[wpiutil, wpilib] Add FileLogger and log console output (#6977)

wpiutil/src/main/native/cpp/FileLogger.cpp

@@ -0,0 +1,105 @@
+// 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 "wpi/FileLogger.h"
+
+#ifdef __linux__
+#include <fcntl.h>
+#include <sys/inotify.h>
+#include <unistd.h>
+#endif
+
+#include <string>
+#include <string_view>
+#include <tuple>
+#include <utility>
+
+#include "wpi/StringExtras.h"
+
+namespace wpi {
+FileLogger::FileLogger(std::string_view file,
+                       std::function<void(std::string_view)> callback)
+#ifdef __linux__
+    : m_fileHandle{open(file.data(), O_RDONLY)},
+      m_inotifyHandle{inotify_init()},
+      m_inotifyWatchHandle{
+          inotify_add_watch(m_inotifyHandle, file.data(), IN_MODIFY)},
+      m_thread{[=, this] {
+        char buf[4000];
+        struct inotify_event ev;
+        int len = 0;
+        lseek(m_fileHandle, 0, SEEK_END);
+        while ((len = read(m_inotifyHandle, &ev, sizeof(ev))) > 0) {
+          int bufLen = 0;
+          if ((bufLen = read(m_fileHandle, buf, sizeof(buf)) > 0)) {
+            callback(std::string_view{buf, static_cast<size_t>(bufLen)});
+          }
+        }
+      }}
+#endif
+{
+}
+FileLogger::FileLogger(std::string_view file, log::DataLog& log,
+                       std::string_view key)
+    : FileLogger(file, LineBuffer([entry = log.Start(key, "string"),
+                                   &log](std::string_view line) {
+                   log.AppendString(entry, line, 0);
+                 })) {}
+FileLogger::FileLogger(FileLogger&& other)
+#ifdef __linux__
+    : m_fileHandle{std::exchange(other.m_fileHandle, -1)},
+      m_inotifyHandle{std::exchange(other.m_inotifyHandle, -1)},
+      m_inotifyWatchHandle{std::exchange(other.m_inotifyWatchHandle, -1)},
+      m_thread{std::move(other.m_thread)}
+#endif
+{
+}
+FileLogger& FileLogger::operator=(FileLogger&& rhs) {
+#ifdef __linux__
+  std::swap(m_fileHandle, rhs.m_fileHandle);
+  std::swap(m_inotifyHandle, rhs.m_inotifyHandle);
+  std::swap(m_inotifyWatchHandle, rhs.m_inotifyWatchHandle);
+  m_thread = std::move(rhs.m_thread);
+#endif
+  return *this;
+}
+FileLogger::~FileLogger() {
+#ifdef __linux__
+  if (m_inotifyWatchHandle != -1) {
+    inotify_rm_watch(m_inotifyHandle, m_inotifyWatchHandle);
+  }
+  if (m_inotifyHandle != -1) {
+    close(m_inotifyHandle);
+  }
+  if (m_fileHandle != -1) {
+    close(m_fileHandle);
+  }
+  if (m_thread.joinable()) {
+    m_thread.join();
+  }
+#endif
+}
+std::function<void(std::string_view)> FileLogger::LineBuffer(
+    std::function<void(std::string_view)> callback) {
+  return [callback,
+          buf = wpi::SmallVector<char, 32>{}](std::string_view data) mutable {
+    if (!wpi::contains(data, "\n")) {
+      buf.append(data.begin(), data.end());
+      return;
+    }
+    std::string_view line;
+    std::string_view remainingData;
+    std::tie(line, remainingData) = wpi::split(data, "\n");
+    buf.append(line.begin(), line.end());
+    callback(std::string_view{buf.data(), buf.size()});
+
+    while (wpi::contains(remainingData, "\n")) {
+      std::tie(line, remainingData) = wpi::split(remainingData, "\n");
+      callback(line);
+    }
+    buf.clear();
+    buf.append(remainingData.begin(), remainingData.end());
+  };
+}
+}  // namespace wpi