[wpiutil] Add mDNS resolver and announcer (#3733)

wpiutil/src/main/native/include/wpi/MulticastServiceAnnouncer.h

@@ -0,0 +1,61 @@
+// 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 <stdint.h>
+
+#ifdef __cplusplus
+#include <memory>
+#include <string>
+#include <string_view>
+#include <utility>
+
+#include "wpi/span.h"
+namespace wpi {
+class MulticastServiceAnnouncer {
+ public:
+  MulticastServiceAnnouncer(
+      std::string_view serviceName, std::string_view serviceType, int port,
+      wpi::span<const std::pair<std::string, std::string>> txt);
+  MulticastServiceAnnouncer(
+      std::string_view serviceName, std::string_view serviceType, int port,
+      wpi::span<const std::pair<std::string_view, std::string_view>> txt);
+  ~MulticastServiceAnnouncer() noexcept;
+  void Start();
+  void Stop();
+  bool HasImplementation() const;
+  struct Impl;
+
+ private:
+  std::unique_ptr<Impl> pImpl;
+};
+}  // namespace wpi
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef unsigned int WPI_MulticastServiceAnnouncerHandle;  // NOLINT
+
+WPI_MulticastServiceAnnouncerHandle WPI_CreateMulticastServiceAnnouncer(
+    const char* serviceName, const char* serviceType, int32_t port,
+    int32_t txtCount, const char** keys, const char** values);
+
+void WPI_FreeMulticastServiceAnnouncer(
+    WPI_MulticastServiceAnnouncerHandle handle);
+
+void WPI_StartMulticastServiceAnnouncer(
+    WPI_MulticastServiceAnnouncerHandle handle);
+
+void WPI_StopMulticastServiceAnnouncer(
+    WPI_MulticastServiceAnnouncerHandle handle);
+
+int32_t WPI_GetMulticastServiceAnnouncerHasImplementation(
+    WPI_MulticastServiceAnnouncerHandle handle);
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif

wpiutil/src/main/native/include/wpi/MulticastServiceResolver.h

@@ -0,0 +1,87 @@
+// 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 "wpi/Synchronization.h"
+
+#ifdef __cplusplus
+#include <functional>
+#include <memory>
+#include <string>
+#include <string_view>
+#include <utility>
+#include <vector>
+
+#include "wpi/ConcurrentQueue.h"
+#include "wpi/span.h"
+namespace wpi {
+class MulticastServiceResolver {
+ public:
+  explicit MulticastServiceResolver(std::string_view serviceType);
+  ~MulticastServiceResolver() noexcept;
+  struct ServiceData {
+    unsigned int ipv4Address;
+    int port;
+    std::string serviceName;
+    std::string hostName;
+    std::vector<std::pair<std::string, std::string>> txt;
+  };
+  void Start();
+  void Stop();
+  WPI_EventHandle GetEventHandle() { return event.GetHandle(); }
+  ServiceData GetData() { return eventQueue.pop(); }
+  bool HasImplementation() const;
+  struct Impl;
+
+ private:
+  wpi::Event event;
+  wpi::ConcurrentQueue<ServiceData> eventQueue;
+  std::unique_ptr<Impl> pImpl;
+};
+}  // namespace wpi
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef unsigned int WPI_MulticastServiceResolverHandle;  // NOLINT
+
+WPI_MulticastServiceResolverHandle WPI_CreateMulticastServiceResolver(
+    const char* serviceType);
+
+void WPI_FreeMulticastServiceResolver(
+    WPI_MulticastServiceResolverHandle handle);
+
+void WPI_StartMulticastServiceResolver(
+    WPI_MulticastServiceResolverHandle handle);
+
+void WPI_StopMulticastServiceResolver(
+    WPI_MulticastServiceResolverHandle handle);
+
+int32_t WPI_GetMulticastServiceResolverHasImplementation(
+    WPI_MulticastServiceResolverHandle handle);
+
+WPI_EventHandle WPI_GetMulticastServiceResolverEventHandle(
+    WPI_MulticastServiceResolverHandle handle);
+
+typedef struct WPI_ServiceData {  // NOLINT
+  uint32_t ipv4Address;
+  int32_t port;
+  const char* serviceName;
+  const char* hostName;
+  int32_t txtCount;
+  const char** txtKeys;
+  const char** txtValues;
+} WPI_ServiceData;
+
+WPI_ServiceData* WPI_GetMulticastServiceResolverData(
+    WPI_MulticastServiceResolverHandle handle);
+
+void WPI_FreeServiceData(WPI_ServiceData* serviceData);
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif

wpiutil/src/main/native/include/wpi/jni_util.h

@@ -566,6 +566,28 @@ inline jobjectArray MakeJStringArray(JNIEnv* env, span<const std::string> arr) {
   return jarr;
 }
 
+/**
+ * Convert an array of std::string into a jarray of jstring.
+ *
+ * @param env JRE environment.
+ * @param arr Array to convert.
+ */
+inline jobjectArray MakeJStringArray(JNIEnv* env, span<std::string_view> arr) {
+  static JClass stringCls{env, "java/lang/String"};
+  if (!stringCls) {
+    return nullptr;
+  }
+  jobjectArray jarr = env->NewObjectArray(arr.size(), stringCls, nullptr);
+  if (!jarr) {
+    return nullptr;
+  }
+  for (size_t i = 0; i < arr.size(); ++i) {
+    JLocal<jstring> elem{env, MakeJString(env, arr[i])};
+    env->SetObjectArrayElement(jarr, i, elem.obj());
+  }
+  return jarr;
+}
+
 /**
  * Generic callback thread implementation.
  *