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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MOJO_EDK_SYSTEM_ATOMIC_FLAG_H_
#define MOJO_EDK_SYSTEM_ATOMIC_FLAG_H_
#include "base/atomicops.h"
#include "base/macros.h"
namespace mojo {
namespace edk {
// 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() : flag_(0) {}
~AtomicFlag() {}
void Set(bool value) {
base::subtle::Release_Store(&flag_, value ? 1 : 0);
}
bool Get() const {
return base::subtle::Acquire_Load(&flag_) ? true : false;
}
operator const bool() const { return Get(); }
private:
base::subtle::Atomic32 flag_;
DISALLOW_COPY_AND_ASSIGN(AtomicFlag);
};
} // namespace edk
} // namespace mojo
#endif // MOJO_EDK_SYSTEM_ATOMIC_FLAG_H_
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