  ^fmt/
   ^opencv2/
   ^support/
   ^tcpsockets/

cscore/CMakeLists.txt

@@ -87,11 +87,11 @@ if (WITH_JAVA)
         set(OPENCV_JAVA_INSTALL_DIR ${OpenCV_INSTALL_PATH}/share/OpenCV/java/)
     endif()
 
-    find_file(OPENCV_JAR_FILE NAMES opencv-${OpenCV_VERSION_MAJOR}${OpenCV_VERSION_MINOR}${OpenCV_VERSION_PATCH}.jar PATHS ${OPENCV_JAVA_INSTALL_DIR} ${OpenCV_INSTALL_PATH}/bin NO_DEFAULT_PATH)
+    find_file(OPENCV_JAR_FILE NAMES opencv-${OpenCV_VERSION_MAJOR}${OpenCV_VERSION_MINOR}${OpenCV_VERSION_PATCH}.jar PATHS ${OPENCV_JAVA_INSTALL_DIR} ${OpenCV_INSTALL_PATH}/bin ${OpenCV_INSTALL_PATH}/share/java NO_DEFAULT_PATH)
     find_file(OPENCV_JNI_FILE NAMES libopencv_java${OpenCV_VERSION_MAJOR}${OpenCV_VERSION_MINOR}${OpenCV_VERSION_PATCH}.so
                                     libopencv_java${OpenCV_VERSION_MAJOR}${OpenCV_VERSION_MINOR}${OpenCV_VERSION_PATCH}.dylib
                                     opencv_java${OpenCV_VERSION_MAJOR}${OpenCV_VERSION_MINOR}${OpenCV_VERSION_PATCH}.dll
-                                    PATHS ${OPENCV_JAVA_INSTALL_DIR} ${OpenCV_INSTALL_PATH}/bin ${OpenCV_INSTALL_PATH}/bin/Release ${OpenCV_INSTALL_PATH}/bin/Debug ${OpenCV_INSTALL_PATH}/lib NO_DEFAULT_PATH)
+                                    PATHS ${OPENCV_JAVA_INSTALL_DIR} ${OpenCV_INSTALL_PATH}/bin ${OpenCV_INSTALL_PATH}/bin/Release ${OpenCV_INSTALL_PATH}/bin/Debug ${OpenCV_INSTALL_PATH}/lib ${OpenCV_INSTALL_PATH}/lib/jni NO_DEFAULT_PATH)
 
     file(GLOB
         cscore_jni_src src/main/native/cpp/jni/CameraServerJNI.cpp)

cscore/examples/enum_usb/enum_usb.cpp

@@ -2,83 +2,77 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-#include <wpi/SmallString.h>
-#include <wpi/raw_ostream.h>
+#include <cstdio>
+
+#include <fmt/format.h>
 
 #include "cscore.h"
 
 int main() {
   CS_Status status = 0;
-  wpi::SmallString<64> buf;
 
   for (const auto& caminfo : cs::EnumerateUsbCameras(&status)) {
-    wpi::outs() << caminfo.dev << ": " << caminfo.path << " (" << caminfo.name
-                << ")\n";
+    fmt::print("{}: {} ({})\n", caminfo.dev, caminfo.path, caminfo.name);
     if (!caminfo.otherPaths.empty()) {
-      wpi::outs() << "Other device paths:\n";
+      std::puts("Other device paths:");
       for (auto&& path : caminfo.otherPaths) {
-        wpi::outs() << "  " << path << '\n';
+        fmt::print("  {}\n", path);
       }
     }
 
     cs::UsbCamera camera{"usbcam", caminfo.dev};
 
-    wpi::outs() << "Properties:\n";
+    std::puts("Properties:");
     for (const auto& prop : camera.EnumerateProperties()) {
-      wpi::outs() << "  " << prop.GetName();
+      fmt::print("  {}", prop.GetName());
       switch (prop.GetKind()) {
         case cs::VideoProperty::kBoolean:
-          wpi::outs() << " (bool): "
-                      << "value=" << prop.Get()
-                      << " default=" << prop.GetDefault();
+          fmt::print(" (bool): value={} default={}", prop.Get(),
+                     prop.GetDefault());
           break;
         case cs::VideoProperty::kInteger:
-          wpi::outs() << " (int): "
-                      << "value=" << prop.Get() << " min=" << prop.GetMin()
-                      << " max=" << prop.GetMax() << " step=" << prop.GetStep()
-                      << " default=" << prop.GetDefault();
+          fmt::print(" (int): value={} min={} max={} step={} default={}",
+                     prop.Get(), prop.GetMin(), prop.GetMax(), prop.GetStep(),
+                     prop.GetDefault());
           break;
         case cs::VideoProperty::kString:
-          wpi::outs() << " (string): " << prop.GetString(buf);
+          fmt::print(" (string): {}", prop.GetString());
           break;
         case cs::VideoProperty::kEnum: {
-          wpi::outs() << " (enum): "
-                      << "value=" << prop.Get();
+          fmt::print(" (enum): value={}", prop.Get());
           auto choices = prop.GetChoices();
           for (size_t i = 0; i < choices.size(); ++i) {
-            if (choices[i].empty()) {
-              continue;
+            if (!choices[i].empty()) {
+              fmt::print("\n    {}: {}", i, choices[i]);
             }
-            wpi::outs() << "\n    " << i << ": " << choices[i];
           }
           break;
         }
         default:
           break;
       }
-      wpi::outs() << '\n';
+      std::fputc('\n', stdout);
     }
 
-    wpi::outs() << "Video Modes:\n";
+    std::puts("Video Modes:");
     for (const auto& mode : camera.EnumerateVideoModes()) {
-      wpi::outs() << "  PixelFormat:";
+      const char* pixelFormat;
       switch (mode.pixelFormat) {
         case cs::VideoMode::kMJPEG:
-          wpi::outs() << "MJPEG";
+          pixelFormat = "MJPEG";
           break;
         case cs::VideoMode::kYUYV:
-          wpi::outs() << "YUYV";
+          pixelFormat = "YUYV";
           break;
         case cs::VideoMode::kRGB565:
-          wpi::outs() << "RGB565";
+          pixelFormat = "RGB565";
           break;
         default:
-          wpi::outs() << "Unknown";
+          pixelFormat = "Unknown";
           break;
       }
-      wpi::outs() << " Width:" << mode.width;
-      wpi::outs() << " Height:" << mode.height;
-      wpi::outs() << " FPS:" << mode.fps << '\n';
+      fmt::print("  PixelFormat:{} Width:{} Height:{} FPS:{}\n", pixelFormat,
+                 mode.width, mode.height, mode.fps);
     }
   }
 }

cscore/examples/settings/settings.cpp

@@ -3,23 +3,27 @@
 // the WPILib BSD license file in the root directory of this project.
 
 #include <chrono>
+#include <cstdio>
 #include <thread>
 
-#include <wpi/SmallString.h>
-#include <wpi/raw_ostream.h>
+#include <fmt/format.h>
+#include <wpi/StringExtras.h>
 
 #include "cscore.h"
 
 int main(int argc, char** argv) {
   if (argc < 2) {
-    wpi::errs() << "Usage: settings camera [prop val] ... -- [prop val]...\n";
-    wpi::errs() << "  Example: settings 1 brightness 30 raw_contrast 10\n";
+    std::fputs("Usage: settings camera [prop val] ... -- [prop val]...\n",
+               stderr);
+    std::fputs("  Example: settings 1 brightness 30 raw_contrast 10\n", stderr);
     return 1;
   }
 
   int id;
-  if (wpi::StringRef{argv[1]}.getAsInteger(10, id)) {
-    wpi::errs() << "Expected number for camera\n";
+  if (auto v = wpi::parse_integer<int>(argv[1], 10)) {
+    id = v.value();
+  } else {
+    std::fputs("Expected number for camera\n", stderr);
     return 2;
   }
 
@@ -27,22 +31,21 @@ int main(int argc, char** argv) {
 
   // Set prior to connect
   int arg = 2;
-  wpi::StringRef propName;
-  for (; arg < argc && wpi::StringRef{argv[arg]} != "--"; ++arg) {
+  std::string_view propName;
+  for (; arg < argc && std::string_view{argv[arg]} != "--"; ++arg) {
     if (propName.empty()) {
       propName = argv[arg];
     } else {
-      wpi::StringRef propVal{argv[arg]};
-      int intVal;
-      if (propVal.getAsInteger(10, intVal)) {
-        camera.GetProperty(propName).SetString(propVal);
+      std::string_view propVal{argv[arg]};
+      if (auto v = wpi::parse_integer<int>(propVal, 10)) {
+        camera.GetProperty(propName).Set(v.value());
       } else {
-        camera.GetProperty(propName).Set(intVal);
+        camera.GetProperty(propName).SetString(propVal);
       }
-      propName = wpi::StringRef{};
+      propName = {};
     }
   }
-  if (arg < argc && wpi::StringRef{argv[arg]} == "--") {
+  if (arg < argc && std::string_view{argv[arg]} == "--") {
     ++arg;
   }
 
@@ -52,57 +55,51 @@ int main(int argc, char** argv) {
   }
 
   // Set rest
-  propName = wpi::StringRef{};
+  propName = {};
   for (; arg < argc; ++arg) {
     if (propName.empty()) {
       propName = argv[arg];
     } else {
-      wpi::StringRef propVal{argv[arg]};
-      int intVal;
-      if (propVal.getAsInteger(10, intVal)) {
-        camera.GetProperty(propName).SetString(propVal);
+      std::string_view propVal{argv[arg]};
+      if (auto v = wpi::parse_integer<int>(propVal, 10)) {
+        camera.GetProperty(propName).Set(v.value());
       } else {
-        camera.GetProperty(propName).Set(intVal);
+        camera.GetProperty(propName).SetString(propVal);
       }
-      propName = wpi::StringRef{};
+      propName = {};
     }
   }
 
   // Print settings
-  wpi::SmallString<64> buf;
-  wpi::outs() << "Properties:\n";
+  std::puts("Properties:");
   for (const auto& prop : camera.EnumerateProperties()) {
-    wpi::outs() << "  " << prop.GetName();
+    fmt::print("  {}", prop.GetName());
     switch (prop.GetKind()) {
       case cs::VideoProperty::kBoolean:
-        wpi::outs() << " (bool): "
-                    << "value=" << prop.Get()
-                    << " default=" << prop.GetDefault();
+        fmt::print(" (bool): value={} default={}", prop.Get(),
+                   prop.GetDefault());
         break;
       case cs::VideoProperty::kInteger:
-        wpi::outs() << " (int): "
-                    << "value=" << prop.Get() << " min=" << prop.GetMin()
-                    << " max=" << prop.GetMax() << " step=" << prop.GetStep()
-                    << " default=" << prop.GetDefault();
+        fmt::print(" (int): value={} min={} max={} step={} default={}",
+                   prop.Get(), prop.GetMin(), prop.GetMax(), prop.GetStep(),
+                   prop.GetDefault());
         break;
       case cs::VideoProperty::kString:
-        wpi::outs() << " (string): " << prop.GetString(buf);
+        fmt::print(" (string): {}", prop.GetString());
         break;
       case cs::VideoProperty::kEnum: {
-        wpi::outs() << " (enum): "
-                    << "value=" << prop.Get();
+        fmt::print(" (enum): value={}", prop.Get());
         auto choices = prop.GetChoices();
         for (size_t i = 0; i < choices.size(); ++i) {
-          if (choices[i].empty()) {
-            continue;
+          if (!choices[i].empty()) {
+            fmt::print("\n    {}: {}", i, choices[i]);
           }
-          wpi::outs() << "\n    " << i << ": " << choices[i];
         }
         break;
       }
       default:
         break;
     }
-    wpi::outs() << '\n';
+    std::fputc('\n', stdout);
   }
 }

cscore/examples/usbstream/usbstream.cpp

@@ -4,15 +4,15 @@
 
 #include <cstdio>
 
-#include <wpi/raw_ostream.h>
+#include <fmt/format.h>
 
 #include "cscore.h"
 
 int main() {
-  wpi::outs() << "hostname: " << cs::GetHostname() << '\n';
-  wpi::outs() << "IPv4 network addresses:\n";
+  fmt::print("hostname: {}\n", cs::GetHostname());
+  std::puts("IPv4 network addresses:");
   for (const auto& addr : cs::GetNetworkInterfaces()) {
-    wpi::outs() << "  " << addr << '\n';
+    fmt::print("  {}\n", addr);
   }
   cs::UsbCamera camera{"usbcam", 0};
   camera.SetVideoMode(cs::VideoMode::kMJPEG, 320, 240, 30);
@@ -22,9 +22,8 @@ int main() {
   CS_Status status = 0;
   cs::AddListener(
       [&](const cs::RawEvent& event) {
-        wpi::outs() << "FPS=" << camera.GetActualFPS()
-                    << " MBPS=" << (camera.GetActualDataRate() / 1000000.0)
-                    << '\n';
+        fmt::print("FPS={} MBPS={}\n", camera.GetActualFPS(),
+                   (camera.GetActualDataRate() / 1000000.0));
       },
       cs::RawEvent::kTelemetryUpdated, false, &status);
   cs::SetTelemetryPeriod(1.0);

cscore/examples/usbviewer/usbviewer.cpp

@@ -6,12 +6,13 @@
 #include <thread>
 #include <vector>
 
+#include <fmt/format.h>
+
 #define IMGUI_DEFINE_MATH_OPERATORS
 #include <imgui.h>
 #include <imgui_internal.h>
 #include <opencv2/core/core.hpp>
 #include <opencv2/imgproc.hpp>
-#include <wpi/raw_ostream.h>
 #include <wpi/spinlock.h>
 #include <wpigui.h>
 
@@ -38,7 +39,7 @@ int main() {
       // get frame from camera
       uint64_t time = cvsink.GrabFrame(frame);
       if (time == 0) {
-        wpi::outs() << "error: " << cvsink.GetError() << '\n';
+        fmt::print("error: {}\n", cvsink.GetError());
         continue;
       }
 

cscore/src/dev/java/edu/wpi/first/cscore/DevMain.java

@@ -2,9 +2,9 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
-import edu.wpi.first.wpiutil.RuntimeDetector;
+import edu.wpi.first.util.RuntimeDetector;
 
 public final class DevMain {
   /** Main method. */

cscore/src/main/java/edu/wpi/cscore/VideoListener.java

@@ -1,39 +0,0 @@
-// Copyright (c) FIRST and other WPILib contributors.
-// Open Source Software; you can modify and/or share it under the terms of
-// the WPILib BSD license file in the root directory of this project.
-
-package edu.wpi.cscore;
-
-import java.util.function.Consumer;
-
-/**
- * An event listener. This calls back to a desigated callback function when an event matching the
- * specified mask is generated by the library.
- */
-public class VideoListener implements AutoCloseable {
-  /**
-   * Create an event listener.
-   *
-   * @param listener Listener function
-   * @param eventMask Bitmask of VideoEvent.Type values
-   * @param immediateNotify Whether callback should be immediately called with a representative set
-   *     of events for the current library state.
-   */
-  public VideoListener(Consumer<VideoEvent> listener, int eventMask, boolean immediateNotify) {
-    m_handle = CameraServerJNI.addListener(listener, eventMask, immediateNotify);
-  }
-
-  @Override
-  public synchronized void close() {
-    if (m_handle != 0) {
-      CameraServerJNI.removeListener(m_handle);
-    }
-    m_handle = 0;
-  }
-
-  public boolean isValid() {
-    return m_handle != 0;
-  }
-
-  private int m_handle;
-}

cscore/src/main/java/edu/wpi/first/cscore/AxisCamera.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 /** A source that represents an Axis IP camera. */
 public class AxisCamera extends HttpCamera {

cscore/src/main/java/edu/wpi/first/cscore/CameraServerCvJNI.java

@@ -2,9 +2,9 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
-import edu.wpi.first.wpiutil.RuntimeLoader;
+import edu.wpi.first.util.RuntimeLoader;
 import java.io.IOException;
 import java.util.concurrent.atomic.AtomicBoolean;
 import org.opencv.core.Core;
@@ -42,7 +42,11 @@ public class CameraServerCvJNI {
     }
   }
 
-  /** Force load the library. */
+  /**
+   * Force load the library.
+   *
+   * @throws IOException if library load failed
+   */
   public static synchronized void forceLoad() throws IOException {
     if (libraryLoaded) {
       return;

cscore/src/main/java/edu/wpi/first/cscore/CameraServerJNI.java

@@ -2,10 +2,10 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
-import edu.wpi.cscore.raw.RawFrame;
-import edu.wpi.first.wpiutil.RuntimeLoader;
+import edu.wpi.first.cscore.raw.RawFrame;
+import edu.wpi.first.util.RuntimeLoader;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -43,7 +43,11 @@ public class CameraServerJNI {
     }
   }
 
-  /** Force load the library. */
+  /**
+   * Force load the library.
+   *
+   * @throws IOException if library load failed
+   */
   public static synchronized void forceLoad() throws IOException {
     if (libraryLoaded) {
       return;
@@ -313,6 +317,19 @@ public class CameraServerJNI {
 
   public static native void removeListener(int handle);
 
+  public static native int createListenerPoller();
+
+  public static native void destroyListenerPoller(int poller);
+
+  public static native int addPolledListener(int poller, int eventMask, boolean immediateNotify);
+
+  public static native VideoEvent[] pollListener(int poller) throws InterruptedException;
+
+  public static native VideoEvent[] pollListenerTimeout(int poller, double timeout)
+      throws InterruptedException;
+
+  public static native void cancelPollListener(int poller);
+
   //
   // Telemetry Functions
   //

cscore/src/main/java/edu/wpi/first/cscore/CvSink.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 import org.opencv.core.Mat;
 
@@ -38,6 +38,7 @@ public class CvSink extends ImageSink {
    * Wait for the next frame and get the image. Times out (returning 0) after 0.225 seconds. The
    * provided image will have three 3-bit channels stored in BGR order.
    *
+   * @param image Where to store the image.
    * @return Frame time, or 0 on error (call GetError() to obtain the error message)
    */
   public long grabFrame(Mat image) {
@@ -48,6 +49,8 @@ public class CvSink extends ImageSink {
    * Wait for the next frame and get the image. Times out (returning 0) after timeout seconds. The
    * provided image will have three 3-bit channels stored in BGR order.
    *
+   * @param image Where to store the image.
+   * @param timeout Retrieval timeout in seconds.
    * @return Frame time, or 0 on error (call GetError() to obtain the error message); the frame time
    *     is in 1 us increments.
    */
@@ -59,6 +62,7 @@ public class CvSink extends ImageSink {
    * Wait for the next frame and get the image. May block forever. The provided image will have
    * three 3-bit channels stored in BGR order.
    *
+   * @param image Where to store the image.
    * @return Frame time, or 0 on error (call GetError() to obtain the error message); the frame time
    *     is in 1 us increments.
    */

cscore/src/main/java/edu/wpi/first/cscore/CvSource.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 import org.opencv.core.Mat;
 

cscore/src/main/java/edu/wpi/first/cscore/HttpCamera.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 /** A source that represents a MJPEG-over-HTTP (IP) camera. */
 public class HttpCamera extends VideoCamera {
@@ -88,17 +88,27 @@ public class HttpCamera extends VideoCamera {
    * Get the kind of HTTP camera.
    *
    * <p>Autodetection can result in returning a different value than the camera was created with.
+   *
+   * @return The kind of HTTP camera.
    */
   public HttpCameraKind getHttpCameraKind() {
     return getHttpCameraKindFromInt(CameraServerJNI.getHttpCameraKind(m_handle));
   }
 
