src/dawn/common/Mutex.h

// Copyright 2023 The Dawn & Tint Authors
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#ifndef SRC_DAWN_COMMON_MUTEX_H_
#define SRC_DAWN_COMMON_MUTEX_H_

#include <atomic>
#include <mutex>
#include <thread>
#include <utility>

#include "dawn/common/Assert.h"
#include "dawn/common/NonCopyable.h"
#include "dawn/common/NonMovable.h"
#include "dawn/common/Ref.h"
#include "dawn/common/RefCounted.h"

namespace dawn {
class Mutex : public RefCounted, NonCopyable {
  public:
    template <typename MutexRef>
    struct AutoLockBase : NonMovable {
        AutoLockBase() : mMutex(nullptr) {}
        explicit AutoLockBase(MutexRef mutex) : mMutex(std::move(mutex)) {
            if (mMutex != nullptr) {
                mMutex->Lock();
            }
        }
        ~AutoLockBase() {
            if (mMutex != nullptr) {
                mMutex->Unlock();
            }
        }

      private:
        MutexRef mMutex;
    };

    // This scoped lock won't keep the mutex alive.
    using AutoLock = AutoLockBase<Mutex*>;
    // This scoped lock will keep the mutex alive until out of scope.
    using AutoLockAndHoldRef = AutoLockBase<Ref<Mutex>>;

    ~Mutex() override;

    void Lock();
    void Unlock();

    // This method is only enabled when DAWN_ENABLE_ASSERTS is turned on.
    // Thus it should only be wrapped inside DAWN_ASSERT() macro.
    // i.e. DAWN_ASSERT(mutex.IsLockedByCurrentThread())
    bool IsLockedByCurrentThread();

  private:
#if defined(DAWN_ENABLE_ASSERTS)
    std::atomic<std::thread::id> mOwner;
#endif  // DAWN_ENABLE_ASSERTS
    std::mutex mNativeMutex;
};

}  // namespace dawn

#endif