src/dawn/platform/WorkerThread.h

// Copyright 2021 The Dawn & Tint Authors
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#ifndef SRC_DAWN_PLATFORM_WORKERTHREAD_H_
#define SRC_DAWN_PLATFORM_WORKERTHREAD_H_

#include <condition_variable>
#include <memory>
#include <mutex>
#include <queue>
#include <thread>
#include <vector>

#include "dawn/common/NonCopyable.h"
#include "dawn/platform/DawnPlatform.h"

namespace dawn::platform {

class AsyncWaitableEventImpl {
  public:
    AsyncWaitableEventImpl();

    void Wait();
    bool IsComplete();
    void MarkAsComplete();

  private:
    std::mutex mMutex;
    std::condition_variable mCondition;
    bool mIsComplete;
};

struct AsyncWorkerThreadPoolTask {
    dawn::platform::PostWorkerTaskCallback callback;
    void* userdata;
    std::shared_ptr<AsyncWaitableEventImpl> waitableEventImpl;
};

class AsyncWorkerThreadPool : public dawn::platform::WorkerTaskPool, public NonCopyable {
  public:
    static constexpr uint32_t kDefaultThreadCount = 2;

    explicit AsyncWorkerThreadPool(uint32_t maxThreadCount = kDefaultThreadCount);
    ~AsyncWorkerThreadPool() override;

    std::unique_ptr<dawn::platform::WaitableEvent> PostWorkerTask(
        dawn::platform::PostWorkerTaskCallback callback,
        void* userdata) override;

  private:
    void EnsureThreads();
    void ThreadLoop();

    const uint32_t mMaxThreads;
    std::vector<std::thread> mThreads;
    std::queue<AsyncWorkerThreadPoolTask> mPendingTasks;
    std::mutex mMutex;
    std::condition_variable mCondition;
    bool mIsDestroyed = false;
};

}  // namespace dawn::platform

#endif  // SRC_DAWN_PLATFORM_WORKERTHREAD_H_