1 files changed, 33 insertions, 0 deletions
diff --git a/security/sandbox/chromium/base/atomic_sequence_num.h b/security/sandbox/chromium/base/atomic_sequence_num.h
new file mode 100644
index 0000000000..717e37a60b
--- /dev/null
+++ b/security/sandbox/chromium/base/atomic_sequence_num.h
@@ -0,0 +1,33 @@
+// 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_