-  /** Change the URLs used to connect to the camera. */
+  /**
+   * Change the URLs used to connect to the camera.
+   *
+   * @param urls Array of Camera URLs
+   */
   public void setUrls(String[] urls) {
     CameraServerJNI.setHttpCameraUrls(m_handle, urls);
   }
 
-  /** Get the URLs used to connect to the camera. */
+  /**
+   * Get the URLs used to connect to the camera.
+   *
+   * @return Array of camera URLs.
+   */
   public String[] getUrls() {
     return CameraServerJNI.getHttpCameraUrls(m_handle);
   }

cscore/src/main/java/edu/wpi/first/cscore/ImageSink.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 public abstract class ImageSink extends VideoSink {
   protected ImageSink(int handle) {
@@ -18,7 +18,11 @@ public abstract class ImageSink extends VideoSink {
     CameraServerJNI.setSinkDescription(m_handle, description);
   }
 
-  /** Get error string. Call this if WaitForFrame() returns 0 to determine what the error is. */
+  /**
+   * Get error string. Call this if WaitForFrame() returns 0 to determine what the error is.
+   *
+   * @return Error string.
+   */
   public String getError() {
     return CameraServerJNI.getSinkError(m_handle);
   }
@@ -27,6 +31,8 @@ public abstract class ImageSink extends VideoSink {
    * Enable or disable getting new frames. Disabling will cause processFrame (for callback-based
    * CvSinks) to not be called and WaitForFrame() to not return. This can be used to save processor
    * resources when frames are not needed.
+   *
+   * @param enabled Enable to get new frames.
    */
   public void setEnabled(boolean enabled) {
     CameraServerJNI.setSinkEnabled(m_handle, enabled);

cscore/src/main/java/edu/wpi/first/cscore/ImageSource.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 public abstract class ImageSource extends VideoSource {
   protected ImageSource(int handle) {
@@ -12,6 +12,8 @@ public abstract class ImageSource extends VideoSource {
   /**
    * Signal sinks that an error has occurred. This should be called instead of NotifyFrame when an
    * error occurs.
+   *
+   * @param msg Error message.
    */
   public void notifyError(String msg) {
     CameraServerJNI.notifySourceError(m_handle, msg);

cscore/src/main/java/edu/wpi/first/cscore/MjpegServer.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 /** A sink that acts as a MJPEG-over-HTTP network server. */
 public class MjpegServer extends VideoSink {
@@ -27,12 +27,20 @@ public class MjpegServer extends VideoSink {
     this(name, "", port);
   }
 
-  /** Get the listen address of the server. */
+  /**
+   * Get the listen address of the server.
+   *
+   * @return The listen address.
+   */
   public String getListenAddress() {
     return CameraServerJNI.getMjpegServerListenAddress(m_handle);
   }
 
-  /** Get the port number of the server. */
+  /**
+   * Get the port number of the server.
+   *
+   * @return The port number.
+   */
   public int getPort() {
     return CameraServerJNI.getMjpegServerPort(m_handle);
   }

cscore/src/main/java/edu/wpi/first/cscore/UsbCamera.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 /** A source that represents a USB camera. */
 public class UsbCamera extends VideoCamera {
@@ -35,17 +35,29 @@ public class UsbCamera extends VideoCamera {
     return CameraServerJNI.enumerateUsbCameras();
   }
 
-  /** Change the path to the device. */
+  /**
+   * Change the path to the device.
+   *
+   * @param path New device path.
+   */
   void setPath(String path) {
     CameraServerJNI.setUsbCameraPath(m_handle, path);
   }
 
-  /** Get the path to the device. */
+  /**
+   * Get the path to the device.
+   *
+   * @return The device path.
+   */
   public String getPath() {
     return CameraServerJNI.getUsbCameraPath(m_handle);
   }
 
-  /** Get the full camera information for the device. */
+  /**
+   * Get the full camera information for the device.
+   *
+   * @return The camera information.
+   */
   public UsbCameraInfo getInfo() {
     return CameraServerJNI.getUsbCameraInfo(m_handle);
   }

cscore/src/main/java/edu/wpi/first/cscore/UsbCameraInfo.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 /** USB camera information. */
 public class UsbCameraInfo {

cscore/src/main/java/edu/wpi/first/cscore/VideoCamera.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 /** A source that represents a video camera. */
 public class VideoCamera extends VideoSource {
@@ -18,12 +18,20 @@ public class VideoCamera extends VideoSource {
     super(handle);
   }
 
-  /** Set the brightness, as a percentage (0-100). */
+  /**
+   * Set the brightness, as a percentage (0-100).
+   *
+   * @param brightness Brightness as a percentage (0-100).
+   */
   public synchronized void setBrightness(int brightness) {
     CameraServerJNI.setCameraBrightness(m_handle, brightness);
   }
 
-  /** Get the brightness, as a percentage (0-100). */
+  /**
+   * Get the brightness, as a percentage (0-100).
+   *
+   * @return The brightness as a percentage (0-100).
+   */
   public synchronized int getBrightness() {
     return CameraServerJNI.getCameraBrightness(m_handle);
   }
@@ -38,7 +46,11 @@ public class VideoCamera extends VideoSource {
     CameraServerJNI.setCameraWhiteBalanceHoldCurrent(m_handle);
   }
 
-  /** Set the white balance to manual, with specified color temperature. */
+  /**
+   * Set the white balance to manual, with specified color temperature.
+   *
+   * @param value The specified color temperature.
+   */
   public synchronized void setWhiteBalanceManual(int value) {
     CameraServerJNI.setCameraWhiteBalanceManual(m_handle, value);
   }
@@ -53,7 +65,11 @@ public class VideoCamera extends VideoSource {
     CameraServerJNI.setCameraExposureHoldCurrent(m_handle);
   }
 
-  /** Set the exposure to manual, as a percentage (0-100). */
+  /**
+   * Set the exposure to manual, as a percentage (0-100).
+   *
+   * @param value The exposure as a percentage (0-100).
+   */
   public synchronized void setExposureManual(int value) {
     CameraServerJNI.setCameraExposureManual(m_handle, value);
   }

cscore/src/main/java/edu/wpi/first/cscore/VideoEvent.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 /** Video event. */
 public class VideoEvent {
@@ -26,7 +26,8 @@ public class VideoEvent {
     kTelemetryUpdated(0x8000),
     kSinkPropertyCreated(0x10000),
     kSinkPropertyValueUpdated(0x20000),
-    kSinkPropertyChoicesUpdated(0x40000);
+    kSinkPropertyChoicesUpdated(0x40000),
+    kUsbCamerasChanged(0x80000);
 
     private final int value;
 
@@ -45,7 +46,6 @@ public class VideoEvent {
    * @param kind The numerical representation of kind
    * @return The kind
    */
-  @SuppressWarnings("PMD.CyclomaticComplexity")
   public static Kind getKindFromInt(int kind) {
     switch (kind) {
       case 0x0001:
@@ -84,12 +84,13 @@ public class VideoEvent {
         return Kind.kSinkPropertyValueUpdated;
       case 0x40000:
         return Kind.kSinkPropertyChoicesUpdated;
+      case 0x80000:
+        return Kind.kUsbCamerasChanged;
       default:
         return Kind.kUnknown;
     }
   }
 
-  @SuppressWarnings("PMD.ExcessiveParameterList")
   VideoEvent(
       int kind,
       int source,
@@ -102,7 +103,8 @@ public class VideoEvent {
       int property,
       int propertyKind,
       int value,
-      String valueStr) {
+      String valueStr,
+      int listener) {
     this.kind = getKindFromInt(kind);
     this.sourceHandle = source;
     this.sinkHandle = sink;
@@ -112,6 +114,7 @@ public class VideoEvent {
     this.propertyKind = VideoProperty.getKindFromInt(propertyKind);
     this.value = value;
     this.valueStr = valueStr;
+    this.listener = listener;
   }
 
   @SuppressWarnings("MemberName")
@@ -145,6 +148,10 @@ public class VideoEvent {
   @SuppressWarnings("MemberName")
   public String valueStr;
 
+  // Listener that was triggered
+  @SuppressWarnings("MemberName")
+  public int listener;
+
   public VideoSource getSource() {
     return new VideoSource(CameraServerJNI.copySource(sourceHandle));
   }

cscore/src/main/java/edu/wpi/first/cscore/VideoException.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 /** An exception raised by the camera server. */
 public class VideoException extends RuntimeException {

cscore/src/main/java/edu/wpi/first/cscore/VideoListener.java

@@ -0,0 +1,126 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+package edu.wpi.first.cscore;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Consumer;
+
+/**
+ * An event listener. This calls back to a desigated callback function when an event matching the
+ * specified mask is generated by the library.
+ */
+public class VideoListener implements AutoCloseable {
+  /**
+   * Create an event listener.
+   *
+   * @param listener Listener function
+   * @param eventMask Bitmask of VideoEvent.Type values
+   * @param immediateNotify Whether callback should be immediately called with a representative set
+   *     of events for the current library state.
+   */
+  public VideoListener(Consumer<VideoEvent> listener, int eventMask, boolean immediateNotify) {
+    s_lock.lock();
+    try {
+      if (s_poller == 0) {
+        s_poller = CameraServerJNI.createListenerPoller();
+        startThread();
+      }
+      m_handle = CameraServerJNI.addPolledListener(s_poller, eventMask, immediateNotify);
+      s_listeners.put(m_handle, listener);
+    } finally {
+      s_lock.unlock();
+    }
+  }
+
+  @Override
+  public synchronized void close() {
+    if (m_handle != 0) {
+      s_lock.lock();
+      try {
+        s_listeners.remove(m_handle);
+      } finally {
+        s_lock.unlock();
+      }
+      CameraServerJNI.removeListener(m_handle);
+      m_handle = 0;
+    }
+  }
+
+  public boolean isValid() {
+    return m_handle != 0;
+  }
+
+  private int m_handle;
+
+  private static final ReentrantLock s_lock = new ReentrantLock();
+  private static final Map<Integer, Consumer<VideoEvent>> s_listeners = new HashMap<>();
+  private static Thread s_thread;
+  private static int s_poller;
+  private static boolean s_waitQueue;
+  private static final Condition s_waitQueueCond = s_lock.newCondition();
+
+  @SuppressWarnings("PMD.AvoidCatchingThrowable")
+  private static void startThread() {
+    s_thread =
+        new Thread(
+            () -> {
+              boolean wasInterrupted = false;
+              while (!Thread.interrupted()) {
+                VideoEvent[] events;
+                try {
+                  events = CameraServerJNI.pollListener(s_poller);
+                } catch (InterruptedException ex) {
+                  s_lock.lock();
+                  try {
+                    if (s_waitQueue) {
+                      s_waitQueue = false;
+                      s_waitQueueCond.signalAll();
+                      continue;
+                    }
+                  } finally {
+                    s_lock.unlock();
+                  }
+                  Thread.currentThread().interrupt();
+                  // don't try to destroy poller, as its handle is likely no longer valid
+                  wasInterrupted = true;
+                  break;
+                }
+                for (VideoEvent event : events) {
+                  Consumer<VideoEvent> listener;
+                  s_lock.lock();
+                  try {
+                    listener = s_listeners.get(event.listener);
+                  } finally {
+                    s_lock.unlock();
+                  }
+                  if (listener != null) {
+                    try {
+                      listener.accept(event);
+                    } catch (Throwable throwable) {
+                      System.err.println(
+                          "Unhandled exception during listener callback: " + throwable.toString());
+                      throwable.printStackTrace();
+                    }
+                  }
+                }
+              }
+              s_lock.lock();
+              try {
+                if (!wasInterrupted) {
+                  CameraServerJNI.destroyListenerPoller(s_poller);
+                }
+                s_poller = 0;
+              } finally {
+                s_lock.unlock();
+              }
+            },
+            "VideoListener");
+    s_thread.setDaemon(true);
+    s_thread.start();
+  }
+}

cscore/src/main/java/edu/wpi/first/cscore/VideoMode.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 /** Video mode. */
 public class VideoMode {
@@ -31,7 +31,14 @@ public class VideoMode {
     return m_pixelFormatValues[pixelFormat];
   }
 
-  /** Create a new video mode. */
+  /**
+   * Create a new video mode.
+   *
+   * @param pixelFormat The pixel format enum as an integer.
+   * @param width The image width in pixels.
+   * @param height The image height in pixels.
+   * @param fps The camera's frames per second.
+   */
   public VideoMode(int pixelFormat, int width, int height, int fps) {
     this.pixelFormat = getPixelFormatFromInt(pixelFormat);
     this.width = width;
@@ -39,7 +46,14 @@ public class VideoMode {
     this.fps = fps;
   }
 
-  /** Create a new video mode. */
+  /**
+   * Create a new video mode.
+   *
+   * @param pixelFormat The pixel format.
+   * @param width The image width in pixels.
+   * @param height The image height in pixels.
+   * @param fps The camera's frames per second.
+   */
   public VideoMode(PixelFormat pixelFormat, int width, int height, int fps) {
     this.pixelFormat = pixelFormat;
     this.width = width;

cscore/src/main/java/edu/wpi/first/cscore/VideoProperty.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 /** A source or sink property. */
 public class VideoProperty {

cscore/src/main/java/edu/wpi/first/cscore/VideoSink.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 /**
  * A source for video that provides a sequence of frames. Each frame may consist of multiple images
@@ -83,7 +83,11 @@ public class VideoSink implements AutoCloseable {
     return m_handle;
   }
 
-  /** Get the kind of the sink. */
+  /**
+   * Get the kind of the sink.
+   *
+   * @return The kind of the sink.
+   */
   public Kind getKind() {
     return getKindFromInt(CameraServerJNI.getSinkKind(m_handle));
   }
@@ -91,12 +95,18 @@ public class VideoSink implements AutoCloseable {
   /**
    * Get the name of the sink. The name is an arbitrary identifier provided when the sink is
    * created, and should be unique.
+   *
+   * @return The name of the sink.
    */
   public String getName() {
     return CameraServerJNI.getSinkName(m_handle);
   }
 
-  /** Get the sink description. This is sink-kind specific. */
+  /**
+   * Get the sink description. This is sink-kind specific.
+   *
+   * @return The sink description.
+   */
   public String getDescription() {
     return CameraServerJNI.getSinkDescription(m_handle);
   }
@@ -111,8 +121,11 @@ public class VideoSink implements AutoCloseable {
     return new VideoProperty(CameraServerJNI.getSinkProperty(m_handle, name));
   }
 
-  /** Enumerate all properties of this sink. */
-  @SuppressWarnings("PMD.AvoidInstantiatingObjectsInLoops")
+  /**
+   * Enumerate all properties of this sink.
+   *
+   * @return List of properties.
+   */
   public VideoProperty[] enumerateProperties() {
     int[] handles = CameraServerJNI.enumerateSinkProperties(m_handle);
     VideoProperty[] rv = new VideoProperty[handles.length];
@@ -195,7 +208,6 @@ public class VideoSink implements AutoCloseable {
    *
    * @return Vector of sinks.
    */
-  @SuppressWarnings("PMD.AvoidInstantiatingObjectsInLoops")
   public static VideoSink[] enumerateSinks() {
     int[] handles = CameraServerJNI.enumerateSinks();
     VideoSink[] rv = new VideoSink[handles.length];

cscore/src/main/java/edu/wpi/first/cscore/VideoSource.java

@@ -2,7 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore;
+package edu.wpi.first.cscore;
 
 /**
  * A source for video that provides a sequence of frames. Each frame may consist of multiple images
@@ -113,7 +113,11 @@ public class VideoSource implements AutoCloseable {
     return m_handle;
   }
 
-  /** Get the kind of the source. */
+  /**
+   * Get the kind of the source.
+   *
+   * @return The kind of the source.
+   */
   public Kind getKind() {
     return getKindFromInt(CameraServerJNI.getSourceKind(m_handle));
   }
@@ -121,12 +125,18 @@ public class VideoSource implements AutoCloseable {
   /**
    * Get the name of the source. The name is an arbitrary identifier provided when the source is
    * created, and should be unique.
+   *
+   * @return The name of the source.
    */
   public String getName() {
     return CameraServerJNI.getSourceName(m_handle);
   }
 
-  /** Get the source description. This is source-kind specific. */
+  /**
+   * Get the source description. This is source-kind specific.
+   *
+   * @return The source description.
+   */
   public String getDescription() {
     return CameraServerJNI.getSourceDescription(m_handle);
   }
@@ -153,7 +163,11 @@ public class VideoSource implements AutoCloseable {
     CameraServerJNI.setSourceConnectionStrategy(m_handle, strategy.getValue());
   }
 
-  /** Returns if the source currently connected to whatever is providing the images. */
+  /**
+   * Returns true if the source currently connected to whatever is providing the images.
+   *
+   * @return True if the source currently connected to whatever is providing the images.
+   */
   public boolean isConnected() {
     return CameraServerJNI.isSourceConnected(m_handle);
   }
@@ -178,8 +192,11 @@ public class VideoSource implements AutoCloseable {
     return new VideoProperty(CameraServerJNI.getSourceProperty(m_handle, name));
   }
 
-  /** Enumerate all properties of this source. */
-  @SuppressWarnings("PMD.AvoidInstantiatingObjectsInLoops")
+  /**
+   * Enumerate all properties of this source.
+   *
+   * @return Array of video properties.
+   */
   public VideoProperty[] enumerateProperties() {
     int[] handles = CameraServerJNI.enumerateSourceProperties(m_handle);
     VideoProperty[] rv = new VideoProperty[handles.length];
@@ -189,7 +206,11 @@ public class VideoSource implements AutoCloseable {
     return rv;
   }
 
-  /** Get the current video mode. */
+  /**
+   * Get the current video mode.
+   *
+   * @return The current video mode.
+   */
   public VideoMode getVideoMode() {
     return CameraServerJNI.getSourceVideoMode(m_handle);
   }
@@ -198,6 +219,7 @@ public class VideoSource implements AutoCloseable {
    * Set the video mode.
    *
    * @param mode Video mode
+   * @return True if set successfully.
    */
   public boolean setVideoMode(VideoMode mode) {
     return CameraServerJNI.setSourceVideoMode(
@@ -313,7 +335,11 @@ public class VideoSource implements AutoCloseable {
         m_handle, CameraServerJNI.TelemetryKind.kSourceBytesReceived);
   }
 
