security/sandbox/chromium/base/atomic_ref_count.h@6474c204b198 (annotated)
security/sandbox/chromium/base/atomic_ref_count.h
Wed, 31 Dec 2014 06:09:35 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Wed, 31 Dec 2014 06:09:35 +0100
- changeset 0
- 6474c204b198
- permissions
- -rw-r--r--
Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.
| michael@0 | 1 | // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
| michael@0 | 2 | // Use of this source code is governed by a BSD-style license that can be |
| michael@0 | 3 | // found in the LICENSE file. |
| michael@0 | 4 | |
| michael@0 | 5 | // This is a low level implementation of atomic semantics for reference |
| michael@0 | 6 | // counting. Please use base/memory/ref_counted.h directly instead. |
| michael@0 | 7 | // |
| michael@0 | 8 | // The implementation includes annotations to avoid some false positives |
| michael@0 | 9 | // when using data race detection tools. |
| michael@0 | 10 | |
| michael@0 | 11 | #ifndef BASE_ATOMIC_REF_COUNT_H_ |
| michael@0 | 12 | #define BASE_ATOMIC_REF_COUNT_H_ |
| michael@0 | 13 | |
| michael@0 | 14 | #include "base/atomicops.h" |
| michael@0 | 15 | #include "base/third_party/dynamic_annotations/dynamic_annotations.h" |
| michael@0 | 16 | |
| michael@0 | 17 | namespace base { |
| michael@0 | 18 | |
| michael@0 | 19 | typedef subtle::Atomic32 AtomicRefCount; |
| michael@0 | 20 | |
| michael@0 | 21 | // Increment a reference count by "increment", which must exceed 0. |
| michael@0 | 22 | inline void AtomicRefCountIncN(volatile AtomicRefCount *ptr, |
| michael@0 | 23 | AtomicRefCount increment) { |
| michael@0 | 24 | subtle::NoBarrier_AtomicIncrement(ptr, increment); |
| michael@0 | 25 | } |
| michael@0 | 26 | |
| michael@0 | 27 | // Decrement a reference count by "decrement", which must exceed 0, |
| michael@0 | 28 | // and return whether the result is non-zero. |
| michael@0 | 29 | // Insert barriers to ensure that state written before the reference count |
| michael@0 | 30 | // became zero will be visible to a thread that has just made the count zero. |
| michael@0 | 31 | inline bool AtomicRefCountDecN(volatile AtomicRefCount *ptr, |
| michael@0 | 32 | AtomicRefCount decrement) { |
| michael@0 | 33 | ANNOTATE_HAPPENS_BEFORE(ptr); |
| michael@0 | 34 | bool res = (subtle::Barrier_AtomicIncrement(ptr, -decrement) != 0); |
| michael@0 | 35 | if (!res) { |
| michael@0 | 36 | ANNOTATE_HAPPENS_AFTER(ptr); |
| michael@0 | 37 | } |
| michael@0 | 38 | return res; |
| michael@0 | 39 | } |
| michael@0 | 40 | |
| michael@0 | 41 | // Increment a reference count by 1. |
| michael@0 | 42 | inline void AtomicRefCountInc(volatile AtomicRefCount *ptr) { |
| michael@0 | 43 | base::AtomicRefCountIncN(ptr, 1); |
| michael@0 | 44 | } |
| michael@0 | 45 | |
| michael@0 | 46 | // Decrement a reference count by 1 and return whether the result is non-zero. |
| michael@0 | 47 | // Insert barriers to ensure that state written before the reference count |
| michael@0 | 48 | // became zero will be visible to a thread that has just made the count zero. |
| michael@0 | 49 | inline bool AtomicRefCountDec(volatile AtomicRefCount *ptr) { |
| michael@0 | 50 | return base::AtomicRefCountDecN(ptr, 1); |
| michael@0 | 51 | } |
| michael@0 | 52 | |
| michael@0 | 53 | // Return whether the reference count is one. If the reference count is used |
| michael@0 | 54 | // in the conventional way, a refrerence count of 1 implies that the current |
| michael@0 | 55 | // thread owns the reference and no other thread shares it. This call performs |
| michael@0 | 56 | // the test for a reference count of one, and performs the memory barrier |
| michael@0 | 57 | // needed for the owning thread to act on the object, knowing that it has |
| michael@0 | 58 | // exclusive access to the object. |
| michael@0 | 59 | inline bool AtomicRefCountIsOne(volatile AtomicRefCount *ptr) { |
| michael@0 | 60 | bool res = (subtle::Acquire_Load(ptr) == 1); |
| michael@0 | 61 | if (res) { |
| michael@0 | 62 | ANNOTATE_HAPPENS_AFTER(ptr); |
| michael@0 | 63 | } |
| michael@0 | 64 | return res; |
| michael@0 | 65 | } |
| michael@0 | 66 | |
| michael@0 | 67 | // Return whether the reference count is zero. With conventional object |
| michael@0 | 68 | // referencing counting, the object will be destroyed, so the reference count |
| michael@0 | 69 | // should never be zero. Hence this is generally used for a debug check. |
| michael@0 | 70 | inline bool AtomicRefCountIsZero(volatile AtomicRefCount *ptr) { |
| michael@0 | 71 | bool res = (subtle::Acquire_Load(ptr) == 0); |
| michael@0 | 72 | if (res) { |
| michael@0 | 73 | ANNOTATE_HAPPENS_AFTER(ptr); |
| michael@0 | 74 | } |
| michael@0 | 75 | return res; |
| michael@0 | 76 | } |
| michael@0 | 77 | |
| michael@0 | 78 | } // namespace base |
| michael@0 | 79 | |
| michael@0 | 80 | #endif // BASE_ATOMIC_REF_COUNT_H_ |
