Futex.h - mozsearch

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/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_Futex_h

#define mozilla_Futex_h

#include <atomic>

#include <cstdint>

#include "mozilla/TimeStamp.h"

namespace mozilla {

template <typename T>

struct FutexImpl {

  using ValueType = T;

  std::atomic<T> mValue{0};

  // Waits until the value changes from aExpected, the futex is woken, or

  // (when aTimeout is non-null) the timeout elapses. Returns false on timeout,

  // true otherwise (including spurious wake-ups!).

  [[nodiscard]] bool wait(T aExpected, const TimeDuration* aTimeout = nullptr);

  void wake();

  void wakeAll();

};

using Futex = FutexImpl<uint32_t>;

#ifdef XP_WIN

using SmallFutex = FutexImpl<uint8_t>;

#else

// On Linux the futex word must be a 32-bit value.

using SmallFutex = Futex;

#endif

}  // namespace mozilla

#endif