// 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 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; AtomicSequenceNumber(const AtomicSequenceNumber&) = delete; AtomicSequenceNumber& operator=(const AtomicSequenceNumber&) = delete; // 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}; }; } // namespace base #endif // BASE_ATOMIC_SEQUENCE_NUM_H_