81cffd1f2c
Porting Chromium's base/atomicops.h and friends into WebRTC. Included the original unit test in Chromium. Review URL: https://webrtc-codereview.appspot.com/964026 git-svn-id: http://webrtc.googlecode.com/svn/trunk@3241 4adac7df-926f-26a2-2b94-8c16560cd09d
109 lines
3.4 KiB
C++
109 lines
3.4 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file under third_party_mods/chromium or at:
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// http://src.chromium.org/svn/trunk/src/LICENSE
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#ifndef WEBRTC_SYSTEM_WRAPPERS_INTERFACE_ATOMICOPS_INTERNALS_GCC_H_
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#define WEBRTC_SYSTEM_WRAPPERS_INTERFACE_ATOMICOPS_INTERNALS_GCC_H_
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// Extracted from Chromium's src/base/atomicops_internals_gcc.h.
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// This file is an internal atomic implementation, include atomicops.h
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// instead. This file is for platforms that use GCC intrinsics rather than
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// platform-specific assembly code for atomic operations.
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namespace webrtc {
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namespace subtle {
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inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
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Atomic32 old_value,
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Atomic32 new_value) {
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Atomic32 prev_value;
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do {
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if (__sync_bool_compare_and_swap(ptr, old_value, new_value))
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return old_value;
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prev_value = *ptr;
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} while (prev_value == old_value);
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return prev_value;
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}
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inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
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Atomic32 new_value) {
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Atomic32 old_value;
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do {
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old_value = *ptr;
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} while (!__sync_bool_compare_and_swap(ptr, old_value, new_value));
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return old_value;
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}
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inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
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Atomic32 increment) {
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return Barrier_AtomicIncrement(ptr, increment);
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}
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inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
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Atomic32 increment) {
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for (;;) {
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// Atomic exchange the old value with an incremented one.
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Atomic32 old_value = *ptr;
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Atomic32 new_value = old_value + increment;
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if (__sync_bool_compare_and_swap(ptr, old_value, new_value)) {
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// The exchange took place as expected.
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return new_value;
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}
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// Otherwise, *ptr changed mid-loop and we need to retry.
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}
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}
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inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
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Atomic32 old_value,
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Atomic32 new_value) {
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// Since NoBarrier_CompareAndSwap uses __sync_bool_compare_and_swap, which
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// is a full memory barrier, none is needed here or below in Release.
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return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
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}
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inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
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Atomic32 old_value,
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Atomic32 new_value) {
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return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
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}
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inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
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*ptr = value;
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}
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inline void MemoryBarrier() {
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__sync_synchronize();
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}
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inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
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*ptr = value;
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MemoryBarrier();
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}
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inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
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MemoryBarrier();
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*ptr = value;
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}
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inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
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return *ptr;
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}
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inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
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Atomic32 value = *ptr;
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MemoryBarrier();
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return value;
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}
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inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
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MemoryBarrier();
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return *ptr;
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}
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} // namespace webrtc::subtle
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} // namespace webrtc
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#endif // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_ATOMICOPS_INTERNALS_GCC_H_
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