| // Copyright 2012 The Chromium Authors |
| // 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> |
| |
| 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_ |