-  /** Enumerate all known video modes for this source. */
+  /**
+   * Enumerate all known video modes for this source.
+   *
+   * @return Vector of video modes.
+   */
   public VideoMode[] enumerateVideoModes() {
     return CameraServerJNI.enumerateSourceVideoModes(m_handle);
   }
@@ -323,7 +349,6 @@ public class VideoSource implements AutoCloseable {
    *
    * @return Vector of sinks.
    */
-  @SuppressWarnings("PMD.AvoidInstantiatingObjectsInLoops")
   public VideoSink[] enumerateSinks() {
     int[] handles = CameraServerJNI.enumerateSourceSinks(m_handle);
     VideoSink[] rv = new VideoSink[handles.length];
@@ -338,7 +363,6 @@ public class VideoSource implements AutoCloseable {
    *
    * @return Vector of sources.
    */
-  @SuppressWarnings("PMD.AvoidInstantiatingObjectsInLoops")
   public static VideoSource[] enumerateSources() {
     int[] handles = CameraServerJNI.enumerateSources();
     VideoSource[] rv = new VideoSource[handles.length];

cscore/src/main/java/edu/wpi/first/cscore/raw/RawFrame.java

@@ -2,9 +2,9 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore.raw;
+package edu.wpi.first.cscore.raw;
 
-import edu.wpi.cscore.CameraServerJNI;
+import edu.wpi.first.cscore.CameraServerJNI;
 import java.nio.ByteBuffer;
 
 /**
@@ -35,7 +35,16 @@ public class RawFrame implements AutoCloseable {
     CameraServerJNI.freeRawFrame(m_framePtr);
   }
 
-  /** Called from JNI to set data in class. */
+  /**
+   * Called from JNI to set data in class.
+   *
+   * @param dataByteBuffer A ByteBuffer pointing to the frame data.
+   * @param dataPtr A long (a char* in native code) pointing to the frame data.
+   * @param totalData The total length of the data stored in the frame.
+   * @param width The width of the frame.
+   * @param height The height of the frame.
+   * @param pixelFormat The PixelFormat of the frame.
+   */
   public void setData(
       ByteBuffer dataByteBuffer,
       long dataPtr,
@@ -51,7 +60,11 @@ public class RawFrame implements AutoCloseable {
     m_pixelFormat = pixelFormat;
   }
 
-  /** Get the pointer to native representation of this frame. */
+  /**
+   * Get the pointer to native representation of this frame.
+   *
+   * @return The pointer to native representation of this frame.
+   */
   public long getFramePtr() {
     return m_framePtr;
   }
@@ -60,6 +73,8 @@ public class RawFrame implements AutoCloseable {
    * Get a ByteBuffer pointing to the frame data. This ByteBuffer is backed by the frame directly.
    * Its lifetime is controlled by the frame. If a new frame gets read, it will overwrite the
    * current one.
+   *
+   * @return A ByteBuffer pointing to the frame data.
    */
   public ByteBuffer getDataByteBuffer() {
     return m_dataByteBuffer;
@@ -69,42 +84,72 @@ public class RawFrame implements AutoCloseable {
    * Get a long (is a char* in native code) pointing to the frame data. This pointer is backed by
    * the frame directly. Its lifetime is controlled by the frame. If a new frame gets read, it will
    * overwrite the current one.
+   *
+   * @return A long pointing to the frame data.
    */
   public long getDataPtr() {
     return m_dataPtr;
   }
 
-  /** Get the total length of the data stored in the frame. */
+  /**
+   * Get the total length of the data stored in the frame.
+   *
+   * @return The total length of the data stored in the frame.
+   */
   public int getTotalData() {
     return m_totalData;
   }
 
-  /** Get the width of the frame. */
+  /**
+   * Get the width of the frame.
+   *
+   * @return The width of the frame.
+   */
   public int getWidth() {
     return m_width;
   }
 
-  /** Set the width of the frame. */
+  /**
+   * Set the width of the frame.
+   *
+   * @param width The width of the frame.
+   */
   public void setWidth(int width) {
     this.m_width = width;
   }
 
-  /** Get the height of the frame. */
+  /**
+   * Get the height of the frame.
+   *
+   * @return The height of the frame.
+   */
   public int getHeight() {
     return m_height;
   }
 
-  /** Set the height of the frame. */
+  /**
+   * Set the height of the frame.
+   *
+   * @param height The height of the frame.
+   */
   public void setHeight(int height) {
     this.m_height = height;
   }
 
-  /** Get the PixelFormat of the frame. */
+  /**
+   * Get the PixelFormat of the frame.
+   *
+   * @return The PixelFormat of the frame.
+   */
   public int getPixelFormat() {
     return m_pixelFormat;
   }
 
-  /** Set the PixelFormat of the frame. */
+  /**
+   * Set the PixelFormat of the frame.
+   *
+   * @param pixelFormat The PixelFormat of the frame.
+   */
   public void setPixelFormat(int pixelFormat) {
     this.m_pixelFormat = pixelFormat;
   }

cscore/src/main/java/edu/wpi/first/cscore/raw/RawSink.java

@@ -2,10 +2,10 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore.raw;
+package edu.wpi.first.cscore.raw;
 
-import edu.wpi.cscore.CameraServerJNI;
-import edu.wpi.cscore.ImageSink;
+import edu.wpi.first.cscore.CameraServerJNI;
+import edu.wpi.first.cscore.ImageSink;
 
 /**
  * A sink for user code to accept video frames as raw bytes.
@@ -28,6 +28,7 @@ public class RawSink extends ImageSink {
    * Wait for the next frame and get the image. Times out (returning 0) after 0.225 seconds. The
    * provided image will have three 8-bit channels stored in BGR order.
    *
+   * @param frame The frame object in which to store the image.
    * @return Frame time, or 0 on error (call getError() to obtain the error message); the frame time
    *     is in the same time base as wpi::Now(), and is in 1 us increments.
    */
@@ -39,6 +40,8 @@ public class RawSink extends ImageSink {
    * Wait for the next frame and get the image. Times out (returning 0) after timeout seconds. The
    * provided image will have three 8-bit channels stored in BGR order.
    *
+   * @param frame The frame object in which to store the image.
+   * @param timeout The frame timeout in seconds.
    * @return Frame time, or 0 on error (call getError() to obtain the error message); the frame time
    *     is in the same time base as wpi::Now(), and is in 1 us increments.
    */
@@ -50,6 +53,7 @@ public class RawSink extends ImageSink {
    * Wait for the next frame and get the image. May block forever. The provided image will have
    * three 8-bit channels stored in BGR order.
    *
+   * @param frame The frame object in which to store the image.
    * @return Frame time, or 0 on error (call getError() to obtain the error message); the frame time
    *     is in the same time base as wpi::Now(), and is in 1 us increments.
    */

cscore/src/main/java/edu/wpi/first/cscore/raw/RawSource.java

@@ -2,11 +2,11 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-package edu.wpi.cscore.raw;
+package edu.wpi.first.cscore.raw;
 
-import edu.wpi.cscore.CameraServerJNI;
-import edu.wpi.cscore.ImageSource;
-import edu.wpi.cscore.VideoMode;
+import edu.wpi.first.cscore.CameraServerJNI;
+import edu.wpi.first.cscore.ImageSource;
+import edu.wpi.first.cscore.VideoMode;
 
 /**
  * A source for user code to provide video frames as raw bytes.

cscore/src/main/native/cpp/ConfigurableSourceImpl.cpp

@@ -13,7 +13,7 @@
 
 using namespace cs;
 
-ConfigurableSourceImpl::ConfigurableSourceImpl(const wpi::Twine& name,
+ConfigurableSourceImpl::ConfigurableSourceImpl(std::string_view name,
                                                wpi::Logger& logger,
                                                Notifier& notifier,
                                                Telemetry& telemetry,
@@ -50,11 +50,11 @@ void ConfigurableSourceImpl::NumSinksEnabledChanged() {
   // ignore
 }
 
-void ConfigurableSourceImpl::NotifyError(const wpi::Twine& msg) {
+void ConfigurableSourceImpl::NotifyError(std::string_view msg) {
   PutError(msg, wpi::Now());
 }
 
-int ConfigurableSourceImpl::CreateProperty(const wpi::Twine& name,
+int ConfigurableSourceImpl::CreateProperty(std::string_view name,
                                            CS_PropertyKind kind, int minimum,
                                            int maximum, int step,
                                            int defaultValue, int value) {
@@ -75,12 +75,12 @@ int ConfigurableSourceImpl::CreateProperty(const wpi::Twine& name,
         value = prop.value;
       });
   m_notifier.NotifySourceProperty(*this, CS_SOURCE_PROPERTY_CREATED, name, ndx,
-                                  kind, value, wpi::Twine{});
+                                  kind, value, {});
   return ndx;
 }
 
 int ConfigurableSourceImpl::CreateProperty(
-    const wpi::Twine& name, CS_PropertyKind kind, int minimum, int maximum,
+    std::string_view name, CS_PropertyKind kind, int minimum, int maximum,
     int step, int defaultValue, int value,
     std::function<void(CS_Property property)> onChange) {
   // TODO
@@ -88,7 +88,7 @@ int ConfigurableSourceImpl::CreateProperty(
 }
 
 void ConfigurableSourceImpl::SetEnumPropertyChoices(
-    int property, wpi::ArrayRef<std::string> choices, CS_Status* status) {
+    int property, wpi::span<const std::string> choices, CS_Status* status) {
   std::scoped_lock lock(m_mutex);
   auto prop = GetProperty(property);
   if (!prop) {
@@ -99,8 +99,8 @@ void ConfigurableSourceImpl::SetEnumPropertyChoices(
     *status = CS_WRONG_PROPERTY_TYPE;
     return;
   }
-  prop->enumChoices = choices;
+  prop->enumChoices.assign(choices.begin(), choices.end());
   m_notifier.NotifySourceProperty(*this, CS_SOURCE_PROPERTY_CHOICES_UPDATED,
                                   prop->name, property, CS_PROP_ENUM,
-                                  prop->value, wpi::Twine{});
+                                  prop->value, {});
 }

cscore/src/main/native/cpp/ConfigurableSourceImpl.h

@@ -9,10 +9,10 @@
 #include <functional>
 #include <memory>
 #include <string>
+#include <string_view>
 #include <vector>
 
-#include <wpi/ArrayRef.h>
-#include <wpi/Twine.h>
+#include <wpi/span.h>
 
 #include "SourceImpl.h"
 
@@ -20,7 +20,7 @@ namespace cs {
 
 class ConfigurableSourceImpl : public SourceImpl {
  protected:
-  ConfigurableSourceImpl(const wpi::Twine& name, wpi::Logger& logger,
+  ConfigurableSourceImpl(std::string_view name, wpi::Logger& logger,
                          Notifier& notifier, Telemetry& telemetry,
                          const VideoMode& mode);
 
@@ -35,13 +35,14 @@ class ConfigurableSourceImpl : public SourceImpl {
   void NumSinksEnabledChanged() override;
 
   // OpenCV-specific functions
-  void NotifyError(const wpi::Twine& msg);
-  int CreateProperty(const wpi::Twine& name, CS_PropertyKind kind, int minimum,
+  void NotifyError(std::string_view msg);
+  int CreateProperty(std::string_view name, CS_PropertyKind kind, int minimum,
                      int maximum, int step, int defaultValue, int value);
-  int CreateProperty(const wpi::Twine& name, CS_PropertyKind kind, int minimum,
+  int CreateProperty(std::string_view name, CS_PropertyKind kind, int minimum,
                      int maximum, int step, int defaultValue, int value,
                      std::function<void(CS_Property property)> onChange);
-  void SetEnumPropertyChoices(int property, wpi::ArrayRef<std::string> choices,
+  void SetEnumPropertyChoices(int property,
+                              wpi::span<const std::string> choices,
                               CS_Status* status);
 
  private:

cscore/src/main/native/cpp/CvSinkImpl.cpp

@@ -18,14 +18,14 @@
 
 using namespace cs;
 
-CvSinkImpl::CvSinkImpl(const wpi::Twine& name, wpi::Logger& logger,
+CvSinkImpl::CvSinkImpl(std::string_view name, wpi::Logger& logger,
                        Notifier& notifier, Telemetry& telemetry)
     : SinkImpl{name, logger, notifier, telemetry} {
   m_active = true;
   // m_thread = std::thread(&CvSinkImpl::ThreadMain, this);
 }
 
-CvSinkImpl::CvSinkImpl(const wpi::Twine& name, wpi::Logger& logger,
+CvSinkImpl::CvSinkImpl(std::string_view name, wpi::Logger& logger,
                        Notifier& notifier, Telemetry& telemetry,
                        std::function<void(uint64_t time)> processFrame)
     : SinkImpl{name, logger, notifier, telemetry} {}
@@ -110,7 +110,7 @@ void CvSinkImpl::ThreadMain() {
       std::this_thread::sleep_for(std::chrono::seconds(1));
       continue;
     }
-    SDEBUG4("waiting for frame");
+    SDEBUG4("{}", "waiting for frame");
     Frame frame = source->GetNextFrame();  // blocks
     if (!m_active) {
       break;
@@ -127,14 +127,14 @@ void CvSinkImpl::ThreadMain() {
 
 namespace cs {
 
-CS_Sink CreateCvSink(const wpi::Twine& name, CS_Status* status) {
+CS_Sink CreateCvSink(std::string_view name, CS_Status* status) {
   auto& inst = Instance::GetInstance();
   return inst.CreateSink(
       CS_SINK_CV, std::make_shared<CvSinkImpl>(name, inst.logger, inst.notifier,
                                                inst.telemetry));
 }
 
-CS_Sink CreateCvSinkCallback(const wpi::Twine& name,
+CS_Sink CreateCvSinkCallback(std::string_view name,
                              std::function<void(uint64_t time)> processFrame,
                              CS_Status* status) {
   auto& inst = Instance::GetInstance();
@@ -145,7 +145,7 @@ CS_Sink CreateCvSinkCallback(const wpi::Twine& name,
 
 static constexpr unsigned SinkMask = CS_SINK_CV | CS_SINK_RAW;
 
-void SetSinkDescription(CS_Sink sink, const wpi::Twine& description,
+void SetSinkDescription(CS_Sink sink, std::string_view description,
                         CS_Status* status) {
   auto data = Instance::GetInstance().GetSink(sink);
   if (!data || (data->kind & SinkMask) == 0) {
@@ -183,12 +183,12 @@ std::string GetSinkError(CS_Sink sink, CS_Status* status) {
   return static_cast<CvSinkImpl&>(*data->sink).GetError();
 }
 
-wpi::StringRef GetSinkError(CS_Sink sink, wpi::SmallVectorImpl<char>& buf,
-                            CS_Status* status) {
+std::string_view GetSinkError(CS_Sink sink, wpi::SmallVectorImpl<char>& buf,
+                              CS_Status* status) {
   auto data = Instance::GetInstance().GetSink(sink);
   if (!data || (data->kind & SinkMask) == 0) {
     *status = CS_INVALID_HANDLE;
-    return wpi::StringRef{};
+    return {};
   }
   return static_cast<CvSinkImpl&>(*data->sink).GetError(buf);
 }

cscore/src/main/native/cpp/CvSinkImpl.h

@@ -9,10 +9,10 @@
 
 #include <atomic>
 #include <functional>
+#include <string_view>
 #include <thread>
 
 #include <opencv2/core/core.hpp>
-#include <wpi/Twine.h>
 #include <wpi/condition_variable.h>
 
 #include "Frame.h"
@@ -24,9 +24,9 @@ class SourceImpl;
 
 class CvSinkImpl : public SinkImpl {
  public:
-  CvSinkImpl(const wpi::Twine& name, wpi::Logger& logger, Notifier& notifier,
+  CvSinkImpl(std::string_view name, wpi::Logger& logger, Notifier& notifier,
              Telemetry& telemetry);
-  CvSinkImpl(const wpi::Twine& name, wpi::Logger& logger, Notifier& notifier,
+  CvSinkImpl(std::string_view name, wpi::Logger& logger, Notifier& notifier,
              Telemetry& telemetry,
              std::function<void(uint64_t time)> processFrame);
   ~CvSinkImpl() override;

cscore/src/main/native/cpp/CvSourceImpl.cpp

@@ -7,7 +7,6 @@
 #include <opencv2/core/core.hpp>
 #include <opencv2/highgui/highgui.hpp>
 #include <opencv2/imgproc/imgproc.hpp>
-#include <wpi/STLExtras.h>
 #include <wpi/timestamp.h>
 
 #include "Handle.h"
@@ -19,7 +18,7 @@
 
 using namespace cs;
 
-CvSourceImpl::CvSourceImpl(const wpi::Twine& name, wpi::Logger& logger,
+CvSourceImpl::CvSourceImpl(std::string_view name, wpi::Logger& logger,
                            Notifier& notifier, Telemetry& telemetry,
                            const VideoMode& mode)
     : ConfigurableSourceImpl{name, logger, notifier, telemetry, mode} {}
@@ -53,8 +52,7 @@ void CvSourceImpl::PutFrame(cv::Mat& image) {
       cv::cvtColor(finalImage, dest->AsMat(), cv::COLOR_BGRA2BGR);
       break;
     default:
-      SERROR("PutFrame: " << image.channels()
-                          << "-channel images not supported");
+      SERROR("PutFrame: {}-channel images not supported", image.channels());
       return;
   }
   SourceImpl::PutFrame(std::move(dest), wpi::Now());
@@ -62,7 +60,7 @@ void CvSourceImpl::PutFrame(cv::Mat& image) {
 
 namespace cs {
 
-CS_Source CreateCvSource(const wpi::Twine& name, const VideoMode& mode,
+CS_Source CreateCvSource(std::string_view name, const VideoMode& mode,
                          CS_Status* status) {
   auto& inst = Instance::GetInstance();
   return inst.CreateSource(CS_SOURCE_CV, std::make_shared<CvSourceImpl>(
@@ -81,7 +79,7 @@ void PutSourceFrame(CS_Source source, cv::Mat& image, CS_Status* status) {
 
 static constexpr unsigned SourceMask = CS_SINK_CV | CS_SINK_RAW;
 
-void NotifySourceError(CS_Source source, const wpi::Twine& msg,
+void NotifySourceError(CS_Source source, std::string_view msg,
                        CS_Status* status) {
   auto data = Instance::GetInstance().GetSource(source);
   if (!data || (data->kind & SourceMask) == 0) {
@@ -100,7 +98,7 @@ void SetSourceConnected(CS_Source source, bool connected, CS_Status* status) {
   static_cast<CvSourceImpl&>(*data->source).SetConnected(connected);
 }
 
