61 lines
1.7 KiB
C
61 lines
1.7 KiB
C
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// 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 "base/atomicops.h"
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#include "base/basictypes.h"
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namespace base {
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class AtomicSequenceNumber;
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// Static (POD) AtomicSequenceNumber that MUST be used in global scope (or
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// non-function scope) ONLY. This implementation does not generate any static
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// initializer. Note that it does not implement any constructor which means
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// that its fields are not initialized except when it is stored in the global
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// data section (.data in ELF). If you want to allocate an atomic sequence
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// number on the stack (or heap), please use the AtomicSequenceNumber class
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// declared below.
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class StaticAtomicSequenceNumber {
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public:
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inline int GetNext() {
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return static_cast<int>(
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base::subtle::NoBarrier_AtomicIncrement(&seq_, 1) - 1);
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}
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private:
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friend class AtomicSequenceNumber;
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inline void Reset() {
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base::subtle::Release_Store(&seq_, 0);
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}
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base::subtle::Atomic32 seq_;
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};
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// AtomicSequenceNumber that can be stored and used safely (i.e. its fields are
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// always initialized as opposed to StaticAtomicSequenceNumber declared above).
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// Please use StaticAtomicSequenceNumber if you want to declare an atomic
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// sequence number in the global scope.
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class AtomicSequenceNumber {
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public:
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AtomicSequenceNumber() {
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seq_.Reset();
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}
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inline int GetNext() {
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return seq_.GetNext();
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}
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private:
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StaticAtomicSequenceNumber seq_;
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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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