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comparison: ipc/chromium/src/base/atomic_ref_count.h
ipc/chromium/src/base/atomic_ref_count.h
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| 1 // Copyright (c) 2006-2008 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 // This is a low level implementation of atomic semantics for reference | |
| 6 // counting. Please use base/ref_counted.h directly instead. | |
| 7 | |
| 8 #ifndef BASE_ATOMIC_REF_COUNT_H_ | |
| 9 #define BASE_ATOMIC_REF_COUNT_H_ | |
| 10 | |
| 11 #include "base/atomicops.h" | |
| 12 | |
| 13 namespace base { | |
| 14 | |
| 15 typedef subtle::Atomic32 AtomicRefCount; | |
| 16 | |
| 17 // Increment a reference count by "increment", which must exceed 0. | |
| 18 inline void AtomicRefCountIncN(volatile AtomicRefCount *ptr, | |
| 19 AtomicRefCount increment) { | |
| 20 subtle::NoBarrier_AtomicIncrement(ptr, increment); | |
| 21 } | |
| 22 | |
| 23 // Decrement a reference count by "decrement", which must exceed 0, | |
| 24 // and return whether the result is non-zero. | |
| 25 // Insert barriers to ensure that state written before the reference count | |
| 26 // became zero will be visible to a thread that has just made the count zero. | |
| 27 inline bool AtomicRefCountDecN(volatile AtomicRefCount *ptr, | |
| 28 AtomicRefCount decrement) { | |
| 29 return subtle::Barrier_AtomicIncrement(ptr, -decrement) != 0; | |
| 30 } | |
| 31 | |
| 32 // Increment a reference count by 1. | |
| 33 inline void AtomicRefCountInc(volatile AtomicRefCount *ptr) { | |
| 34 base::AtomicRefCountIncN(ptr, 1); | |
| 35 } | |
| 36 | |
| 37 // Decrement a reference count by 1 and return whether the result is non-zero. | |
| 38 // Insert barriers to ensure that state written before the reference count | |
| 39 // became zero will be visible to a thread that has just made the count zero. | |
| 40 inline bool AtomicRefCountDec(volatile AtomicRefCount *ptr) { | |
| 41 return base::AtomicRefCountDecN(ptr, 1); | |
| 42 } | |
| 43 | |
| 44 // Return whether the reference count is one. If the reference count is used | |
| 45 // in the conventional way, a refrerence count of 1 implies that the current | |
| 46 // thread owns the reference and no other thread shares it. This call performs | |
| 47 // the test for a reference count of one, and performs the memory barrier | |
| 48 // needed for the owning thread to act on the object, knowing that it has | |
| 49 // exclusive access to the object. | |
| 50 inline bool AtomicRefCountIsOne(volatile AtomicRefCount *ptr) { | |
| 51 return subtle::Acquire_Load(ptr) == 1; | |
| 52 } | |
| 53 | |
| 54 // Return whether the reference count is zero. With conventional object | |
| 55 // referencing counting, the object will be destroyed, so the reference count | |
| 56 // should never be zero. Hence this is generally used for a debug check. | |
| 57 inline bool AtomicRefCountIsZero(volatile AtomicRefCount *ptr) { | |
| 58 return subtle::Acquire_Load(ptr) == 0; | |
| 59 } | |
| 60 | |
| 61 } // namespace base | |
| 62 | |
| 63 #endif // BASE_ATOMIC_REF_COUNT_H_ |
