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// Copyright (c) 2012 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 BASE_ATOMIC_SEQUENCE_NUM_H_
#define BASE_ATOMIC_SEQUENCE_NUM_H_
#include <atomic>
#include "base/macros.h"
namespace base {
// AtomicSequenceNumber is a thread safe increasing sequence number generator.
// Its constructor doesn't emit a static initializer, so it's safe to use as a
// global variable or static member.
class AtomicSequenceNumber {
public:
constexpr AtomicSequenceNumber() = default;
// Returns an increasing sequence number starts from 0 for each call.
// This function can be called from any thread without data race.
inline int GetNext() { return seq_.fetch_add(1, std::memory_order_relaxed); }
private:
std::atomic_int seq_{0};
DISALLOW_COPY_AND_ASSIGN(AtomicSequenceNumber);
};
} // namespace base
#endif // BASE_ATOMIC_SEQUENCE_NUM_H_
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