event_signal.h

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// Copyright (c) Space-ng, inc. All rights reserved.
#pragma once
 
#include <chrono>
#include <condition_variable>
#include <mutex>
 
namespace sol3::core {
 
class EventSignal {
 public:
  EventSignal() = default;
  ~EventSignal() = default;
 
  // No copy
  EventSignal(EventSignal const&) = delete;
  EventSignal& operator=(EventSignal const&) = delete;
 
  // No move
  EventSignal(EventSignal&&) = delete;
  EventSignal& operator=(EventSignal&&) = delete;
 
  bool wait(std::chrono::milliseconds timeout_ms) const {
    std::unique_lock<std::mutex> lock(mutex_);
    return cv_.wait_for(lock, timeout_ms, [this, seq = seq_] {
      // Use != instead of > to be robust to overflow (despite unlikeliness).
      return seq_ != seq;
    });
  }
 
  void notify() {
    std::lock_guard<std::mutex> lock(mutex_);
    ++seq_;
    cv_.notify_all();  // Wake all waiting threads
  }
 
 private:
  mutable std::mutex mutex_;
  mutable std::condition_variable cv_;
  // Used to track events. Each time notify() is called, we increment the
  // sequence number. Any subscriber waiting on an event reads the current
  // sequence number and checks if it increased while waiting.
  uint64_t seq_ = 0;
};
 
}  // namespace sol3::core