-void SetSourceDescription(CS_Source source, const wpi::Twine& description,
+void SetSourceDescription(CS_Source source, std::string_view description,
                           CS_Status* status) {
   auto data = Instance::GetInstance().GetSource(source);
   if (!data || (data->kind & SourceMask) == 0) {
@@ -110,7 +108,7 @@ void SetSourceDescription(CS_Source source, const wpi::Twine& description,
   static_cast<CvSourceImpl&>(*data->source).SetDescription(description);
 }
 
-CS_Property CreateSourceProperty(CS_Source source, const wpi::Twine& name,
+CS_Property CreateSourceProperty(CS_Source source, std::string_view name,
                                  CS_PropertyKind kind, int minimum, int maximum,
                                  int step, int defaultValue, int value,
                                  CS_Status* status) {
@@ -126,7 +124,7 @@ CS_Property CreateSourceProperty(CS_Source source, const wpi::Twine& name,
 }
 
 CS_Property CreateSourcePropertyCallback(
-    CS_Source source, const wpi::Twine& name, CS_PropertyKind kind, int minimum,
+    CS_Source source, std::string_view name, CS_PropertyKind kind, int minimum,
     int maximum, int step, int defaultValue, int value,
     std::function<void(CS_Property property)> onChange, CS_Status* status) {
   auto data = Instance::GetInstance().GetSource(source);
@@ -141,7 +139,7 @@ CS_Property CreateSourcePropertyCallback(
 }
 
 void SetSourceEnumPropertyChoices(CS_Source source, CS_Property property,
-                                  wpi::ArrayRef<std::string> choices,
+                                  wpi::span<const std::string> choices,
                                   CS_Status* status) {
   auto data = Instance::GetInstance().GetSource(source);
   if (!data || (data->kind & SourceMask) == 0) {

cscore/src/main/native/cpp/CvSourceImpl.h

@@ -9,11 +9,10 @@
 #include <functional>
 #include <memory>
 #include <string>
+#include <string_view>
 #include <vector>
 
 #include <opencv2/core/core.hpp>
-#include <wpi/ArrayRef.h>
-#include <wpi/Twine.h>
 
 #include "ConfigurableSourceImpl.h"
 #include "SourceImpl.h"
@@ -22,7 +21,7 @@ namespace cs {
 
 class CvSourceImpl : public ConfigurableSourceImpl {
  public:
-  CvSourceImpl(const wpi::Twine& name, wpi::Logger& logger, Notifier& notifier,
+  CvSourceImpl(std::string_view name, wpi::Logger& logger, Notifier& notifier,
                Telemetry& telemetry, const VideoMode& mode);
   ~CvSourceImpl() override;
 

cscore/src/main/native/cpp/Frame.cpp

@@ -16,10 +16,10 @@
 
 using namespace cs;
 
-Frame::Frame(SourceImpl& source, const wpi::Twine& error, Time time)
+Frame::Frame(SourceImpl& source, std::string_view error, Time time)
     : m_impl{source.AllocFrameImpl().release()} {
   m_impl->refcount = 1;
-  m_impl->error = error.str();
+  m_impl->error = error;
   m_impl->time = time;
 }
 
@@ -522,10 +522,8 @@ Image* Frame::GetImageImpl(int width, int height,
   }
 
   WPI_DEBUG4(Instance::GetInstance().logger,
-             "converting image from " << cur->width << "x" << cur->height
-                                      << " type " << cur->pixelFormat << " to "
-                                      << width << "x" << height << " type "
-                                      << pixelFormat);
+             "converting image from {}x{} type {} to {}x{} type {}", cur->width,
+             cur->height, cur->pixelFormat, width, height, pixelFormat);
 
   // If the source image is a JPEG, we need to decode it before we can do
   // anything else with it.  Note that if the destination format is JPEG, we

cscore/src/main/native/cpp/Frame.h

@@ -8,11 +8,11 @@
 #include <atomic>
 #include <memory>
 #include <string>
+#include <string_view>
 #include <utility>
 #include <vector>
 
 #include <wpi/SmallVector.h>
-#include <wpi/Twine.h>
 #include <wpi/mutex.h>
 
 #include "Image.h"
@@ -44,7 +44,7 @@ class Frame {
  public:
   Frame() noexcept = default;
 
-  Frame(SourceImpl& source, const wpi::Twine& error, Time time);
+  Frame(SourceImpl& source, std::string_view error, Time time);
 
   Frame(SourceImpl& source, std::unique_ptr<Image> image, Time time);
 
@@ -72,7 +72,7 @@ class Frame {
 
   Time GetTime() const { return m_impl ? m_impl->time : 0; }
 
-  wpi::StringRef GetError() const {
+  std::string_view GetError() const {
     if (!m_impl) {
       return {};
     }

cscore/src/main/native/cpp/Handle.h

@@ -22,7 +22,8 @@ class Handle {
     kSource,
     kSink,
     kListener,
-    kSinkProperty
+    kSinkProperty,
+    kListenerPoller
   };
   enum { kIndexMax = 0xffff };
 

cscore/src/main/native/cpp/HttpCameraImpl.cpp

@@ -5,6 +5,7 @@
 #include "HttpCameraImpl.h"
 
 #include <wpi/MemAlloc.h>
+#include <wpi/StringExtras.h>
 #include <wpi/TCPConnector.h>
 #include <wpi/timestamp.h>
 
@@ -18,7 +19,7 @@
 
 using namespace cs;
 
-HttpCameraImpl::HttpCameraImpl(const wpi::Twine& name, CS_HttpCameraKind kind,
+HttpCameraImpl::HttpCameraImpl(std::string_view name, CS_HttpCameraKind kind,
                                wpi::Logger& logger, Notifier& notifier,
                                Telemetry& telemetry)
     : SourceImpl{name, logger, notifier, telemetry}, m_kind{kind} {}
@@ -84,7 +85,7 @@ void HttpCameraImpl::MonitorThreadMain() {
     // (this will result in an error at the read point, and ultimately
     // a reconnect attempt)
     if (m_streamConn && m_frameCount == 0) {
-      SWARNING("Monitor detected stream hung, disconnecting");
+      SWARNING("{}", "Monitor detected stream hung, disconnecting");
       m_streamConn->stream->close();
     }
 
@@ -92,7 +93,7 @@ void HttpCameraImpl::MonitorThreadMain() {
     m_frameCount = 0;
   }
 
-  SDEBUG("Monitor Thread exiting");
+  SDEBUG("{}", "Monitor Thread exiting");
 }
 
 void HttpCameraImpl::StreamThreadMain() {
@@ -132,14 +133,14 @@ void HttpCameraImpl::StreamThreadMain() {
     SetConnected(true);
 
     // stream
-    DeviceStream(conn->is, boundary);
+    DeviceStream(conn->is, boundary.str());
     {
       std::unique_lock lock(m_mutex);
       m_streamConn = nullptr;
     }
   }
 
-  SDEBUG("Camera Thread exiting");
+  SDEBUG("{}", "Camera Thread exiting");
   SetConnected(false);
 }
 
@@ -150,7 +151,7 @@ wpi::HttpConnection* HttpCameraImpl::DeviceStreamConnect(
   {
     std::scoped_lock lock(m_mutex);
     if (m_locations.empty()) {
-      SERROR("locations array is empty!?");
+      SERROR("{}", "locations array is empty!?");
       std::this_thread::sleep_for(std::chrono::seconds(1));
       return nullptr;
     }
@@ -181,19 +182,17 @@ wpi::HttpConnection* HttpCameraImpl::DeviceStreamConnect(
 
   std::string warn;
   if (!conn->Handshake(req, &warn)) {
-    SWARNING(GetName() << ": " << warn);
+    SWARNING("{}", warn);
     std::scoped_lock lock(m_mutex);
     m_streamConn = nullptr;
     return nullptr;
   }
 
   // Parse Content-Type header to get the boundary
-  wpi::StringRef mediaType, contentType;
-  std::tie(mediaType, contentType) = conn->contentType.str().split(';');
-  mediaType = mediaType.trim();
+  auto [mediaType, contentType] = wpi::split(conn->contentType.str(), ';');
+  mediaType = wpi::trim(mediaType);
   if (mediaType != "multipart/x-mixed-replace") {
-    SWARNING("\"" << req.host << "\": unrecognized Content-Type \"" << mediaType
-                  << "\"");
+    SWARNING("\"{}\": unrecognized Content-Type \"{}\"", req.host, mediaType);
     std::scoped_lock lock(m_mutex);
     m_streamConn = nullptr;
     return nullptr;
@@ -202,14 +201,13 @@ wpi::HttpConnection* HttpCameraImpl::DeviceStreamConnect(
   // media parameters
   boundary.clear();
   while (!contentType.empty()) {
-    wpi::StringRef keyvalue;
-    std::tie(keyvalue, contentType) = contentType.split(';');
-    contentType = contentType.ltrim();
-    wpi::StringRef key, value;
-    std::tie(key, value) = keyvalue.split('=');
-    if (key.trim() == "boundary") {
-      value = value.trim().trim('"');  // value may be quoted
-      if (value.startswith("--")) {
+    std::string_view keyvalue;
+    std::tie(keyvalue, contentType) = wpi::split(contentType, ';');
+    contentType = wpi::ltrim(contentType);
+    auto [key, value] = wpi::split(keyvalue, '=');
+    if (wpi::trim(key) == "boundary") {
+      value = wpi::trim(wpi::trim(value), '"');  // value may be quoted
+      if (wpi::starts_with(value, "--")) {
         value = value.substr(2);
       }
       boundary.append(value.begin(), value.end());
@@ -217,8 +215,7 @@ wpi::HttpConnection* HttpCameraImpl::DeviceStreamConnect(
   }
 
   if (boundary.empty()) {
-    SWARNING("\"" << req.host
-                  << "\": empty multi-part boundary or no Content-Type");
+    SWARNING("\"{}\": empty multi-part boundary or no Content-Type", req.host);
     std::scoped_lock lock(m_mutex);
     m_streamConn = nullptr;
     return nullptr;
@@ -228,7 +225,7 @@ wpi::HttpConnection* HttpCameraImpl::DeviceStreamConnect(
 }
 
 void HttpCameraImpl::DeviceStream(wpi::raw_istream& is,
-                                  wpi::StringRef boundary) {
+                                  std::string_view boundary) {
   // Stored here so we reuse it from frame to frame
   std::string imageBuf;
 
@@ -275,28 +272,29 @@ bool HttpCameraImpl::DeviceStreamFrame(wpi::raw_istream& is,
   wpi::SmallString<64> contentTypeBuf;
   wpi::SmallString<64> contentLengthBuf;
   if (!ParseHttpHeaders(is, &contentTypeBuf, &contentLengthBuf)) {
-    SWARNING("disconnected during headers");
+    SWARNING("{}", "disconnected during headers");
     PutError("disconnected during headers", wpi::Now());
     return false;
   }
 
   // Check the content type (if present)
   if (!contentTypeBuf.str().empty() &&
-      !contentTypeBuf.str().startswith("image/jpeg")) {
-    wpi::SmallString<64> errBuf;
-    wpi::raw_svector_ostream errMsg{errBuf};
-    errMsg << "received unknown Content-Type \"" << contentTypeBuf << "\"";
-    SWARNING(errMsg.str());
-    PutError(errMsg.str(), wpi::Now());
+      !wpi::starts_with(contentTypeBuf, "image/jpeg")) {
+    auto errMsg =
+        fmt::format("received unknown Content-Type \"{}\"", contentTypeBuf);
+    SWARNING("{}", errMsg);
+    PutError(errMsg, wpi::Now());
     return false;
   }
 
   unsigned int contentLength = 0;
-  if (contentLengthBuf.str().getAsInteger(10, contentLength)) {
+  if (auto v = wpi::parse_integer<unsigned int>(contentLengthBuf, 10)) {
+    contentLength = v.value();
+  } else {
     // Ugh, no Content-Length?  Read the blocks of the JPEG file.
     int width, height;
     if (!ReadJpeg(is, imageBuf, &width, &height)) {
-      SWARNING("did not receive a JPEG image");
+      SWARNING("{}", "did not receive a JPEG image");
       PutError("did not receive a JPEG image", wpi::Now());
       return false;
     }
@@ -315,7 +313,7 @@ bool HttpCameraImpl::DeviceStreamFrame(wpi::raw_istream& is,
   }
   int width, height;
   if (!GetJpegSize(image->str(), &width, &height)) {
-    SWARNING("did not receive a JPEG image");
+    SWARNING("{}", "did not receive a JPEG image");
     PutError("did not receive a JPEG image", wpi::Now());
     return false;
   }
@@ -345,7 +343,7 @@ void HttpCameraImpl::SettingsThreadMain() {
     DeviceSendSettings(req);
   }
 
-  SDEBUG("Settings Thread exiting");
+  SDEBUG("{}", "Settings Thread exiting");
 }
 
 void HttpCameraImpl::DeviceSendSettings(wpi::HttpRequest& req) {
@@ -369,7 +367,7 @@ void HttpCameraImpl::DeviceSendSettings(wpi::HttpRequest& req) {
   // Just need a handshake as settings are sent via GET parameters
   std::string warn;
   if (!conn->Handshake(req, &warn)) {
-    SWARNING(GetName() << ": " << warn);
+    SWARNING("{}", warn);
   }
 
   conn->stream->close();
@@ -380,7 +378,7 @@ CS_HttpCameraKind HttpCameraImpl::GetKind() const {
   return m_kind;
 }
 
-bool HttpCameraImpl::SetUrls(wpi::ArrayRef<std::string> urls,
+bool HttpCameraImpl::SetUrls(wpi::span<const std::string> urls,
                              CS_Status* status) {
   std::vector<wpi::HttpLocation> locations;
   for (const auto& url : urls) {
@@ -388,7 +386,7 @@ bool HttpCameraImpl::SetUrls(wpi::ArrayRef<std::string> urls,
     std::string errorMsg;
     locations.emplace_back(url, &error, &errorMsg);
     if (error) {
-      SERROR(GetName() << ": " << errorMsg);
+      SERROR("{}", errorMsg);
       *status = CS_BAD_URL;
       return false;
     }
@@ -410,8 +408,8 @@ std::vector<std::string> HttpCameraImpl::GetUrls() const {
   return urls;
 }
 
-void HttpCameraImpl::CreateProperty(const wpi::Twine& name,
-                                    const wpi::Twine& httpParam,
+void HttpCameraImpl::CreateProperty(std::string_view name,
+                                    std::string_view httpParam,
                                     bool viaSettings, CS_PropertyKind kind,
                                     int minimum, int maximum, int step,
                                     int defaultValue, int value) const {
@@ -421,13 +419,12 @@ void HttpCameraImpl::CreateProperty(const wpi::Twine& name,
       value));
 
   m_notifier.NotifySourceProperty(*this, CS_SOURCE_PROPERTY_CREATED, name,
-                                  m_propertyData.size() + 1, kind, value,
-                                  wpi::Twine{});
+                                  m_propertyData.size() + 1, kind, value, {});
 }
 
 template <typename T>
 void HttpCameraImpl::CreateEnumProperty(
-    const wpi::Twine& name, const wpi::Twine& httpParam, bool viaSettings,
+    std::string_view name, std::string_view httpParam, bool viaSettings,
     int defaultValue, int value, std::initializer_list<T> choices) const {
   std::scoped_lock lock(m_mutex);
   m_propertyData.emplace_back(std::make_unique<PropertyData>(
@@ -442,14 +439,14 @@ void HttpCameraImpl::CreateEnumProperty(
 
   m_notifier.NotifySourceProperty(*this, CS_SOURCE_PROPERTY_CREATED, name,
                                   m_propertyData.size() + 1, CS_PROP_ENUM,
-                                  value, wpi::Twine{});
+                                  value, {});
   m_notifier.NotifySourceProperty(*this, CS_SOURCE_PROPERTY_CHOICES_UPDATED,
                                   name, m_propertyData.size() + 1, CS_PROP_ENUM,
-                                  value, wpi::Twine{});
+                                  value, {});
 }
 
 std::unique_ptr<PropertyImpl> HttpCameraImpl::CreateEmptyProperty(
-    const wpi::Twine& name) const {
+    std::string_view name) const {
   return std::make_unique<PropertyData>(name);
 }
 
@@ -474,7 +471,7 @@ void HttpCameraImpl::SetProperty(int property, int value, CS_Status* status) {
   // TODO
 }
 
-void HttpCameraImpl::SetStringProperty(int property, const wpi::Twine& value,
+void HttpCameraImpl::SetStringProperty(int property, std::string_view value,
                                        CS_Status* status) {
   // TODO
 }
@@ -560,7 +557,7 @@ bool AxisCameraImpl::CacheProperties(CS_Status* status) const {
 
 namespace cs {
 
-CS_Source CreateHttpCamera(const wpi::Twine& name, const wpi::Twine& url,
+CS_Source CreateHttpCamera(std::string_view name, std::string_view url,
                            CS_HttpCameraKind kind, CS_Status* status) {
   auto& inst = Instance::GetInstance();
   std::shared_ptr<HttpCameraImpl> source;
@@ -574,14 +571,15 @@ CS_Source CreateHttpCamera(const wpi::Twine& name, const wpi::Twine& url,
                                                 inst.notifier, inst.telemetry);
       break;
   }
-  if (!source->SetUrls(url.str(), status)) {
+  std::string urlStr{url};
+  if (!source->SetUrls(wpi::span{&urlStr, 1}, status)) {
     return 0;
   }
   return inst.CreateSource(CS_SOURCE_HTTP, source);
 }
 
-CS_Source CreateHttpCamera(const wpi::Twine& name,
-                           wpi::ArrayRef<std::string> urls,
+CS_Source CreateHttpCamera(std::string_view name,
+                           wpi::span<const std::string> urls,
                            CS_HttpCameraKind kind, CS_Status* status) {
   auto& inst = Instance::GetInstance();
   if (urls.empty()) {
@@ -605,7 +603,7 @@ CS_HttpCameraKind GetHttpCameraKind(CS_Source source, CS_Status* status) {
   return static_cast<HttpCameraImpl&>(*data->source).GetKind();
 }
 
-void SetHttpCameraUrls(CS_Source source, wpi::ArrayRef<std::string> urls,
+void SetHttpCameraUrls(CS_Source source, wpi::span<const std::string> urls,
                        CS_Status* status) {
   if (urls.empty()) {
     *status = CS_EMPTY_VALUE;

cscore/src/main/native/cpp/HttpCameraImpl.h

@@ -10,15 +10,16 @@
 #include <initializer_list>
 #include <memory>
 #include <string>
+#include <string_view>
 #include <thread>
 #include <vector>
 
