MulticastServiceResolver.h

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// 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/util/Synchronization.hpp"
 
#ifdef __cplusplus
 
#include <functional>
#include <memory>
#include <string>
#include <string_view>
#include <utility>
#include <vector>
 
#include "wpi/util/mutex.hpp"
 
namespace wpi::net {
 
class MulticastServiceResolver {
 public:
  explicit MulticastServiceResolver(std::string_view serviceType);
 
  ~MulticastServiceResolver() noexcept;
 
  struct ServiceData {
    /// IPv4 address in host order.
    unsigned int ipv4Address;
    /// Port number in host order.
    int port;
    /// Service name.
    std::string serviceName;
    /// Host name.
    std::string hostName;
    /// Service data payload.
    std::vector<std::pair<std::string, std::string>> txt;
  };
 
  /**
   * Set a copy callback to be called when a service is resolved.
   * Takes presidence over the move callback. Return true to
   * not send the data to the event queue.
   */
  bool SetCopyCallback(std::function<bool(const ServiceData&)> callback);
 
  /**
   * Set a move callback to be called when a service is resolved.
   * Data is moved into the function and cannot be added to the event queue.
   */
  bool SetMoveCallback(std::function<void(ServiceData&&)> callback);
 
  /**
   * Starts multicast service resolver.
   */
  void Start();
 
  /**
   * Stops multicast service resolver.
   */
  void Stop();
 
  /**
   * Returns event handle.
   *
   * @return Event handle.
   */
  WPI_EventHandle GetEventHandle() const { return event.GetHandle(); }
 
  /**
   * Returns multicast service resolver data.
   *
   * @return Multicast service resolver data.
   */
  std::vector<ServiceData> GetData() {
    std::scoped_lock lock{mutex};
 
    event.Reset();
    if (queue.empty()) {
      return {};
    }
 
    std::vector<ServiceData> ret;
    queue.swap(ret);
    return ret;
  }
 
  /**
   * Returns true if there's a multicast service resolver implementation.
   *
   * @return True if there's a multicast service resolver implementation.
   */
  bool HasImplementation() const;
 
  struct Impl;
 
 private:
  void PushData(ServiceData&& data) {
    std::scoped_lock lock{mutex};
 
    if (copyCallback) {
      if (!copyCallback(data)) {
        queue.emplace_back(std::forward<ServiceData>(data));
        event.Set();
      }
    } else if (moveCallback) {
      moveCallback(std::move(data));
    } else {
      queue.emplace_back(std::forward<ServiceData>(data));
      event.Set();
    }
  }
 
  wpi::util::Event event{true};
  std::vector<ServiceData> queue;
  wpi::util::mutex mutex;
  std::function<bool(const ServiceData&)> copyCallback;
  std::function<void(ServiceData&&)> moveCallback;
  std::unique_ptr<Impl> pImpl;
};
 
}  // namespace wpi::net
 
#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, int32_t* dataCount);
 
void WPI_FreeServiceData(WPI_ServiceData* serviceData, int32_t length);
 
#ifdef __cplusplus
}  // extern "C"
#endif