react-native/ReactCommon/cxxreact/CxxMessageQueue.h

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// Copyright 2004-present Facebook. All Rights Reserved.
#pragma once
#include "MessageQueueThread.h"
#include <atomic>
#include <functional>
#include <chrono>
#include <mutex>
#include <thread>
#include <memory>
namespace facebook {
namespace react {
namespace detail {
template<bool clearOnWait>
class CVFlag {
public:
using time_point = std::chrono::steady_clock::time_point;
void set() {
std::lock_guard<std::mutex> lk(mtx_);
flag_ = true;
cv_.notify_one();
}
void wait() {
std::unique_lock<std::mutex> lk(mtx_);
cv_.wait(lk, [this] { return flag_; });
if (clearOnWait) flag_ = false;
}
bool wait_until(time_point d) {
std::unique_lock<std::mutex> lk(mtx_);
bool res = cv_.wait_until(lk, d, [this] { return flag_; });
if (clearOnWait && res) flag_ = false;
return res;
}
private:
bool flag_{false};
std::condition_variable cv_;
std::mutex mtx_;
};
using BinarySemaphore = CVFlag<true>;
using EventFlag = CVFlag<false>;
}
class CxxMessageQueue : public MessageQueueThread {
public:
CxxMessageQueue();
virtual ~CxxMessageQueue() override;
virtual void runOnQueue(std::function<void()>&&) override;
void runOnQueueDelayed(std::function<void()>&&, uint64_t delayMs);
// runOnQueueSync and quitSynchronous are dangerous. They should only be
// used for initialization and cleanup.
virtual void runOnQueueSync(std::function<void()>&&) override;
// Once quitSynchronous() returns, no further work should run on the queue.
virtual void quitSynchronous() override;
bool isOnQueue();
// This returns a function that will actually run the runloop.
// This runloop will return some time after quitSynchronous (or after this is destroyed).
//
// When running the runloop, it is important to ensure that no frames in the
// current stack have a strong reference to the queue.
//
// Only one thread should run the runloop.
static std::function<void()> getRunLoop(std::shared_ptr<CxxMessageQueue> mq);
static std::weak_ptr<CxxMessageQueue> current();
private:
class QueueRunner;
std::shared_ptr<QueueRunner> qr_;
};
}}