 #include <wpi/HttpUtil.h>
 #include <wpi/SmallString.h>
 #include <wpi/StringMap.h>
-#include <wpi/Twine.h>
 #include <wpi/condition_variable.h>
 #include <wpi/raw_istream.h>
+#include <wpi/span.h>
 
 #include "SourceImpl.h"
 #include "cscore_cpp.h"
@@ -27,7 +28,7 @@ namespace cs {
 
 class HttpCameraImpl : public SourceImpl {
  public:
-  HttpCameraImpl(const wpi::Twine& name, CS_HttpCameraKind kind,
+  HttpCameraImpl(std::string_view name, CS_HttpCameraKind kind,
                  wpi::Logger& logger, Notifier& notifier, Telemetry& telemetry);
   ~HttpCameraImpl() override;
 
@@ -35,7 +36,7 @@ class HttpCameraImpl : public SourceImpl {
 
   // Property functions
   void SetProperty(int property, int value, CS_Status* status) override;
-  void SetStringProperty(int property, const wpi::Twine& value,
+  void SetStringProperty(int property, std::string_view value,
                          CS_Status* status) override;
 
   // Standard common camera properties
@@ -54,20 +55,20 @@ class HttpCameraImpl : public SourceImpl {
   void NumSinksEnabledChanged() override;
 
   CS_HttpCameraKind GetKind() const;
-  bool SetUrls(wpi::ArrayRef<std::string> urls, CS_Status* status);
+  bool SetUrls(wpi::span<const std::string> urls, CS_Status* status);
   std::vector<std::string> GetUrls() const;
 
   // Property data
   class PropertyData : public PropertyImpl {
    public:
     PropertyData() = default;
-    explicit PropertyData(const wpi::Twine& name_) : PropertyImpl{name_} {}
-    PropertyData(const wpi::Twine& name_, const wpi::Twine& httpParam_,
+    explicit PropertyData(std::string_view name_) : PropertyImpl{name_} {}
+    PropertyData(std::string_view name_, std::string_view httpParam_,
                  bool viaSettings_, CS_PropertyKind kind_, int minimum_,
                  int maximum_, int step_, int defaultValue_, int value_)
         : PropertyImpl(name_, kind_, step_, defaultValue_, value_),
           viaSettings(viaSettings_),
-          httpParam(httpParam_.str()) {
+          httpParam(httpParam_) {
       hasMinimum = true;
       minimum = minimum_;
       hasMaximum = true;
@@ -81,16 +82,16 @@ class HttpCameraImpl : public SourceImpl {
 
  protected:
   std::unique_ptr<PropertyImpl> CreateEmptyProperty(
-      const wpi::Twine& name) const override;
+      std::string_view name) const override;
 
   bool CacheProperties(CS_Status* status) const override;
 
-  void CreateProperty(const wpi::Twine& name, const wpi::Twine& httpParam,
+  void CreateProperty(std::string_view name, std::string_view httpParam,
                       bool viaSettings, CS_PropertyKind kind, int minimum,
                       int maximum, int step, int defaultValue, int value) const;
 
   template <typename T>
-  void CreateEnumProperty(const wpi::Twine& name, const wpi::Twine& httpParam,
+  void CreateEnumProperty(std::string_view name, std::string_view httpParam,
                           bool viaSettings, int defaultValue, int value,
                           std::initializer_list<T> choices) const;
 
@@ -101,7 +102,7 @@ class HttpCameraImpl : public SourceImpl {
   // Functions used by StreamThreadMain()
   wpi::HttpConnection* DeviceStreamConnect(
       wpi::SmallVectorImpl<char>& boundary);
-  void DeviceStream(wpi::raw_istream& is, wpi::StringRef boundary);
+  void DeviceStream(wpi::raw_istream& is, std::string_view boundary);
   bool DeviceStreamFrame(wpi::raw_istream& is, std::string& imageBuf);
 
   // The camera settings thread
@@ -146,12 +147,12 @@ class HttpCameraImpl : public SourceImpl {
 
 class AxisCameraImpl : public HttpCameraImpl {
  public:
-  AxisCameraImpl(const wpi::Twine& name, wpi::Logger& logger,
-                 Notifier& notifier, Telemetry& telemetry)
+  AxisCameraImpl(std::string_view name, wpi::Logger& logger, Notifier& notifier,
+                 Telemetry& telemetry)
       : HttpCameraImpl{name, CS_HTTP_AXIS, logger, notifier, telemetry} {}
 #if 0
   void SetProperty(int property, int value, CS_Status* status) override;
-  void SetStringProperty(int property, const wpi::Twine& value,
+  void SetStringProperty(int property, std::string_view value,
                          CS_Status* status) override;
 #endif
  protected:

cscore/src/main/native/cpp/Image.h

@@ -5,10 +5,10 @@
 #ifndef CSCORE_IMAGE_H_
 #define CSCORE_IMAGE_H_
 
+#include <string_view>
 #include <vector>
 
 #include <opencv2/core/core.hpp>
-#include <wpi/StringRef.h>
 
 #include "cscore_cpp.h"
 #include "default_init_allocator.h"
@@ -34,8 +34,8 @@ class Image {
   Image& operator=(const Image&) = delete;
 
   // Getters
-  operator wpi::StringRef() const { return str(); }  // NOLINT
-  wpi::StringRef str() const { return wpi::StringRef(data(), size()); }
+  operator std::string_view() const { return str(); }  // NOLINT
+  std::string_view str() const { return {data(), size()}; }
   size_t capacity() const { return m_data.capacity(); }
   const char* data() const {
     return reinterpret_cast<const char*>(m_data.data());

cscore/src/main/native/cpp/Instance.cpp

@@ -4,39 +4,38 @@
 
 #include "Instance.h"
 
-#include <wpi/Path.h>
-#include <wpi/SmallString.h>
-#include <wpi/StringRef.h>
-#include <wpi/raw_ostream.h>
+#include <string_view>
+
+#include <fmt/format.h>
+#include <wpi/fs.h>
 
 using namespace cs;
 
 static void def_log_func(unsigned int level, const char* file,
                          unsigned int line, const char* msg) {
-  wpi::SmallString<128> buf;
-  wpi::raw_svector_ostream oss(buf);
   if (level == 20) {
-    oss << "CS: " << msg << '\n';
-    wpi::errs() << oss.str();
+    fmt::print(stderr, "CS: {}\n", msg);
     return;
   }
 
-  wpi::StringRef levelmsg;
+  std::string_view levelmsg;
   if (level >= 50) {
-    levelmsg = "CRITICAL: ";
+    levelmsg = "CRITICAL";
   } else if (level >= 40) {
-    levelmsg = "ERROR: ";
+    levelmsg = "ERROR";
   } else if (level >= 30) {
-    levelmsg = "WARNING: ";
+    levelmsg = "WARNING";
   } else {
     return;
   }
-  oss << "CS: " << levelmsg << msg << " (" << wpi::sys::path::filename(file)
-      << ':' << line << ")\n";
-  wpi::errs() << oss.str();
+  fmt::print(stderr, "CS: {}: {} ({}:{})\n", levelmsg, msg,
+             fs::path{file}.filename().string(), line);
 }
 
-Instance::Instance() : telemetry(notifier), networkListener(logger, notifier) {
+Instance::Instance()
+    : telemetry(notifier),
+      networkListener(logger, notifier),
+      usbCameraListener(logger, notifier) {
   SetDefaultLogger();
 }
 
@@ -52,6 +51,7 @@ void Instance::Shutdown() {
   m_sinks.FreeAll();
   m_sources.FreeAll();
   networkListener.Stop();
+  usbCameraListener.Stop();
   telemetry.Stop();
   notifier.Stop();
 }

cscore/src/main/native/cpp/Instance.h

@@ -18,6 +18,7 @@
 #include "SourceImpl.h"
 #include "Telemetry.h"
 #include "UnlimitedHandleResource.h"
+#include "UsbCameraListener.h"
 
 namespace cs {
 
@@ -54,6 +55,7 @@ class Instance {
   Notifier notifier;
   Telemetry telemetry;
   NetworkListener networkListener;
+  UsbCameraListener usbCameraListener;
 
  private:
   UnlimitedHandleResource<Handle, SourceData, Handle::kSource> m_sources;
@@ -84,18 +86,17 @@ class Instance {
   void DestroySource(CS_Source handle);
   void DestroySink(CS_Sink handle);
 
-  wpi::ArrayRef<CS_Source> EnumerateSourceHandles(
+  wpi::span<CS_Source> EnumerateSourceHandles(
       wpi::SmallVectorImpl<CS_Source>& vec) {
     return m_sources.GetAll(vec);
   }
 
-  wpi::ArrayRef<CS_Sink> EnumerateSinkHandles(
-      wpi::SmallVectorImpl<CS_Sink>& vec) {
+  wpi::span<CS_Sink> EnumerateSinkHandles(wpi::SmallVectorImpl<CS_Sink>& vec) {
     return m_sinks.GetAll(vec);
   }
 
-  wpi::ArrayRef<CS_Sink> EnumerateSourceSinks(
-      CS_Source source, wpi::SmallVectorImpl<CS_Sink>& vec) {
+  wpi::span<CS_Sink> EnumerateSourceSinks(CS_Source source,
+                                          wpi::SmallVectorImpl<CS_Sink>& vec) {
     vec.clear();
     m_sinks.ForEach([&](CS_Sink sinkHandle, const SinkData& data) {
       if (source == data.sourceHandle.load()) {

cscore/src/main/native/cpp/JpegUtil.cpp

@@ -46,20 +46,20 @@ static const unsigned char dhtData[] = {
     0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
     0xe8, 0xe9, 0xea, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9, 0xfa};
 
-bool IsJpeg(wpi::StringRef data) {
+bool IsJpeg(std::string_view data) {
   if (data.size() < 11) {
     return false;
   }
 
   // Check for valid SOI
-  auto bytes = data.bytes_begin();
+  auto bytes = reinterpret_cast<const unsigned char*>(data.data());
   if (bytes[0] != 0xff || bytes[1] != 0xd8) {
     return false;
   }
   return true;
 }
 
-bool GetJpegSize(wpi::StringRef data, int* width, int* height) {
+bool GetJpegSize(std::string_view data, int* width, int* height) {
   if (!IsJpeg(data)) {
     return false;
   }
@@ -69,7 +69,7 @@ bool GetJpegSize(wpi::StringRef data, int* width, int* height) {
     if (data.size() < 4) {
       return false;  // EOF
     }
-    auto bytes = data.bytes_begin();
+    auto bytes = reinterpret_cast<const unsigned char*>(data.data());
     if (bytes[0] != 0xff) {
       return false;  // not a tag
     }
@@ -94,7 +94,7 @@ bool GetJpegSize(wpi::StringRef data, int* width, int* height) {
 }
 
 bool JpegNeedsDHT(const char* data, size_t* size, size_t* locSOF) {
-  wpi::StringRef sdata(data, *size);
+  std::string_view sdata(data, *size);
   if (!IsJpeg(sdata)) {
     return false;
   }
@@ -107,7 +107,7 @@ bool JpegNeedsDHT(const char* data, size_t* size, size_t* locSOF) {
     if (sdata.size() < 4) {
       return false;  // EOF
     }
-    auto bytes = sdata.bytes_begin();
+    auto bytes = reinterpret_cast<const unsigned char*>(sdata.data());
     if (bytes[0] != 0xff) {
       return false;  // not a tag
     }
@@ -132,9 +132,8 @@ bool JpegNeedsDHT(const char* data, size_t* size, size_t* locSOF) {
   return false;
 }
 
-wpi::StringRef JpegGetDHT() {
-  return wpi::StringRef(reinterpret_cast<const char*>(dhtData),
-                        sizeof(dhtData));
+std::string_view JpegGetDHT() {
+  return {reinterpret_cast<const char*>(dhtData), sizeof(dhtData)};
 }
 
 static inline void ReadInto(wpi::raw_istream& is, std::string& buf,

cscore/src/main/native/cpp/JpegUtil.h

@@ -6,8 +6,7 @@
 #define CSCORE_JPEGUTIL_H_
 
 #include <string>
-
-#include <wpi/StringRef.h>
+#include <string_view>
 
 namespace wpi {
 class raw_istream;
@@ -15,13 +14,13 @@ class raw_istream;
 
 namespace cs {
 
-bool IsJpeg(wpi::StringRef data);
+bool IsJpeg(std::string_view data);
 
-bool GetJpegSize(wpi::StringRef data, int* width, int* height);
+bool GetJpegSize(std::string_view data, int* width, int* height);
 
 bool JpegNeedsDHT(const char* data, size_t* size, size_t* locSOF);
 
-wpi::StringRef JpegGetDHT();
+std::string_view JpegGetDHT();
 
 bool ReadJpeg(wpi::raw_istream& is, std::string& buf, int* width, int* height);
 

cscore/src/main/native/cpp/Log.cpp

@@ -0,0 +1,15 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "Log.h"
+
+void cs::NamedLogV(wpi::Logger& logger, unsigned int level, const char* file,
+                   unsigned int line, std::string_view name,
+                   fmt::string_view format, fmt::format_args args) {
+  fmt::memory_buffer out;
+  fmt::format_to(fmt::appender{out}, "{}: ", name);
+  fmt::vformat_to(fmt::appender{out}, format, args);
+  out.push_back('\0');
+  logger.DoLog(level, file, line, out.data());
+}

cscore/src/main/native/cpp/Log.h

@@ -5,29 +5,71 @@
 #ifndef CSCORE_LOG_H_
 #define CSCORE_LOG_H_
 
+#include <string_view>
+
 #include <wpi/Logger.h>
 
-#define LOG(level, x) WPI_LOG(m_logger, level, x)
+namespace cs {
+
+void NamedLogV(wpi::Logger& logger, unsigned int level, const char* file,
+               unsigned int line, std::string_view name,
+               fmt::string_view format, fmt::format_args args);
+
+template <typename S, typename... Args>
+inline void NamedLog(wpi::Logger& logger, unsigned int level, const char* file,
+                     unsigned int line, std::string_view name, const S& format,
+                     Args&&... args) {
+  if (logger.HasLogger() && level >= logger.min_level()) {
+    NamedLogV(logger, level, file, line, name, format,
+              fmt::make_args_checked<Args...>(format, args...));
+  }
+}
+
+}  // namespace cs
+
+#define LOG(level, format, ...) WPI_LOG(m_logger, level, format, __VA_ARGS__)
 
 #undef ERROR
-#define ERROR(x) WPI_ERROR(m_logger, x)
-#define WARNING(x) WPI_WARNING(m_logger, x)
-#define INFO(x) WPI_INFO(m_logger, x)
+#define ERROR(format, ...) WPI_ERROR(m_logger, format, __VA_ARGS__)
+#define WARNING(format, ...) WPI_WARNING(m_logger, format, __VA_ARGS__)
+#define INFO(format, ...) WPI_INFO(m_logger, format, __VA_ARGS__)
 
-#define DEBUG0(x) WPI_DEBUG(m_logger, x)
-#define DEBUG1(x) WPI_DEBUG1(m_logger, x)
-#define DEBUG2(x) WPI_DEBUG2(m_logger, x)
-#define DEBUG3(x) WPI_DEBUG3(m_logger, x)
-#define DEBUG4(x) WPI_DEBUG4(m_logger, x)
+#define DEBUG0(format, ...) WPI_DEBUG(m_logger, format, __VA_ARGS__)
+#define DEBUG1(format, ...) WPI_DEBUG1(m_logger, format, __VA_ARGS__)
+#define DEBUG2(format, ...) WPI_DEBUG2(m_logger, format, __VA_ARGS__)
+#define DEBUG3(format, ...) WPI_DEBUG3(m_logger, format, __VA_ARGS__)
+#define DEBUG4(format, ...) WPI_DEBUG4(m_logger, format, __VA_ARGS__)
 
-#define SERROR(x) ERROR(GetName() << ": " << x)
-#define SWARNING(x) WARNING(GetName() << ": " << x)
-#define SINFO(x) INFO(GetName() << ": " << x)
+#define SLOG(level, format, ...)                                               \
+  NamedLog(m_logger, level, __FILE__, __LINE__, GetName(), FMT_STRING(format), \
+           __VA_ARGS__)
 
-#define SDEBUG(x) DEBUG0(GetName() << ": " << x)
-#define SDEBUG1(x) DEBUG1(GetName() << ": " << x)
-#define SDEBUG2(x) DEBUG2(GetName() << ": " << x)
-#define SDEBUG3(x) DEBUG3(GetName() << ": " << x)
-#define SDEBUG4(x) DEBUG4(GetName() << ": " << x)
+#define SERROR(format, ...) SLOG(::wpi::WPI_LOG_ERROR, format, __VA_ARGS__)
+#define SWARNING(format, ...) SLOG(::wpi::WPI_LOG_WARNING, format, __VA_ARGS__)
+#define SINFO(format, ...) SLOG(::wpi::WPI_LOG_INFO, format, __VA_ARGS__)
+
+#ifdef NDEBUG
+#define SDEBUG(format, ...) \
+  do {                      \
+  } while (0)
+#define SDEBUG1(format, ...) \
+  do {                       \
+  } while (0)
+#define SDEBUG2(format, ...) \
+  do {                       \
+  } while (0)
+#define SDEBUG3(format, ...) \
+  do {                       \
+  } while (0)
+#define SDEBUG4(format, ...) \
+  do {                       \
+  } while (0)
+#else
+#define SDEBUG(format, ...) SLOG(::wpi::WPI_LOG_DEBUG, format, __VA_ARGS__)
+#define SDEBUG1(format, ...) SLOG(::wpi::WPI_LOG_DEBUG1, format, __VA_ARGS__)
+#define SDEBUG2(format, ...) SLOG(::wpi::WPI_LOG_DEBUG2, format, __VA_ARGS__)
+#define SDEBUG3(format, ...) SLOG(::wpi::WPI_LOG_DEBUG3, format, __VA_ARGS__)
+#define SDEBUG4(format, ...) SLOG(::wpi::WPI_LOG_DEBUG4, format, __VA_ARGS__)
+#endif
 
 #endif  // CSCORE_LOG_H_

cscore/src/main/native/cpp/MjpegServerImpl.cpp

@@ -6,9 +6,12 @@
 
 #include <chrono>
 
+#include <fmt/format.h>
 #include <wpi/HttpUtil.h>
 #include <wpi/SmallString.h>
+#include <wpi/StringExtras.h>
 #include <wpi/TCPAcceptor.h>
+#include <wpi/fmt/raw_ostream.h>
 #include <wpi/raw_socket_istream.h>
 #include <wpi/raw_socket_ostream.h>
 
