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comparison: security/sandbox/chromium/base/atomic_sequence_num.h
security/sandbox/chromium/base/atomic_sequence_num.h
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| 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. | |
| 4 | |
| 5 #ifndef BASE_ATOMIC_SEQUENCE_NUM_H_ | |
| 6 #define BASE_ATOMIC_SEQUENCE_NUM_H_ | |
| 7 | |
| 8 #include "base/atomicops.h" | |
| 9 #include "base/basictypes.h" | |
| 10 | |
| 11 namespace base { | |
| 12 | |
| 13 class AtomicSequenceNumber; | |
| 14 | |
| 15 // Static (POD) AtomicSequenceNumber that MUST be used in global scope (or | |
| 16 // non-function scope) ONLY. This implementation does not generate any static | |
| 17 // initializer. Note that it does not implement any constructor which means | |
| 18 // that its fields are not initialized except when it is stored in the global | |
| 19 // data section (.data in ELF). If you want to allocate an atomic sequence | |
| 20 // number on the stack (or heap), please use the AtomicSequenceNumber class | |
| 21 // declared below. | |
| 22 class StaticAtomicSequenceNumber { | |
| 23 public: | |
| 24 inline int GetNext() { | |
| 25 return static_cast<int>( | |
| 26 base::subtle::NoBarrier_AtomicIncrement(&seq_, 1) - 1); | |
| 27 } | |
| 28 | |
| 29 private: | |
| 30 friend class AtomicSequenceNumber; | |
| 31 | |
| 32 inline void Reset() { | |
| 33 base::subtle::Release_Store(&seq_, 0); | |
| 34 } | |
| 35 | |
| 36 base::subtle::Atomic32 seq_; | |
| 37 }; | |
| 38 | |
| 39 // AtomicSequenceNumber that can be stored and used safely (i.e. its fields are | |
| 40 // always initialized as opposed to StaticAtomicSequenceNumber declared above). | |
| 41 // Please use StaticAtomicSequenceNumber if you want to declare an atomic | |
| 42 // sequence number in the global scope. | |
| 43 class AtomicSequenceNumber { | |
| 44 public: | |
| 45 AtomicSequenceNumber() { | |
| 46 seq_.Reset(); | |
| 47 } | |
| 48 | |
| 49 inline int GetNext() { | |
| 50 return seq_.GetNext(); | |
| 51 } | |
| 52 | |
| 53 private: | |
| 54 StaticAtomicSequenceNumber seq_; | |
| 55 DISALLOW_COPY_AND_ASSIGN(AtomicSequenceNumber); | |
| 56 }; | |
| 57 | |
| 58 } // namespace base | |
| 59 | |
| 60 #endif // BASE_ATOMIC_SEQUENCE_NUM_H_ |
