1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/ipc/chromium/src/base/atomic_ref_count.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,63 @@
1.4 +// Copyright (c) 2006-2008 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/ref_counted.h directly instead.
1.10 +
1.11 +#ifndef BASE_ATOMIC_REF_COUNT_H_
1.12 +#define BASE_ATOMIC_REF_COUNT_H_
1.13 +
1.14 +#include "base/atomicops.h"
1.15 +
1.16 +namespace base {
1.17 +
1.18 +typedef subtle::Atomic32 AtomicRefCount;
1.19 +
1.20 +// Increment a reference count by "increment", which must exceed 0.
1.21 +inline void AtomicRefCountIncN(volatile AtomicRefCount *ptr,
1.22 + AtomicRefCount increment) {
1.23 + subtle::NoBarrier_AtomicIncrement(ptr, increment);
1.24 +}
1.25 +
1.26 +// Decrement a reference count by "decrement", which must exceed 0,
1.27 +// and return whether the result is non-zero.
1.28 +// Insert barriers to ensure that state written before the reference count
1.29 +// became zero will be visible to a thread that has just made the count zero.
1.30 +inline bool AtomicRefCountDecN(volatile AtomicRefCount *ptr,
1.31 + AtomicRefCount decrement) {
1.32 + return subtle::Barrier_AtomicIncrement(ptr, -decrement) != 0;
1.33 +}
1.34 +
1.35 +// Increment a reference count by 1.
1.36 +inline void AtomicRefCountInc(volatile AtomicRefCount *ptr) {
1.37 + base::AtomicRefCountIncN(ptr, 1);
1.38 +}
1.39 +
1.40 +// Decrement a reference count by 1 and return whether the result is non-zero.
1.41 +// Insert barriers to ensure that state written before the reference count
1.42 +// became zero will be visible to a thread that has just made the count zero.
1.43 +inline bool AtomicRefCountDec(volatile AtomicRefCount *ptr) {
1.44 + return base::AtomicRefCountDecN(ptr, 1);
1.45 +}
1.46 +
1.47 +// Return whether the reference count is one. If the reference count is used
1.48 +// in the conventional way, a refrerence count of 1 implies that the current
1.49 +// thread owns the reference and no other thread shares it. This call performs
1.50 +// the test for a reference count of one, and performs the memory barrier
1.51 +// needed for the owning thread to act on the object, knowing that it has
1.52 +// exclusive access to the object.
1.53 +inline bool AtomicRefCountIsOne(volatile AtomicRefCount *ptr) {
1.54 + return subtle::Acquire_Load(ptr) == 1;
1.55 +}
1.56 +
1.57 +// Return whether the reference count is zero. With conventional object
1.58 +// referencing counting, the object will be destroyed, so the reference count
1.59 +// should never be zero. Hence this is generally used for a debug check.
1.60 +inline bool AtomicRefCountIsZero(volatile AtomicRefCount *ptr) {
1.61 + return subtle::Acquire_Load(ptr) == 0;
1.62 +}
1.63 +
1.64 +} // namespace base
1.65 +
1.66 +#endif // BASE_ATOMIC_REF_COUNT_H_