@@ -72,13 +75,13 @@ static const char* endRootPage = "</div></body></html>";
 
 class MjpegServerImpl::ConnThread : public wpi::SafeThread {
  public:
-  explicit ConnThread(const wpi::Twine& name, wpi::Logger& logger)
-      : m_name(name.str()), m_logger(logger) {}
+  explicit ConnThread(std::string_view name, wpi::Logger& logger)
+      : m_name(name), m_logger(logger) {}
 
   void Main() override;
 
   bool ProcessCommand(wpi::raw_ostream& os, SourceImpl& source,
-                      wpi::StringRef parameters, bool respond);
+                      std::string_view parameters, bool respond);
   void SendJSON(wpi::raw_ostream& os, SourceImpl& source, bool header);
   void SendHTMLHeadTitle(wpi::raw_ostream& os) const;
   void SendHTML(wpi::raw_ostream& os, SourceImpl& source, bool header);
@@ -99,7 +102,7 @@ class MjpegServerImpl::ConnThread : public wpi::SafeThread {
   std::string m_name;
   wpi::Logger& m_logger;
 
-  wpi::StringRef GetName() { return m_name; }
+  std::string_view GetName() { return m_name; }
 
   std::shared_ptr<SourceImpl> GetSource() {
     std::scoped_lock lock(m_mutex);
@@ -130,10 +133,9 @@ class MjpegServerImpl::ConnThread : public wpi::SafeThread {
 // Using cached pictures would lead to showing old/outdated pictures.
 // Many browsers seem to ignore, or at least not always obey, those headers.
 static void SendHeader(wpi::raw_ostream& os, int code,
-                       const wpi::Twine& codeText,
-                       const wpi::Twine& contentType,
-                       const wpi::Twine& extra = wpi::Twine{}) {
-  os << "HTTP/1.0 " << code << ' ' << codeText << "\r\n";
+                       std::string_view codeText, std::string_view contentType,
+                       std::string_view extra = {}) {
+  fmt::print(os, "HTTP/1.0 {} {}\r\n", code, codeText);
   os << "Connection: close\r\n"
         "Server: CameraServer/1.0\r\n"
         "Cache-Control: no-store, no-cache, must-revalidate, pre-check=0, "
@@ -142,10 +144,8 @@ static void SendHeader(wpi::raw_ostream& os, int code,
         "Expires: Mon, 3 Jan 2000 12:34:56 GMT\r\n";
   os << "Content-Type: " << contentType << "\r\n";
   os << "Access-Control-Allow-Origin: *\r\nAccess-Control-Allow-Methods: *\r\n";
-  wpi::SmallString<128> extraBuf;
-  wpi::StringRef extraStr = extra.toStringRef(extraBuf);
-  if (!extraStr.empty()) {
-    os << extraStr << "\r\n";
+  if (!extra.empty()) {
+    os << extra << "\r\n";
   }
   os << "\r\n";  // header ends with a blank line
 }
@@ -154,8 +154,8 @@ static void SendHeader(wpi::raw_ostream& os, int code,
 // @param code HTTP error code (e.g. 404)
 // @param message Additional message text
 static void SendError(wpi::raw_ostream& os, int code,
-                      const wpi::Twine& message) {
-  wpi::StringRef codeText, extra, baseMessage;
+                      std::string_view message) {
+  std::string_view codeText, extra, baseMessage;
   switch (code) {
     case 401:
       codeText = "Unauthorized";
@@ -195,66 +195,61 @@ static void SendError(wpi::raw_ostream& os, int code,
 // Perform a command specified by HTTP GET parameters.
 bool MjpegServerImpl::ConnThread::ProcessCommand(wpi::raw_ostream& os,
                                                  SourceImpl& source,
-                                                 wpi::StringRef parameters,
+                                                 std::string_view parameters,
                                                  bool respond) {
   wpi::SmallString<256> responseBuf;
   wpi::raw_svector_ostream response{responseBuf};
   // command format: param1=value1&param2=value2...
   while (!parameters.empty()) {
     // split out next param and value
-    wpi::StringRef rawParam, rawValue;
-    std::tie(rawParam, parameters) = parameters.split('&');
+    std::string_view rawParam, rawValue;
+    std::tie(rawParam, parameters) = wpi::split(parameters, '&');
     if (rawParam.empty()) {
       continue;  // ignore "&&"
     }
-    std::tie(rawParam, rawValue) = rawParam.split('=');
+    std::tie(rawParam, rawValue) = wpi::split(rawParam, '=');
     if (rawParam.empty() || rawValue.empty()) {
       continue;  // ignore "param="
     }
-    SDEBUG4("HTTP parameter \"" << rawParam << "\" value \"" << rawValue
-                                << "\"");
+    SDEBUG4("HTTP parameter \"{}\" value \"{}\"", rawParam, rawValue);
 
     // unescape param
     bool error = false;
     wpi::SmallString<64> paramBuf;
-    wpi::StringRef param = wpi::UnescapeURI(rawParam, paramBuf, &error);
+    std::string_view param = wpi::UnescapeURI(rawParam, paramBuf, &error);
     if (error) {
-      wpi::SmallString<128> error;
-      wpi::raw_svector_ostream oss{error};
-      oss << "could not unescape parameter \"" << rawParam << "\"";
-      SendError(os, 500, error.str());
-      SDEBUG(error.str());
+      auto estr = fmt::format("could not unescape parameter \"{}\"", rawParam);
+      SendError(os, 500, estr);
+      SDEBUG("{}", estr);
       return false;
     }
 
     // unescape value
     wpi::SmallString<64> valueBuf;
-    wpi::StringRef value = wpi::UnescapeURI(rawValue, valueBuf, &error);
+    std::string_view value = wpi::UnescapeURI(rawValue, valueBuf, &error);
     if (error) {
-      wpi::SmallString<128> error;
-      wpi::raw_svector_ostream oss{error};
-      oss << "could not unescape value \"" << rawValue << "\"";
-      SendError(os, 500, error.str());
-      SDEBUG(error.str());
+      auto estr = fmt::format("could not unescape value \"{}\"", rawValue);
+      SendError(os, 500, estr);
+      SDEBUG("{}", estr);
       return false;
     }
 
     // Handle resolution, compression, and FPS.  These are handled locally
     // rather than passed to the source.
     if (param == "resolution") {
-      wpi::StringRef widthStr, heightStr;
-      std::tie(widthStr, heightStr) = value.split('x');
-      int width, height;
-      if (widthStr.getAsInteger(10, width)) {
+      auto [widthStr, heightStr] = wpi::split(value, 'x');
+      int width = wpi::parse_integer<int>(widthStr, 10).value_or(-1);
+      int height = wpi::parse_integer<int>(heightStr, 10).value_or(-1);
+      if (width < 0) {
         response << param << ": \"width is not an integer\"\r\n";
-        SWARNING("HTTP parameter \"" << param << "\" width \"" << widthStr
-                                     << "\" is not an integer");
+        SWARNING("HTTP parameter \"{}\" width \"{}\" is not an integer", param,
+                 widthStr);
         continue;
       }
-      if (heightStr.getAsInteger(10, height)) {
+      if (height < 0) {
         response << param << ": \"height is not an integer\"\r\n";
-        SWARNING("HTTP parameter \"" << param << "\" height \"" << heightStr
-                                     << "\" is not an integer");
+        SWARNING("HTTP parameter \"{}\" height \"{}\" is not an integer", param,
+                 heightStr);
         continue;
       }
       m_width = width;
@@ -264,29 +259,25 @@ bool MjpegServerImpl::ConnThread::ProcessCommand(wpi::raw_ostream& os,
     }
 
     if (param == "fps") {
-      int fps;
-      if (value.getAsInteger(10, fps)) {
-        response << param << ": \"invalid integer\"\r\n";
-        SWARNING("HTTP parameter \"" << param << "\" value \"" << value
-                                     << "\" is not an integer");
-        continue;
-      } else {
-        m_fps = fps;
+      if (auto v = wpi::parse_integer<int>(value, 10)) {
+        m_fps = v.value();
         response << param << ": \"ok\"\r\n";
+      } else {
+        response << param << ": \"invalid integer\"\r\n";
+        SWARNING("HTTP parameter \"{}\" value \"{}\" is not an integer", param,
+                 value);
       }
       continue;
     }
 
     if (param == "compression") {
-      int compression;
-      if (value.getAsInteger(10, compression)) {
-        response << param << ": \"invalid integer\"\r\n";
-        SWARNING("HTTP parameter \"" << param << "\" value \"" << value
-                                     << "\" is not an integer");
-        continue;
-      } else {
-        m_compression = compression;
+      if (auto v = wpi::parse_integer<int>(value, 10)) {
+        m_compression = v.value();
         response << param << ": \"ok\"\r\n";
+      } else {
+        response << param << ": \"invalid integer\"\r\n";
+        SWARNING("HTTP parameter \"{}\" value \"{}\" is not an integer", param,
+                 value);
       }
       continue;
     }
@@ -300,7 +291,7 @@ bool MjpegServerImpl::ConnThread::ProcessCommand(wpi::raw_ostream& os,
     auto prop = source.GetPropertyIndex(param);
     if (!prop) {
       response << param << ": \"ignored\"\r\n";
-      SWARNING("ignoring HTTP parameter \"" << param << "\"");
+      SWARNING("ignoring HTTP parameter \"{}\"", param);
       continue;
     }
 
@@ -310,21 +301,20 @@ bool MjpegServerImpl::ConnThread::ProcessCommand(wpi::raw_ostream& os,
       case CS_PROP_BOOLEAN:
       case CS_PROP_INTEGER:
       case CS_PROP_ENUM: {
-        int val = 0;
-        if (value.getAsInteger(10, val)) {
-          response << param << ": \"invalid integer\"\r\n";
-          SWARNING("HTTP parameter \"" << param << "\" value \"" << value
-                                       << "\" is not an integer");
+        if (auto v = wpi::parse_integer<int>(value, 10)) {
+          fmt::print(response, "{}: {}\r\n", param, v.value());
+          SDEBUG4("HTTP parameter \"{}\" value {}", param, value);
+          source.SetProperty(prop, v.value(), &status);
         } else {
-          response << param << ": " << val << "\r\n";
-          SDEBUG4("HTTP parameter \"" << param << "\" value " << value);
-          source.SetProperty(prop, val, &status);
+          response << param << ": \"invalid integer\"\r\n";
+          SWARNING("HTTP parameter \"{}\" value \"{}\" is not an integer",
+                   param, value);
         }
         break;
       }
       case CS_PROP_STRING: {
         response << param << ": \"ok\"\r\n";
-        SDEBUG4("HTTP parameter \"" << param << "\" value \"" << value << "\"");
+        SDEBUG4("HTTP parameter \"{}\" value \"{}\"", param, value);
         source.SetStringProperty(prop, value, &status);
         break;
       }
@@ -362,17 +352,17 @@ void MjpegServerImpl::ConnThread::SendHTML(wpi::raw_ostream& os,
   for (auto prop : source.EnumerateProperties(properties_vec, &status)) {
     wpi::SmallString<128> name_buf;
     auto name = source.GetPropertyName(prop, name_buf, &status);
-    if (name.startswith("raw_")) {
+    if (wpi::starts_with(name, "raw_")) {
       continue;
     }
     auto kind = source.GetPropertyKind(prop);
-    os << "<p />"
-       << "<label for=\"" << name << "\">" << name << "</label>\n";
+    fmt::print(os, "<p /><label for=\"{0}\">{0}</label>\n", name);
     switch (kind) {
       case CS_PROP_BOOLEAN:
-        os << "<input id=\"" << name
-           << "\" type=\"checkbox\" onclick=\"update('" << name
-           << "', this.checked ? 1 : 0)\" ";
+        fmt::print(os,
+                   "<input id=\"{0}\" type=\"checkbox\" "
+                   "onclick=\"update('{0}', this.checked ? 1 : 0)\" ",
+                   name);
         if (source.GetProperty(prop, &status) != 0) {
           os << "checked />\n";
         } else {
@@ -384,12 +374,13 @@ void MjpegServerImpl::ConnThread::SendHTML(wpi::raw_ostream& os,
         auto min = source.GetPropertyMin(prop, &status);
         auto max = source.GetPropertyMax(prop, &status);
         auto step = source.GetPropertyStep(prop, &status);
-        os << "<input type=\"range\" min=\"" << min << "\" max=\"" << max
-           << "\" value=\"" << valI << "\" id=\"" << name << "\" step=\""
-           << step << "\" oninput=\"updateInt('#" << name << "op', '" << name
-           << "', value)\" />\n";
-        os << "<output for=\"" << name << "\" id=\"" << name << "op\">" << valI
-           << "</output>\n";
+        fmt::print(os,
+                   "<input type=\"range\" min=\"{1}\" max=\"{2}\" "
+                   "value=\"{3}\" id=\"{0}\" step=\"{4}\" "
+                   "oninput=\"updateInt('#{0}op', '{0}', value)\" />\n",
+                   name, min, max, valI, step);
+        fmt::print(os, "<output for=\"{0}\" id=\"{0}op\">{1}</output>\n", name,
+                   valI);
         break;
       }
       case CS_PROP_ENUM: {
@@ -404,26 +395,30 @@ void MjpegServerImpl::ConnThread::SendHTML(wpi::raw_ostream& os,
           // replace any non-printable characters in name with spaces
           wpi::SmallString<128> ch_name;
           for (char ch : *choice) {
-            ch_name.push_back(std::isprint(ch) ? ch : ' ');
+            ch_name.push_back(wpi::isPrint(ch) ? ch : ' ');
           }
-          os << "<input id=\"" << name << j << "\" type=\"radio\" name=\""
-             << name << "\" value=\"" << ch_name << "\" onclick=\"update('"
-             << name << "', " << j << ")\"";
+          fmt::print(os,
+                     "<input id=\"{0}{1}\" type=\"radio\" name=\"{0}\" "
+                     "value=\"{2}\" onclick=\"update('{0}', {1})\"",
+                     name, j, ch_name);
           if (j == valE) {
             os << " checked";
           }
-          os << " /><label for=\"" << name << j << "\">" << ch_name
-             << "</label>\n";
+          fmt::print(os, " /><label for=\"{}{}\">{}</label>\n", name, j,
+                     ch_name);
         }
         break;
       }
       case CS_PROP_STRING: {
         wpi::SmallString<128> strval_buf;
-        os << "<input type=\"text\" id=\"" << name << "box\" name=\"" << name
-           << "\" value=\""
-           << source.GetStringProperty(prop, strval_buf, &status) << "\" />\n";
-        os << "<input type=\"button\" value =\"Submit\" onclick=\"update('"
-           << name << "', " << name << "box.value)\" />\n";
+        fmt::print(os,
+                   "<input type=\"text\" id=\"{0}box\" name=\"{0}\" "
+                   "value=\"{1}\" />\n",
+                   name, source.GetStringProperty(prop, strval_buf, &status));
+        fmt::print(os,
+                   "<input type=\"button\" value =\"Submit\" "
+                   "onclick=\"update('{0}', {0}box.value)\" />\n",
+                   name);
         break;
       }
       default:
@@ -469,10 +464,8 @@ void MjpegServerImpl::ConnThread::SendHTML(wpi::raw_ostream& os,
         os << "unknown";
         break;
     }
-    os << "</td><td>" << mode.width;
-    os << "</td><td>" << mode.height;
-    os << "</td><td>" << mode.fps;
-    os << "</td></tr>";
+    fmt::print(os, "</td><td>{}</td><td>{}</td><td>{}</td></tr>", mode.width,
+               mode.height, mode.fps);
   }
   os << "</table>\n";
   os << endRootPage << "\r\n";
@@ -500,20 +493,21 @@ void MjpegServerImpl::ConnThread::SendJSON(wpi::raw_ostream& os,
     wpi::SmallString<128> name_buf;
     auto name = source.GetPropertyName(prop, name_buf, &status);
     auto kind = source.GetPropertyKind(prop);
-    os << "\n\"name\": \"" << name << '"';
-    os << ",\n\"id\": \"" << prop << '"';
-    os << ",\n\"type\": \"" << kind << '"';
-    os << ",\n\"min\": \"" << source.GetPropertyMin(prop, &status) << '"';
-    os << ",\n\"max\": \"" << source.GetPropertyMax(prop, &status) << '"';
-    os << ",\n\"step\": \"" << source.GetPropertyStep(prop, &status) << '"';
-    os << ",\n\"default\": \"" << source.GetPropertyDefault(prop, &status)
-       << '"';
+    fmt::print(os, "\n\"name\": \"{}\"", name);
+    fmt::print(os, ",\n\"id\": \"{}\"", prop);
+    fmt::print(os, ",\n\"type\": \"{}\"", kind);
+    fmt::print(os, ",\n\"min\": \"{}\"", source.GetPropertyMin(prop, &status));
+    fmt::print(os, ",\n\"max\": \"{}\"", source.GetPropertyMax(prop, &status));
+    fmt::print(os, ",\n\"step\": \"{}\"",
+               source.GetPropertyStep(prop, &status));
+    fmt::print(os, ",\n\"default\": \"{}\"",
+               source.GetPropertyDefault(prop, &status));
     os << ",\n\"value\": \"";
     switch (kind) {
       case CS_PROP_BOOLEAN:
       case CS_PROP_INTEGER:
       case CS_PROP_ENUM:
-        os << source.GetProperty(prop, &status);
+        fmt::print(os, "{}", source.GetProperty(prop, &status));
         break;
       case CS_PROP_STRING: {
         wpi::SmallString<128> strval_buf;
@@ -543,7 +537,7 @@ void MjpegServerImpl::ConnThread::SendJSON(wpi::raw_ostream& os,
         for (char ch : *choice) {
           ch_name.push_back(std::isprint(ch) ? ch : ' ');
         }
-        os << '"' << j << "\": \"" << ch_name << '"';
+        fmt::print(os, "\"{}\": \"{}\"", j, ch_name);
       }
       os << "}\n";
     }
@@ -579,29 +573,26 @@ void MjpegServerImpl::ConnThread::SendJSON(wpi::raw_ostream& os,
         os << "unknown";
         break;
     }
-    os << "\",\n\"width\": \"" << mode.width << '"';
-    os << ",\n\"height\": \"" << mode.height << '"';
-    os << ",\n\"fps\": \"" << mode.fps << '"';
+    fmt::print(os, "\",\n\"width\": \"{}\"", mode.width);
+    fmt::print(os, ",\n\"height\": \"{}\"", mode.height);
+    fmt::print(os, ",\n\"fps\": \"{}\"", mode.fps);
     os << '}';
   }
   os << "\n]\n}\n";
   os.flush();
 }
 
-MjpegServerImpl::MjpegServerImpl(const wpi::Twine& name, wpi::Logger& logger,
+MjpegServerImpl::MjpegServerImpl(std::string_view name, wpi::Logger& logger,
                                  Notifier& notifier, Telemetry& telemetry,
-                                 const wpi::Twine& listenAddress, int port,
+                                 std::string_view listenAddress, int port,
                                  std::unique_ptr<wpi::NetworkAcceptor> acceptor)
     : SinkImpl{name, logger, notifier, telemetry},
-      m_listenAddress(listenAddress.str()),
+      m_listenAddress(listenAddress),
       m_port(port),
       m_acceptor{std::move(acceptor)} {
   m_active = true;
 
