cefpython/src/include/base/cef_atomicops.h at cefpython49-winxp · pythonthings/cefpython · GitHub

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// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

// * Redistributions of source code must retain the above copyright

// notice, this list of conditions and the following disclaimer.

// * Redistributions in binary form must reproduce the above

// copyright notice, this list of conditions and the following disclaimer

// in the documentation and/or other materials provided with the

// distribution.

// * Neither the name of Google Inc. nor the name Chromium Embedded

// Framework nor the names of its contributors may be used to endorse

// or promote products derived from this software without specific prior

// written permission.

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// For atomic operations on reference counts, see cef_atomic_ref_count.h.

// The routines exported by this module are subtle. If you use them, even if

// you get the code right, it will depend on careful reasoning about atomicity

// and memory ordering; it will be less readable, and harder to maintain. If

// you plan to use these routines, you should have a good reason, such as solid

// evidence that performance would otherwise suffer, or there being no

// alternative. You should assume only properties explicitly guaranteed by the

// specifications in this file. You are almost certainly _not_ writing code

// just for the x86; if you assume x86 semantics, x86 hardware bugs and

// implementations on other archtectures will cause your code to break. If you

// do not know what you are doing, avoid these routines, and use a Mutex.

// It is incorrect to make direct assignments to/from an atomic variable.

// You should use one of the Load or Store routines. The NoBarrier

// versions are provided when no barriers are needed:

// NoBarrier_Store()

// NoBarrier_Load()

// Although there are currently no compiler enforcement, you are encouraged

// to use these.

#ifndef CEF_INCLUDE_BASE_CEF_ATOMICOPS_H_

#define CEF_INCLUDE_BASE_CEF_ATOMICOPS_H_

#pragma once

#if defined(BASE_ATOMICOPS_H_)

// Do nothing if the Chromium header has already been included.

// This can happen in cases where Chromium code is used directly by the

// client application. When using Chromium code directly always include

// the Chromium header first to avoid type conflicts.

#elif defined(BUILDING_CEF_SHARED)

// When building CEF include the Chromium header directly.

#include "base/atomicops.h"

#else // !BUILDING_CEF_SHARED

// The following is substantially similar to the Chromium implementation.

// If the Chromium implementation diverges the below implementation should be

// updated to match.

#include <stdint.h>

#include "include/base/cef_build.h"

#if defined(OS_WIN) && defined(ARCH_CPU_64_BITS)

// windows.h #defines this (only on x64). This causes problems because the

// public API also uses MemoryBarrier at the public name for this fence. So, on

// X64, undef it, and call its documented

// (http://msdn.microsoft.com/en-us/library/windows/desktop/ms684208.aspx)

// implementation directly.

#undef MemoryBarrier

#endif

namespace base {

namespace subtle {

typedef int32_t Atomic32;

#ifdef ARCH_CPU_64_BITS

// We need to be able to go between Atomic64 and AtomicWord implicitly. This

// means Atomic64 and AtomicWord should be the same type on 64-bit.

#if defined(__ILP32__) || defined(OS_NACL)

// NaCl's intptr_t is not actually 64-bits on 64-bit!

// http://code.google.com/p/nativeclient/issues/detail?id=1162

typedef int64_t Atomic64;

#else

typedef intptr_t Atomic64;

#endif

// Use AtomicWord for a machine-sized pointer. It will use the Atomic32 or

// Atomic64 routines below, depending on your architecture.

typedef intptr_t AtomicWord;

// Atomically execute:

// result = *ptr;

// if (*ptr == old_value)

// *ptr = new_value;

// return result;

// I.e., replace "*ptr" with "new_value" if "*ptr" used to be "old_value".

// Always return the old value of "*ptr"

// This routine implies no memory barriers.

Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,

Atomic32 old_value,

Atomic32 new_value);

// Atomically store new_value into *ptr, returning the previous value held in

// *ptr. This routine implies no memory barriers.

Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, Atomic32 new_value);

// Atomically increment *ptr by "increment". Returns the new value of

// *ptr with the increment applied. This routine implies no memory barriers.

Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, Atomic32 increment);

Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,

Atomic32 increment);

// These following lower-level operations are typically useful only to people

// implementing higher-level synchronization operations like spinlocks,

// mutexes, and condition-variables. They combine CompareAndSwap(), a load, or

// a store with appropriate memory-ordering instructions. "Acquire" operations

// ensure that no later memory access can be reordered ahead of the operation.

// "Release" operations ensure that no previous memory access can be reordered

// after the operation. "Barrier" operations have both "Acquire" and "Release"

// semantics. A MemoryBarrier() has "Barrier" semantics, but does no memory

// access.

Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,

Atomic32 old_value,

Atomic32 new_value);

Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,

Atomic32 old_value,

Atomic32 new_value);

void MemoryBarrier();

void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value);

void Acquire_Store(volatile Atomic32* ptr, Atomic32 value);

void Release_Store(volatile Atomic32* ptr, Atomic32 value);

Atomic32 NoBarrier_Load(volatile const Atomic32* ptr);

Atomic32 Acquire_Load(volatile const Atomic32* ptr);

Atomic32 Release_Load(volatile const Atomic32* ptr);

// 64-bit atomic operations (only available on 64-bit processors).

#ifdef ARCH_CPU_64_BITS

Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,

Atomic64 old_value,

Atomic64 new_value);

Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr, Atomic64 new_value);

Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment);

Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment);

Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,

Atomic64 old_value,

Atomic64 new_value);

Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,

Atomic64 old_value,

Atomic64 new_value);

void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value);

void Acquire_Store(volatile Atomic64* ptr, Atomic64 value);

void Release_Store(volatile Atomic64* ptr, Atomic64 value);

Atomic64 NoBarrier_Load(volatile const Atomic64* ptr);

Atomic64 Acquire_Load(volatile const Atomic64* ptr);

Atomic64 Release_Load(volatile const Atomic64* ptr);

#endif // ARCH_CPU_64_BITS

} // namespace subtle

} // namespace base

// Include our platform specific implementation.

#if defined(OS_WIN) && defined(COMPILER_MSVC) && defined(ARCH_CPU_X86_FAMILY)

#include "include/base/internal/cef_atomicops_x86_msvc.h"

#elif defined(OS_MACOSX)

#include "include/base/internal/cef_atomicops_mac.h"

#elif defined(COMPILER_GCC) && defined(ARCH_CPU_X86_FAMILY)

#include "include/base/internal/cef_atomicops_x86_gcc.h"

#else

#error "Atomic operations are not supported on your platform"

#endif

// On some platforms we need additional declarations to make

// AtomicWord compatible with our other Atomic* types.

#if defined(OS_MACOSX) || defined(OS_OPENBSD)

#include "include/base/internal/cef_atomicops_atomicword_compat.h"

#endif

#endif // !BUILDING_CEF_SHARED

#endif // CEF_INCLUDE_BASE_CEF_ATOMICOPS_H_

cefpython/src/include/base/cef_atomicops.h at cefpython49-winxp · pythonthings/cefpython · GitHub

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