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// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MOJO_CORE_ATOMIC_FLAG_H_
#define MOJO_CORE_ATOMIC_FLAG_H_
#include <atomic>
namespace mojo {
namespace core {
// AtomicFlag is a boolean flag that can be set and tested atomically. It is
// intended to be used to fast-path checks where the common case would normally
// release the governing mutex immediately after checking.
//
// Example usage:
// void DoFoo(Bar* bar) {
// AutoLock l(lock_);
// queue_.push_back(bar);
// flag_.Set(true);
// }
//
// void Baz() {
// if (!flag_) // Assume this is the common case.
// return;
//
// AutoLock l(lock_);
// ... drain queue_ ...
// flag_.Set(false);
// }
class AtomicFlag {
public:
AtomicFlag();
AtomicFlag(const AtomicFlag&) = delete;
AtomicFlag& operator=(const AtomicFlag&) = delete;
~AtomicFlag() = default;
void Set(bool value) { flag_.store(value, std::memory_order_release); }
bool Get() const { return flag_.load(std::memory_order_acquire); }
operator const bool() const { return Get(); }
private:
std::atomic<bool> flag_;
};
} // namespace core
} // namespace mojo
#endif // MOJO_CORE_ATOMIC_FLAG_H_
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