1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #ifndef BASE_ATOMIC_SEQUENCE_NUM_H_
6 #define BASE_ATOMIC_SEQUENCE_NUM_H_
12 // AtomicSequenceNumber is a thread safe increasing sequence number generator.
13 // Its constructor doesn't emit a static initializer, so it's safe to use as a
14 // global variable or static member.
15 class AtomicSequenceNumber {
17 constexpr AtomicSequenceNumber() = default;
18 AtomicSequenceNumber(const AtomicSequenceNumber&) = delete;
19 AtomicSequenceNumber& operator=(const AtomicSequenceNumber&) = delete;
21 // Returns an increasing sequence number starts from 0 for each call.
22 // This function can be called from any thread without data race.
23 inline int GetNext() { return seq_.fetch_add(1, std::memory_order_relaxed); }
26 std::atomic_int seq_{0};
31 #endif // BASE_ATOMIC_SEQUENCE_NUM_H_