-  wpi::SmallString<128> descBuf;
-  wpi::raw_svector_ostream desc{descBuf};
-  desc << "HTTP Server on port " << port;
-  SetDescription(desc.str());
+  SetDescription(fmt::format("HTTP Server on port {}", port));
 
   // Create properties
   m_widthProp = CreateProperty("width", [] {
@@ -659,7 +650,7 @@ void MjpegServerImpl::Stop() {
 // Send HTTP response and a stream of JPG-frames
 void MjpegServerImpl::ConnThread::SendStream(wpi::raw_socket_ostream& os) {
   if (m_noStreaming) {
-    SERROR("Too many simultaneous client streams");
+    SERROR("{}", "Too many simultaneous client streams");
     SendError(os, 503, "Too many simultaneous streams");
     return;
   }
@@ -672,7 +663,7 @@ void MjpegServerImpl::ConnThread::SendStream(wpi::raw_socket_ostream& os) {
   SendHeader(oss, 200, "OK", "multipart/x-mixed-replace;boundary=" BOUNDARY);
   os << oss.str();
 
-  SDEBUG("Headers send, sending stream now");
+  SDEBUG("{}", "Headers send, sending stream now");
 
   Frame::Time lastFrameTime = 0;
   Frame::Time timePerFrame = 0;
@@ -694,7 +685,7 @@ void MjpegServerImpl::ConnThread::SendStream(wpi::raw_socket_ostream& os) {
       std::this_thread::sleep_for(std::chrono::milliseconds(200));
       continue;
     }
-    SDEBUG4("waiting for frame");
+    SDEBUG4("{}", "waiting for frame");
     Frame frame = source->GetNextFrame(0.225);  // blocks
     if (!m_active) {
       break;
@@ -757,7 +748,7 @@ void MjpegServerImpl::ConnThread::SendStream(wpi::raw_socket_ostream& os) {
         continue;
     }
 
-    SDEBUG4("sending frame size=" << size << " addDHT=" << addDHT);
+    SDEBUG4("sending frame size={} addDHT={}", size, addDHT);
 
     // print the individual mimetype and the length
     // sending the content-length fixes random stream disruption observed
@@ -766,18 +757,18 @@ void MjpegServerImpl::ConnThread::SendStream(wpi::raw_socket_ostream& os) {
     double timestamp = lastFrameTime / 1000000.0;
     header.clear();
     oss << "\r\n--" BOUNDARY "\r\n"
-        << "Content-Type: image/jpeg\r\n"
-        << "Content-Length: " << size << "\r\n"
-        << "X-Timestamp: " << timestamp << "\r\n"
-        << "\r\n";
+        << "Content-Type: image/jpeg\r\n";
+    fmt::print(oss, "Content-Length: {}\r\n", size);
+    fmt::print(oss, "X-Timestamp: {}\r\n", timestamp);
+    oss << "\r\n";
     os << oss.str();
     if (addDHT) {
       // Insert DHT data immediately before SOF
-      os << wpi::StringRef(data, locSOF);
+      os << std::string_view(data, locSOF);
       os << JpegGetDHT();
-      os << wpi::StringRef(data + locSOF, image->size() - locSOF);
+      os << std::string_view(data + locSOF, image->size() - locSOF);
     } else {
-      os << wpi::StringRef(data, size);
+      os << std::string_view(data, size);
     }
     // os.flush();
   }
@@ -790,48 +781,50 @@ void MjpegServerImpl::ConnThread::ProcessRequest() {
 
   // Read the request string from the stream
   wpi::SmallString<128> reqBuf;
-  wpi::StringRef req = is.getline(reqBuf, 4096);
+  std::string_view req = is.getline(reqBuf, 4096);
   if (is.has_error()) {
-    SDEBUG("error getting request string");
+    SDEBUG("{}", "error getting request string");
     return;
   }
 
   enum { kCommand, kStream, kGetSettings, kGetSourceConfig, kRootPage } kind;
-  wpi::StringRef parameters;
+  std::string_view parameters;
   size_t pos;
 
-  SDEBUG("HTTP request: '" << req << "'\n");
+  SDEBUG("HTTP request: '{}'\n", req);
 
   // Determine request kind.  Most of these are for mjpgstreamer
   // compatibility, others are for Axis camera compatibility.
-  if ((pos = req.find("POST /stream")) != wpi::StringRef::npos) {
+  if ((pos = req.find("POST /stream")) != std::string_view::npos) {
     kind = kStream;
     parameters = req.substr(req.find('?', pos + 12)).substr(1);
-  } else if ((pos = req.find("GET /?action=stream")) != wpi::StringRef::npos) {
+  } else if ((pos = req.find("GET /?action=stream")) !=
+             std::string_view::npos) {
     kind = kStream;
     parameters = req.substr(req.find('&', pos + 19)).substr(1);
-  } else if ((pos = req.find("GET /stream.mjpg")) != wpi::StringRef::npos) {
+  } else if ((pos = req.find("GET /stream.mjpg")) != std::string_view::npos) {
     kind = kStream;
     parameters = req.substr(req.find('?', pos + 16)).substr(1);
-  } else if (req.find("GET /settings") != wpi::StringRef::npos &&
-             req.find(".json") != wpi::StringRef::npos) {
+  } else if (req.find("GET /settings") != std::string_view::npos &&
+             req.find(".json") != std::string_view::npos) {
     kind = kGetSettings;
-  } else if (req.find("GET /config") != wpi::StringRef::npos &&
-             req.find(".json") != wpi::StringRef::npos) {
+  } else if (req.find("GET /config") != std::string_view::npos &&
+             req.find(".json") != std::string_view::npos) {
     kind = kGetSourceConfig;
-  } else if (req.find("GET /input") != wpi::StringRef::npos &&
-             req.find(".json") != wpi::StringRef::npos) {
+  } else if (req.find("GET /input") != std::string_view::npos &&
+             req.find(".json") != std::string_view::npos) {
     kind = kGetSettings;
-  } else if (req.find("GET /output") != wpi::StringRef::npos &&
-             req.find(".json") != wpi::StringRef::npos) {
+  } else if (req.find("GET /output") != std::string_view::npos &&
+             req.find(".json") != std::string_view::npos) {
     kind = kGetSettings;
-  } else if ((pos = req.find("GET /?action=command")) != wpi::StringRef::npos) {
+  } else if ((pos = req.find("GET /?action=command")) !=
+             std::string_view::npos) {
     kind = kCommand;
     parameters = req.substr(req.find('&', pos + 20)).substr(1);
-  } else if (req.find("GET / ") != wpi::StringRef::npos || req == "GET /\n") {
+  } else if (req.find("GET / ") != std::string_view::npos || req == "GET /\n") {
     kind = kRootPage;
   } else {
-    SDEBUG("HTTP request resource not found");
+    SDEBUG("{}", "HTTP request resource not found");
     SendError(os, 404, "Resource not found");
     return;
   }
@@ -841,13 +834,13 @@ void MjpegServerImpl::ConnThread::ProcessRequest() {
       "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_"
       "-=&1234567890%./");
   parameters = parameters.substr(0, pos);
-  SDEBUG("command parameters: \"" << parameters << "\"");
+  SDEBUG("command parameters: \"{}\"", parameters);
 
   // Read the rest of the HTTP request.
   // The end of the request is marked by a single, empty line
   wpi::SmallString<128> lineBuf;
   for (;;) {
-    if (is.getline(lineBuf, 4096).startswith("\n")) {
+    if (wpi::starts_with(is.getline(lineBuf, 4096), "\n")) {
       break;
     }
     if (is.has_error()) {
@@ -859,7 +852,7 @@ void MjpegServerImpl::ConnThread::ProcessRequest() {
   switch (kind) {
     case kStream:
       if (auto source = GetSource()) {
-        SDEBUG("request for stream " << source->GetName());
+        SDEBUG("request for stream {}", source->GetName());
         if (!ProcessCommand(os, *source, parameters, false)) {
           return;
         }
@@ -873,11 +866,11 @@ void MjpegServerImpl::ConnThread::ProcessRequest() {
         SendHeader(os, 200, "OK", "text/plain");
         os << "Ignored due to no connected source."
            << "\r\n";
-        SDEBUG("Ignored due to no connected source.");
+        SDEBUG("{}", "Ignored due to no connected source.");
       }
       break;
     case kGetSettings:
-      SDEBUG("request for JSON file");
+      SDEBUG("{}", "request for JSON file");
       if (auto source = GetSource()) {
         SendJSON(os, *source, true);
       } else {
@@ -885,7 +878,7 @@ void MjpegServerImpl::ConnThread::ProcessRequest() {
       }
       break;
     case kGetSourceConfig:
-      SDEBUG("request for JSON file");
+      SDEBUG("{}", "request for JSON file");
       if (auto source = GetSource()) {
         SendHeader(os, 200, "OK", "application/json");
         CS_Status status = CS_OK;
@@ -896,7 +889,7 @@ void MjpegServerImpl::ConnThread::ProcessRequest() {
       }
       break;
     case kRootPage:
-      SDEBUG("request for root page");
+      SDEBUG("{}", "request for root page");
       SendHeader(os, 200, "OK", "text/html");
       if (auto source = GetSource()) {
         SendHTML(os, *source, false);
@@ -907,7 +900,7 @@ void MjpegServerImpl::ConnThread::ProcessRequest() {
       break;
   }
 
-  SDEBUG("leaving HTTP client thread");
+  SDEBUG("{}", "leaving HTTP client thread");
 }
 
 // worker thread for clients that connected to this server
@@ -934,7 +927,7 @@ void MjpegServerImpl::ServerThreadMain() {
     return;
   }
 
-  SDEBUG("waiting for clients to connect");
+  SDEBUG("{}", "waiting for clients to connect");
   while (m_active) {
     auto stream = m_acceptor->accept();
     if (!stream) {
@@ -945,7 +938,7 @@ void MjpegServerImpl::ServerThreadMain() {
       return;
     }
 
-    SDEBUG("client connection from " << stream->getPeerIP());
+    SDEBUG("client connection from {}", stream->getPeerIP());
 
     auto source = GetSource();
 
@@ -984,7 +977,7 @@ void MjpegServerImpl::ServerThreadMain() {
     thr->m_cond.notify_one();
   }
 
-  SDEBUG("leaving server thread");
+  SDEBUG("{}", "leaving server thread");
 }
 
 void MjpegServerImpl::SetSourceImpl(std::shared_ptr<SourceImpl> source) {
@@ -1007,19 +1000,15 @@ void MjpegServerImpl::SetSourceImpl(std::shared_ptr<SourceImpl> source) {
 
 namespace cs {
 
-CS_Sink CreateMjpegServer(const wpi::Twine& name,
-                          const wpi::Twine& listenAddress, int port,
-                          CS_Status* status) {
+CS_Sink CreateMjpegServer(std::string_view name, std::string_view listenAddress,
+                          int port, CS_Status* status) {
   auto& inst = Instance::GetInstance();
-  wpi::SmallString<128> listenAddressBuf;
   return inst.CreateSink(
       CS_SINK_MJPEG,
       std::make_shared<MjpegServerImpl>(
           name, inst.logger, inst.notifier, inst.telemetry, listenAddress, port,
-          std::unique_ptr<wpi::NetworkAcceptor>(new wpi::TCPAcceptor(
-              port,
-              listenAddress.toNullTerminatedStringRef(listenAddressBuf).data(),
-              inst.logger))));
+          std::unique_ptr<wpi::NetworkAcceptor>(
+              new wpi::TCPAcceptor(port, listenAddress, inst.logger))));
 }
 
 std::string GetMjpegServerListenAddress(CS_Sink sink, CS_Status* status) {

cscore/src/main/native/cpp/MjpegServerImpl.h

@@ -8,6 +8,7 @@
 #include <atomic>
 #include <memory>
 #include <string>
+#include <string_view>
 #include <thread>
 #include <vector>
 
@@ -15,7 +16,6 @@
 #include <wpi/NetworkStream.h>
 #include <wpi/SafeThread.h>
 #include <wpi/SmallVector.h>
-#include <wpi/Twine.h>
 #include <wpi/raw_istream.h>
 #include <wpi/raw_ostream.h>
 #include <wpi/raw_socket_ostream.h>
@@ -28,9 +28,9 @@ class SourceImpl;
 
 class MjpegServerImpl : public SinkImpl {
  public:
-  MjpegServerImpl(const wpi::Twine& name, wpi::Logger& logger,
+  MjpegServerImpl(std::string_view name, wpi::Logger& logger,
                   Notifier& notifier, Telemetry& telemetry,
-                  const wpi::Twine& listenAddress, int port,
+                  std::string_view listenAddress, int port,
                   std::unique_ptr<wpi::NetworkAcceptor> acceptor);
   ~MjpegServerImpl() override;
 

cscore/src/main/native/cpp/Notifier.cpp

@@ -15,170 +15,26 @@
 
 using namespace cs;
 
-bool Notifier::s_destroyed = false;
+Notifier::Notifier() {}
 
-namespace {
-// Vector which provides an integrated freelist for removal and reuse of
-// individual elements.
-template <typename T>
-class UidVector {
- public:
-  using size_type = typename std::vector<T>::size_type;
-
-  size_type size() const { return m_vector.size(); }
-  T& operator[](size_type i) { return m_vector[i]; }
-  const T& operator[](size_type i) const { return m_vector[i]; }
-
-  // Add a new T to the vector.  If there are elements on the freelist,
-  // reuses the last one; otherwise adds to the end of the vector.
-  // Returns the resulting element index (+1).
-  template <class... Args>
-  unsigned int emplace_back(Args&&... args) {
-    unsigned int uid;
-    if (m_free.empty()) {
-      uid = m_vector.size();
-      m_vector.emplace_back(std::forward<Args>(args)...);
-    } else {
-      uid = m_free.back();
-      m_free.pop_back();
-      m_vector[uid] = T(std::forward<Args>(args)...);
-    }
-    return uid + 1;
-  }
-
-  // Removes the identified element by replacing it with a default-constructed
-  // one.  The element is added to the freelist for later reuse.
-  void erase(unsigned int uid) {
-    --uid;
-    if (uid >= m_vector.size() || !m_vector[uid]) {
-      return;
-    }
-    m_free.push_back(uid);
-    m_vector[uid] = T();
-  }
-
- private:
-  std::vector<T> m_vector;
-  std::vector<unsigned int> m_free;
-};
-
-}  // namespace
-
-class Notifier::Thread : public wpi::SafeThread {
- public:
-  Thread(std::function<void()> on_start, std::function<void()> on_exit)
-      : m_on_start(std::move(on_start)), m_on_exit(std::move(on_exit)) {}
-
-  void Main() override;
-
-  struct Listener {
-    Listener() = default;
-    Listener(std::function<void(const RawEvent& event)> callback_,
-             int eventMask_)
-        : callback(std::move(callback_)), eventMask(eventMask_) {}
-
-    explicit operator bool() const { return static_cast<bool>(callback); }
-
-    std::string prefix;
-    std::function<void(const RawEvent& event)> callback;
-    int eventMask;
-  };
-  UidVector<Listener> m_listeners;
-
-  std::queue<RawEvent> m_notifications;
-
-  std::function<void()> m_on_start;
-  std::function<void()> m_on_exit;
-};
-
-Notifier::Notifier() {
-  s_destroyed = false;
-}
-
-Notifier::~Notifier() {
-  s_destroyed = true;
-}
+Notifier::~Notifier() {}
 
 void Notifier::Start() {
-  m_owner.Start(m_on_start, m_on_exit);
+  DoStart();
 }
 
-void Notifier::Stop() {
-  m_owner.Stop();
+unsigned int Notifier::Add(std::function<void(const RawEvent& event)> callback,
+                           int eventMask) {
+  return DoAdd(callback, eventMask);
 }
 
-void Notifier::Thread::Main() {
-  if (m_on_start) {
-    m_on_start();
-  }
-
-  std::unique_lock lock(m_mutex);
-  while (m_active) {
-    while (m_notifications.empty()) {
-      m_cond.wait(lock);
-      if (!m_active) {
-        goto done;
-      }
-    }
-
-    while (!m_notifications.empty()) {
-      if (!m_active) {
-        goto done;
-      }
-      auto item = std::move(m_notifications.front());
-      m_notifications.pop();
-
-      // Use index because iterator might get invalidated.
-      for (size_t i = 0; i < m_listeners.size(); ++i) {
-        if (!m_listeners[i]) {
-          continue;  // removed
-        }
-
-        // Event type must be within requested set for this listener.
-        if ((item.kind & m_listeners[i].eventMask) == 0) {
-          continue;
-        }
-
-        // make a copy of the callback so we can safely release the mutex
-        auto callback = m_listeners[i].callback;
-
-        // Don't hold mutex during callback execution!
-        lock.unlock();
-        callback(item);
-        lock.lock();
-      }
-    }
-  }
-
-done:
-  if (m_on_exit) {
-    m_on_exit();
-  }
+unsigned int Notifier::AddPolled(unsigned int pollerUid, int eventMask) {
+  return DoAdd(pollerUid, eventMask);
 }
 
-int Notifier::AddListener(std::function<void(const RawEvent& event)> callback,
-                          int eventMask) {
-  Start();
-  auto thr = m_owner.GetThread();
-  return thr->m_listeners.emplace_back(callback, eventMask);
-}
-
-void Notifier::RemoveListener(int uid) {
-  auto thr = m_owner.GetThread();
-  if (!thr) {
-    return;
-  }
-  thr->m_listeners.erase(uid);
-}
-
-void Notifier::NotifySource(const wpi::Twine& name, CS_Source source,
+void Notifier::NotifySource(std::string_view name, CS_Source source,
                             CS_EventKind kind) {
-  auto thr = m_owner.GetThread();
-  if (!thr) {
-    return;
-  }
-  thr->m_notifications.emplace(name, source, static_cast<RawEvent::Kind>(kind));
-  thr->m_cond.notify_one();
+  Send(UINT_MAX, name, source, static_cast<RawEvent::Kind>(kind));
 }
 
 void Notifier::NotifySource(const SourceImpl& source, CS_EventKind kind) {
@@ -188,44 +44,24 @@ void Notifier::NotifySource(const SourceImpl& source, CS_EventKind kind) {
 
 void Notifier::NotifySourceVideoMode(const SourceImpl& source,
                                      const VideoMode& mode) {
-  auto thr = m_owner.GetThread();
-  if (!thr) {
-    return;
-  }
-
   auto handleData = Instance::GetInstance().FindSource(source);
-
-  thr->m_notifications.emplace(source.GetName(), handleData.first, mode);
-  thr->m_cond.notify_one();
+  Send(UINT_MAX, source.GetName(), handleData.first, mode);
 }
 
 void Notifier::NotifySourceProperty(const SourceImpl& source, CS_EventKind kind,
-                                    const wpi::Twine& propertyName,
-                                    int property, CS_PropertyKind propertyKind,
-                                    int value, const wpi::Twine& valueStr) {
-  auto thr = m_owner.GetThread();
-  if (!thr) {
-    return;
-  }
-
+                                    std::string_view propertyName, int property,
+                                    CS_PropertyKind propertyKind, int value,
+                                    std::string_view valueStr) {
   auto handleData = Instance::GetInstance().FindSource(source);
-
-  thr->m_notifications.emplace(
-      propertyName, handleData.first, static_cast<RawEvent::Kind>(kind),
-      Handle{handleData.first, property, Handle::kProperty}, propertyKind,
-      value, valueStr);
-  thr->m_cond.notify_one();
+  Send(UINT_MAX, propertyName, handleData.first,
+       static_cast<RawEvent::Kind>(kind),
+       Handle{handleData.first, property, Handle::kProperty}, propertyKind,
+       value, valueStr);
 }
 
