cefpython/src/include/base/cef_atomic_ref_count.h at cefpython51 · 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.

// This is a low level implementation of atomic semantics for reference

// counting. Please use cef_ref_counted.h directly instead.

// The Chromium implementation includes annotations to avoid some false

// positives when using data race detection tools. Annotations are not

// currently supported by the CEF implementation.

#ifndef CEF_INCLUDE_BASE_CEF_ATOMIC_REF_COUNT_H_

#define CEF_INCLUDE_BASE_CEF_ATOMIC_REF_COUNT_H_

#pragma once

#if defined(BASE_ATOMIC_REF_COUNT_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(USING_CHROMIUM_INCLUDES)

// When building CEF include the Chromium header directly.

#include "base/atomic_ref_count.h"

#else // !USING_CHROMIUM_INCLUDES

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

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

// updated to match.

#include "include/base/cef_atomicops.h"

// Annotations are not currently supported.

#define ANNOTATE_HAPPENS_BEFORE(obj) /* empty */

#define ANNOTATE_HAPPENS_AFTER(obj) /* empty */

namespace base {

typedef subtle::Atomic32 AtomicRefCount;

// Increment a reference count by "increment", which must exceed 0.

inline void AtomicRefCountIncN(volatile AtomicRefCount *ptr,

AtomicRefCount increment) {

subtle::NoBarrier_AtomicIncrement(ptr, increment);

}

// Decrement a reference count by "decrement", which must exceed 0,

// and return whether the result is non-zero.

// Insert barriers to ensure that state written before the reference count

// became zero will be visible to a thread that has just made the count zero.

inline bool AtomicRefCountDecN(volatile AtomicRefCount *ptr,

AtomicRefCount decrement) {

ANNOTATE_HAPPENS_BEFORE(ptr);

bool res = (subtle::Barrier_AtomicIncrement(ptr, -decrement) != 0);

if (!res) {

ANNOTATE_HAPPENS_AFTER(ptr);

}

return res;

}

// Increment a reference count by 1.

inline void AtomicRefCountInc(volatile AtomicRefCount *ptr) {

base::AtomicRefCountIncN(ptr, 1);

}

// Decrement a reference count by 1 and return whether the result is non-zero.

// Insert barriers to ensure that state written before the reference count

// became zero will be visible to a thread that has just made the count zero.

inline bool AtomicRefCountDec(volatile AtomicRefCount *ptr) {

return base::AtomicRefCountDecN(ptr, 1);

}

// Return whether the reference count is one. If the reference count is used

// in the conventional way, a refrerence count of 1 implies that the current

// thread owns the reference and no other thread shares it. This call performs

// the test for a reference count of one, and performs the memory barrier

// needed for the owning thread to act on the object, knowing that it has

// exclusive access to the object.

inline bool AtomicRefCountIsOne(volatile AtomicRefCount *ptr) {

bool res = (subtle::Acquire_Load(ptr) == 1);

if (res) {

ANNOTATE_HAPPENS_AFTER(ptr);

}

return res;

}

// Return whether the reference count is zero. With conventional object

// referencing counting, the object will be destroyed, so the reference count

// should never be zero. Hence this is generally used for a debug check.

inline bool AtomicRefCountIsZero(volatile AtomicRefCount *ptr) {

bool res = (subtle::Acquire_Load(ptr) == 0);

if (res) {

ANNOTATE_HAPPENS_AFTER(ptr);

}

return res;

}

} // namespace base

#endif // !USING_CHROMIUM_INCLUDES

#endif // CEF_INCLUDE_BASE_CEF_ATOMIC_REF_COUNT_H_

cefpython/src/include/base/cef_atomic_ref_count.h at cefpython51 · pythonthings/cefpython · GitHub

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