// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_ATOMIC_SEQUENCE_NUM_H_
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#define BASE_ATOMIC_SEQUENCE_NUM_H_
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#include <atomic>
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#include "base/macros.h"
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namespace base {
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// AtomicSequenceNumber is a thread safe increasing sequence number generator.
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// Its constructor doesn't emit a static initializer, so it's safe to use as a
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// global variable or static member.
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class AtomicSequenceNumber {
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public:
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constexpr AtomicSequenceNumber() = default;
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// Returns an increasing sequence number starts from 0 for each call.
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// This function can be called from any thread without data race.
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inline int GetNext() { return seq_.fetch_add(1, std::memory_order_relaxed); }
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private:
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std::atomic_int seq_{0};
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DISALLOW_COPY_AND_ASSIGN(AtomicSequenceNumber);
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};
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} // namespace base
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#endif // BASE_ATOMIC_SEQUENCE_NUM_H_
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