1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/security/sandbox/chromium/base/atomic_ref_count.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,80 @@
1.4 +// Copyright (c) 2011 The Chromium Authors. All rights reserved.
1.5 +// Use of this source code is governed by a BSD-style license that can be
1.6 +// found in the LICENSE file.
1.7 +
1.8 +// This is a low level implementation of atomic semantics for reference
1.9 +// counting. Please use base/memory/ref_counted.h directly instead.
1.10 +//
1.11 +// The implementation includes annotations to avoid some false positives
1.12 +// when using data race detection tools.
1.13 +
1.14 +#ifndef BASE_ATOMIC_REF_COUNT_H_
1.15 +#define BASE_ATOMIC_REF_COUNT_H_
1.16 +
1.17 +#include "base/atomicops.h"
1.18 +#include "base/third_party/dynamic_annotations/dynamic_annotations.h"
1.19 +
1.20 +namespace base {
1.21 +
1.22 +typedef subtle::Atomic32 AtomicRefCount;
1.23 +
1.24 +// Increment a reference count by "increment", which must exceed 0.
1.25 +inline void AtomicRefCountIncN(volatile AtomicRefCount *ptr,
1.26 + AtomicRefCount increment) {
1.27 + subtle::NoBarrier_AtomicIncrement(ptr, increment);
1.28 +}
1.29 +
1.30 +// Decrement a reference count by "decrement", which must exceed 0,
1.31 +// and return whether the result is non-zero.
1.32 +// Insert barriers to ensure that state written before the reference count
1.33 +// became zero will be visible to a thread that has just made the count zero.
1.34 +inline bool AtomicRefCountDecN(volatile AtomicRefCount *ptr,
1.35 + AtomicRefCount decrement) {
1.36 + ANNOTATE_HAPPENS_BEFORE(ptr);
1.37 + bool res = (subtle::Barrier_AtomicIncrement(ptr, -decrement) != 0);
1.38 + if (!res) {
1.39 + ANNOTATE_HAPPENS_AFTER(ptr);
1.40 + }
1.41 + return res;
1.42 +}
1.43 +
1.44 +// Increment a reference count by 1.
1.45 +inline void AtomicRefCountInc(volatile AtomicRefCount *ptr) {
1.46 + base::AtomicRefCountIncN(ptr, 1);
1.47 +}
1.48 +
1.49 +// Decrement a reference count by 1 and return whether the result is non-zero.
1.50 +// Insert barriers to ensure that state written before the reference count
1.51 +// became zero will be visible to a thread that has just made the count zero.
1.52 +inline bool AtomicRefCountDec(volatile AtomicRefCount *ptr) {
1.53 + return base::AtomicRefCountDecN(ptr, 1);
1.54 +}
1.55 +
1.56 +// Return whether the reference count is one. If the reference count is used
1.57 +// in the conventional way, a refrerence count of 1 implies that the current
1.58 +// thread owns the reference and no other thread shares it. This call performs
1.59 +// the test for a reference count of one, and performs the memory barrier
1.60 +// needed for the owning thread to act on the object, knowing that it has
1.61 +// exclusive access to the object.
1.62 +inline bool AtomicRefCountIsOne(volatile AtomicRefCount *ptr) {
1.63 + bool res = (subtle::Acquire_Load(ptr) == 1);
1.64 + if (res) {
1.65 + ANNOTATE_HAPPENS_AFTER(ptr);
1.66 + }
1.67 + return res;
1.68 +}
1.69 +
1.70 +// Return whether the reference count is zero. With conventional object
1.71 +// referencing counting, the object will be destroyed, so the reference count
1.72 +// should never be zero. Hence this is generally used for a debug check.
1.73 +inline bool AtomicRefCountIsZero(volatile AtomicRefCount *ptr) {
1.74 + bool res = (subtle::Acquire_Load(ptr) == 0);
1.75 + if (res) {
1.76 + ANNOTATE_HAPPENS_AFTER(ptr);
1.77 + }
1.78 + return res;
1.79 +}
1.80 +
1.81 +} // namespace base
1.82 +
1.83 +#endif // BASE_ATOMIC_REF_COUNT_H_
