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
149 lines
6.4 KiB
C++
149 lines
6.4 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_H_
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#define WEBRTC_SYSTEM_WRAPPERS_INTERFACE_ATOMICOPS_H_
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#if defined(_MSC_VER)
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#include <stddef.h> /* intptr_t */
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#endif
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#include "typedefs.h"
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namespace webrtc {
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// Extracted from Chromium's src/base/atomicops.h.
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//
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// The routines exported by this module are subtle. If you use them, even if
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// you get the code right, it will depend on careful reasoning about atomicity
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// and memory ordering; it will be less readable, and harder to maintain. If
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// you plan to use these routines, you should have a good reason, such as solid
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// evidence that performance would otherwise suffer, or there being no
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// alternative. You should assume only properties explicitly guaranteed by the
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// specifications in this file. You are almost certainly _not_ writing code
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// just for the x86; if you assume x86 semantics, x86 hardware bugs and
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// implementations on other archtectures will cause your code to break. If you
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// do not know what you are doing, avoid these routines, and use a Mutex.
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//
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// It is incorrect to make direct assignments to/from an atomic variable.
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// You should use one of the Load or Store routines. The NoBarrier
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// versions are provided when no barriers are needed:
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// NoBarrier_Store()
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// NoBarrier_Load()
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// Although there are currently no compiler enforcement, you are encouraged
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// to use these.
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//
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namespace subtle {
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typedef int32_t Atomic32;
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#ifdef WEBRTC_ARCH_64_BITS
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typedef intptr_t Atomic64;
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#endif // WEBRTC_ARCH_64_BITS
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// Use AtomicWord for a machine-sized pointer. It will use the Atomic32 or
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// Atomic64 routines below, depending on your architecture.
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typedef intptr_t AtomicWord;
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// Atomically execute:
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// result = *ptr;
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// if (*ptr == old_value)
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// *ptr = new_value;
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// return result;
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//
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// I.e., replace "*ptr" with "new_value" if "*ptr" used to be "old_value".
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// Always return the old value of "*ptr"
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//
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// This routine implies no memory barriers.
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Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
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Atomic32 old_value,
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Atomic32 new_value);
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// Atomically store new_value into *ptr, returning the previous value held in
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// *ptr. This routine implies no memory barriers.
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Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, Atomic32 new_value);
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// Atomically increment *ptr by "increment". Returns the new value of
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// *ptr with the increment applied. This routine implies no memory barriers.
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Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, Atomic32 increment);
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Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
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Atomic32 increment);
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// These following lower-level operations are typically useful only to people
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// implementing higher-level synchronization operations like spinlocks,
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// mutexes, and condition-variables. They combine CompareAndSwap(), a load, or
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// a store with appropriate memory-ordering instructions. "Acquire" operations
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// ensure that no later memory access can be reordered ahead of the operation.
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// "Release" operations ensure that no previous memory access can be reordered
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// after the operation. "Barrier" operations have both "Acquire" and "Release"
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// semantics. A MemoryBarrier() has "Barrier" semantics, but does no memory
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// access.
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Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
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Atomic32 old_value,
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Atomic32 new_value);
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Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
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Atomic32 old_value,
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Atomic32 new_value);
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void MemoryBarrier();
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void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value);
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void Acquire_Store(volatile Atomic32* ptr, Atomic32 value);
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void Release_Store(volatile Atomic32* ptr, Atomic32 value);
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Atomic32 NoBarrier_Load(volatile const Atomic32* ptr);
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Atomic32 Acquire_Load(volatile const Atomic32* ptr);
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Atomic32 Release_Load(volatile const Atomic32* ptr);
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// 64-bit atomic operations (only available on 64-bit processors).
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#ifdef WEBRTC_ARCH_64_BITS
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Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
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Atomic64 old_value,
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Atomic64 new_value);
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Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr, Atomic64 new_value);
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Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment);
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Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment);
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Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
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Atomic64 old_value,
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Atomic64 new_value);
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Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
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Atomic64 old_value,
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Atomic64 new_value);
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void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value);
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void Acquire_Store(volatile Atomic64* ptr, Atomic64 value);
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void Release_Store(volatile Atomic64* ptr, Atomic64 value);
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Atomic64 NoBarrier_Load(volatile const Atomic64* ptr);
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Atomic64 Acquire_Load(volatile const Atomic64* ptr);
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Atomic64 Release_Load(volatile const Atomic64* ptr);
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#endif // WEBRTC_ARCH_64_BITS
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} // namespace webrtc::subtle
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} // namespace webrtc
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// Include our platform specific implementation.
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#if defined(WEBRTC_WIN) && defined(_MSC_VER) && defined(WEBRTC_ARCH_X86_FAMILY)
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#include "webrtc/system_wrappers/interface/atomicops_internals_x86_msvc.h"
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#elif defined(WEBRTC_MAC)
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#include "webrtc/system_wrappers/interface/atomicops_internals_mac.h"
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#elif defined(__GNUC__) && defined(__ARMEL__)
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#include "webrtc/system_wrappers/interface/atomicops_internals_gcc.h"
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#elif defined(__GNUC__) && defined(WEBRTC_ARCH_X86_FAMILY)
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#include "webrtc/system_wrappers/interface/atomicops_internals_x86_gcc.h"
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#elif defined(__GNUC__) && defined(__MIPSEL__)
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#include "webrtc/system_wrappers/interface/atomicops_internals_mips_gcc.h"
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#else
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#error "Atomic operations are not supported on your platform"
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#endif
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// On some platforms we need additional declarations to make
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// AtomicWord compatible with our other Atomic* types.
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#if defined(WEBRTC_MAC) || defined(__OpenBSD__)
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#include "webrtc/system_wrappers/interface/atomicops_internals_atomicword_compat.h"
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#endif
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#endif // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_ATOMICOPS_H_
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