-void Notifier::NotifySink(const wpi::Twine& name, CS_Sink sink,
+void Notifier::NotifySink(std::string_view name, CS_Sink sink,
                           CS_EventKind kind) {
-  auto thr = m_owner.GetThread();
-  if (!thr) {
-    return;
-  }
-
-  thr->m_notifications.emplace(name, sink, static_cast<RawEvent::Kind>(kind));
-  thr->m_cond.notify_one();
+  Send(UINT_MAX, name, sink, static_cast<RawEvent::Kind>(kind));
 }
 
 void Notifier::NotifySink(const SinkImpl& sink, CS_EventKind kind) {
@@ -233,54 +69,32 @@ void Notifier::NotifySink(const SinkImpl& sink, CS_EventKind kind) {
   NotifySink(sink.GetName(), handleData.first, kind);
 }
 
-void Notifier::NotifySinkSourceChanged(const wpi::Twine& name, CS_Sink sink,
+void Notifier::NotifySinkSourceChanged(std::string_view name, CS_Sink sink,
                                        CS_Source source) {
-  auto thr = m_owner.GetThread();
-  if (!thr) {
-    return;
-  }
-
   RawEvent event{name, sink, RawEvent::kSinkSourceChanged};
   event.sourceHandle = source;
-
-  thr->m_notifications.emplace(std::move(event));
-  thr->m_cond.notify_one();
+  Send(UINT_MAX, std::move(event));
 }
 
 void Notifier::NotifySinkProperty(const SinkImpl& sink, CS_EventKind kind,
-                                  const wpi::Twine& propertyName, int property,
+                                  std::string_view propertyName, int property,
                                   CS_PropertyKind propertyKind, int value,
-                                  const wpi::Twine& valueStr) {
-  auto thr = m_owner.GetThread();
-  if (!thr) {
-    return;
-  }
-
+                                  std::string_view valueStr) {
   auto handleData = Instance::GetInstance().FindSink(sink);
-
-  thr->m_notifications.emplace(
-      propertyName, handleData.first, static_cast<RawEvent::Kind>(kind),
-      Handle{handleData.first, property, Handle::kSinkProperty}, propertyKind,
-      value, valueStr);
-  thr->m_cond.notify_one();
+  Send(UINT_MAX, propertyName, handleData.first,
+       static_cast<RawEvent::Kind>(kind),
+       Handle{handleData.first, property, Handle::kSinkProperty}, propertyKind,
+       value, valueStr);
 }
 
 void Notifier::NotifyNetworkInterfacesChanged() {
-  auto thr = m_owner.GetThread();
-  if (!thr) {
-    return;
-  }
-
-  thr->m_notifications.emplace(RawEvent::kNetworkInterfacesChanged);
-  thr->m_cond.notify_one();
+  Send(UINT_MAX, RawEvent::kNetworkInterfacesChanged);
 }
 
 void Notifier::NotifyTelemetryUpdated() {
-  auto thr = m_owner.GetThread();
-  if (!thr) {
-    return;
-  }
-
-  thr->m_notifications.emplace(RawEvent::kTelemetryUpdated);
-  thr->m_cond.notify_one();
+  Send(UINT_MAX, RawEvent::kTelemetryUpdated);
+}
+
+void Notifier::NotifyUsbCamerasChanged() {
+  Send(UINT_MAX, RawEvent::kUsbCamerasChanged);
 }

cscore/src/main/native/cpp/Notifier.h

@@ -6,9 +6,11 @@
 #define CSCORE_NOTIFIER_H_
 
 #include <functional>
+#include <utility>
 
-#include <wpi/SafeThread.h>
+#include <wpi/CallbackManager.h>
 
+#include "Handle.h"
 #include "cscore_cpp.h"
 
 namespace cs {
@@ -16,7 +18,40 @@ namespace cs {
 class SinkImpl;
 class SourceImpl;
 
-class Notifier {
+namespace impl {
+
+struct ListenerData : public wpi::CallbackListenerData<
+                          std::function<void(const RawEvent& event)>> {
+  ListenerData() = default;
+  ListenerData(std::function<void(const RawEvent& event)> callback_,
+               int eventMask_)
+      : CallbackListenerData(std::move(callback_)), eventMask(eventMask_) {}
+  ListenerData(unsigned int pollerUid_, int eventMask_)
+      : CallbackListenerData(pollerUid_), eventMask(eventMask_) {}
+
+  int eventMask;
+};
+
+class NotifierThread
+    : public wpi::CallbackThread<NotifierThread, RawEvent, ListenerData> {
+ public:
+  bool Matches(const ListenerData& /*listener*/, const RawEvent& /*data*/) {
+    return true;
+  }
+
+  void SetListener(RawEvent* data, unsigned int listener_uid) {
+    data->listener = Handle(listener_uid, Handle::kListener);
+  }
+
+  void DoCallback(std::function<void(const RawEvent& event)> callback,
+                  const RawEvent& data) {
+    callback(data);
+  }
+};
+
+}  // namespace impl
+
+class Notifier : public wpi::CallbackManager<Notifier, impl::NotifierThread> {
   friend class NotifierTest;
 
  public:
@@ -24,44 +59,30 @@ class Notifier {
   ~Notifier();
 
   void Start();
-  void Stop();
 
-  static bool destroyed() { return s_destroyed; }
-
-  void SetOnStart(std::function<void()> on_start) { m_on_start = on_start; }
-  void SetOnExit(std::function<void()> on_exit) { m_on_exit = on_exit; }
-
-  int AddListener(std::function<void(const RawEvent& event)> callback,
-                  int eventMask);
-  void RemoveListener(int uid);
+  unsigned int Add(std::function<void(const RawEvent& event)> callback,
+                   int eventMask);
+  unsigned int AddPolled(unsigned int pollerUid, int eventMask);
 
   // Notification events
-  void NotifySource(const wpi::Twine& name, CS_Source source,
-                    CS_EventKind kind);
+  void NotifySource(std::string_view name, CS_Source source, CS_EventKind kind);
   void NotifySource(const SourceImpl& source, CS_EventKind kind);
   void NotifySourceVideoMode(const SourceImpl& source, const VideoMode& mode);
   void NotifySourceProperty(const SourceImpl& source, CS_EventKind kind,
-                            const wpi::Twine& propertyName, int property,
+                            std::string_view propertyName, int property,
                             CS_PropertyKind propertyKind, int value,
-                            const wpi::Twine& valueStr);
-  void NotifySink(const wpi::Twine& name, CS_Sink sink, CS_EventKind kind);
+                            std::string_view valueStr);
+  void NotifySink(std::string_view name, CS_Sink sink, CS_EventKind kind);
   void NotifySink(const SinkImpl& sink, CS_EventKind kind);
-  void NotifySinkSourceChanged(const wpi::Twine& name, CS_Sink sink,
+  void NotifySinkSourceChanged(std::string_view name, CS_Sink sink,
                                CS_Source source);
   void NotifySinkProperty(const SinkImpl& sink, CS_EventKind kind,
-                          const wpi::Twine& propertyName, int property,
+                          std::string_view propertyName, int property,
                           CS_PropertyKind propertyKind, int value,
-                          const wpi::Twine& valueStr);
+                          std::string_view valueStr);
   void NotifyNetworkInterfacesChanged();
   void NotifyTelemetryUpdated();
-
- private:
-  class Thread;
-  wpi::SafeThreadOwner<Thread> m_owner;
-
-  std::function<void()> m_on_start;
-  std::function<void()> m_on_exit;
-  static bool s_destroyed;
+  void NotifyUsbCamerasChanged();
 };
 
 }  // namespace cs

cscore/src/main/native/cpp/PropertyContainer.cpp

@@ -11,15 +11,14 @@
 
 using namespace cs;
 
-int PropertyContainer::GetPropertyIndex(const wpi::Twine& name) const {
+int PropertyContainer::GetPropertyIndex(std::string_view name) const {
   // We can't fail, so instead we create a new index if caching fails.
   CS_Status status = 0;
   if (!m_properties_cached) {
     CacheProperties(&status);
   }
   std::scoped_lock lock(m_mutex);
-  wpi::SmallVector<char, 64> nameBuf;
-  int& ndx = m_properties[name.toStringRef(nameBuf)];
+  int& ndx = m_properties[name];
   if (ndx == 0) {
     // create a new index
     ndx = m_propertyData.size() + 1;
@@ -28,7 +27,7 @@ int PropertyContainer::GetPropertyIndex(const wpi::Twine& name) const {
   return ndx;
 }
 
-wpi::ArrayRef<int> PropertyContainer::EnumerateProperties(
+wpi::span<int> PropertyContainer::EnumerateProperties(
     wpi::SmallVectorImpl<int>& vec, CS_Status* status) const {
   if (!m_properties_cached && !CacheProperties(status)) {
     return {};
@@ -55,7 +54,7 @@ CS_PropertyKind PropertyContainer::GetPropertyKind(int property) const {
   return prop->propKind;
 }
 
-wpi::StringRef PropertyContainer::GetPropertyName(
+std::string_view PropertyContainer::GetPropertyName(
     int property, wpi::SmallVectorImpl<char>& buf, CS_Status* status) const {
   if (!m_properties_cached && !CacheProperties(status)) {
     return {};
@@ -108,7 +107,7 @@ void PropertyContainer::SetProperty(int property, int value,
     return;
   }
 
-  UpdatePropertyValue(property, false, value, wpi::Twine{});
+  UpdatePropertyValue(property, false, value, {});
 }
 
 int PropertyContainer::GetPropertyMin(int property, CS_Status* status) const {
@@ -164,7 +163,7 @@ int PropertyContainer::GetPropertyDefault(int property,
   return prop->defaultValue;
 }
 
-wpi::StringRef PropertyContainer::GetStringProperty(
+std::string_view PropertyContainer::GetStringProperty(
     int property, wpi::SmallVectorImpl<char>& buf, CS_Status* status) const {
   if (!m_properties_cached && !CacheProperties(status)) {
     return {};
@@ -181,10 +180,10 @@ wpi::StringRef PropertyContainer::GetStringProperty(
   }
   buf.clear();
   buf.append(prop->valueStr.begin(), prop->valueStr.end());
-  return wpi::StringRef(buf.data(), buf.size());
+  return {buf.data(), buf.size()};
 }
 
-void PropertyContainer::SetStringProperty(int property, const wpi::Twine& value,
+void PropertyContainer::SetStringProperty(int property, std::string_view value,
                                           CS_Status* status) {
   std::scoped_lock lock(m_mutex);
   auto prop = GetProperty(property);
@@ -225,7 +224,7 @@ std::vector<std::string> PropertyContainer::GetEnumPropertyChoices(
 }
 
 std::unique_ptr<PropertyImpl> PropertyContainer::CreateEmptyProperty(
-    const wpi::Twine& name) const {
+    std::string_view name) const {
   return std::make_unique<PropertyImpl>(name);
 }
 
@@ -237,16 +236,15 @@ bool PropertyContainer::CacheProperties(CS_Status* status) const {
 
 bool PropertyContainer::SetPropertiesJson(const wpi::json& config,
                                           wpi::Logger& logger,
-                                          wpi::StringRef logName,
+                                          std::string_view logName,
                                           CS_Status* status) {
   for (auto&& prop : config) {
     std::string name;
     try {
       name = prop.at("name").get<std::string>();
     } catch (const wpi::json::exception& e) {
-      WPI_WARNING(logger,
-                  logName << ": SetConfigJson: could not read property name: "
-                          << e.what());
+      WPI_WARNING(logger, "{}: SetConfigJson: could not read property name: {}",
+                  logName, e.what());
       continue;
     }
     int n = GetPropertyIndex(name);
@@ -254,24 +252,24 @@ bool PropertyContainer::SetPropertiesJson(const wpi::json& config,
       auto& v = prop.at("value");
       if (v.is_string()) {
         std::string val = v.get<std::string>();
-        WPI_INFO(logger, logName << ": SetConfigJson: setting property '"
-                                 << name << "' to '" << val << '\'');
+        WPI_INFO(logger, "{}: SetConfigJson: setting property '{}' to '{}'",
+                 logName, name, val);
         SetStringProperty(n, val, status);
       } else if (v.is_boolean()) {
         bool val = v.get<bool>();
-        WPI_INFO(logger, logName << ": SetConfigJson: setting property '"
-                                 << name << "' to " << val);
+        WPI_INFO(logger, "{}: SetConfigJson: setting property '{}' to {}",
+                 logName, name, val);
         SetProperty(n, val, status);
       } else {
         int val = v.get<int>();
-        WPI_INFO(logger, logName << ": SetConfigJson: setting property '"
-                                 << name << "' to " << val);
+        WPI_INFO(logger, "{}: SetConfigJson: setting property '{}' to {}",
+                 logName, name, val);
         SetProperty(n, val, status);
       }
     } catch (const wpi::json::exception& e) {
       WPI_WARNING(logger,
-                  logName << ": SetConfigJson: could not read property value: "
-                          << e.what());
+                  "{}: SetConfigJson: could not read property value: {}",
+                  logName, e.what());
       continue;
     }
   }

cscore/src/main/native/cpp/PropertyContainer.h

@@ -9,20 +9,20 @@
 #include <cstddef>
 #include <memory>
 #include <string>
+#include <string_view>
 #include <vector>
 
-#include <wpi/ArrayRef.h>
-#include <wpi/SmallVector.h>
 #include <wpi/StringMap.h>
-#include <wpi/StringRef.h>
-#include <wpi/Twine.h>
 #include <wpi/mutex.h>
+#include <wpi/span.h>
 
 #include "PropertyImpl.h"
 #include "cscore_cpp.h"
 
 namespace wpi {
 class Logger;
+template <typename T>
+class SmallVectorImpl;
 class json;
 }  // namespace wpi
 
@@ -32,28 +32,29 @@ class PropertyContainer {
  public:
   virtual ~PropertyContainer() = default;
 
-  int GetPropertyIndex(const wpi::Twine& name) const;
-  wpi::ArrayRef<int> EnumerateProperties(wpi::SmallVectorImpl<int>& vec,
-                                         CS_Status* status) const;
+  int GetPropertyIndex(std::string_view name) const;
+  wpi::span<int> EnumerateProperties(wpi::SmallVectorImpl<int>& vec,
+                                     CS_Status* status) const;
   CS_PropertyKind GetPropertyKind(int property) const;
-  wpi::StringRef GetPropertyName(int property, wpi::SmallVectorImpl<char>& buf,
-                                 CS_Status* status) const;
+  std::string_view GetPropertyName(int property,
+                                   wpi::SmallVectorImpl<char>& buf,
+                                   CS_Status* status) const;
   int GetProperty(int property, CS_Status* status) const;
   virtual void SetProperty(int property, int value, CS_Status* status);
   int GetPropertyMin(int property, CS_Status* status) const;
   int GetPropertyMax(int property, CS_Status* status) const;
   int GetPropertyStep(int property, CS_Status* status) const;
   int GetPropertyDefault(int property, CS_Status* status) const;
-  wpi::StringRef GetStringProperty(int property,
-                                   wpi::SmallVectorImpl<char>& buf,
-                                   CS_Status* status) const;
-  virtual void SetStringProperty(int property, const wpi::Twine& value,
+  std::string_view GetStringProperty(int property,
+                                     wpi::SmallVectorImpl<char>& buf,
+                                     CS_Status* status) const;
+  virtual void SetStringProperty(int property, std::string_view value,
                                  CS_Status* status);
   std::vector<std::string> GetEnumPropertyChoices(int property,
                                                   CS_Status* status) const;
 
   bool SetPropertiesJson(const wpi::json& config, wpi::Logger& logger,
-                         wpi::StringRef logName, CS_Status* status);
+                         std::string_view logName, CS_Status* status);
   wpi::json GetPropertiesJsonObject(CS_Status* status);
 
  protected:
@@ -76,10 +77,9 @@ class PropertyContainer {
   // @tparam NewFunc functor that returns a std::unique_ptr<PropertyImpl>
   // @tparam UpdateFunc functor that takes a PropertyImpl&.
   template <typename NewFunc, typename UpdateFunc>
-  int CreateOrUpdateProperty(const wpi::Twine& name, NewFunc newFunc,
+  int CreateOrUpdateProperty(std::string_view name, NewFunc newFunc,
                              UpdateFunc updateFunc) {
-    wpi::SmallVector<char, 64> nameBuf;
-    int& ndx = m_properties[name.toStringRef(nameBuf)];
+    int& ndx = m_properties[name];
     if (ndx == 0) {
       // create a new index
       ndx = m_propertyData.size() + 1;
@@ -91,7 +91,7 @@ class PropertyContainer {
     return ndx;
   }
   template <typename NewFunc>
-  int CreateProperty(const wpi::Twine& name, NewFunc newFunc) {
+  int CreateProperty(std::string_view name, NewFunc newFunc) {
     return CreateOrUpdateProperty(name, newFunc, [](PropertyImpl&) {});
   }
 
@@ -100,7 +100,7 @@ class PropertyContainer {
   // Note: called with m_mutex held.
   // The default implementation simply creates a PropertyImpl object.
   virtual std::unique_ptr<PropertyImpl> CreateEmptyProperty(
-      const wpi::Twine& name) const;
+      std::string_view name) const;
 
   // Cache properties.  Implementations must return false and set status to
   // CS_SOURCE_IS_DISCONNECTED if not possible to cache.
@@ -111,7 +111,7 @@ class PropertyContainer {
 
   // Update property value; must be called with m_mutex held.
   virtual void UpdatePropertyValue(int property, bool setString, int value,
-                                   const wpi::Twine& valueStr) = 0;
+                                   std::string_view valueStr) = 0;
 
   // Whether CacheProperties() has been successful at least once (and thus
   // should not be called again)