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/*
* Copyright (C) 2007, 2008, 2010 Apple Inc. All rights reserved.
* Copyright (C) 2007 Justin Haygood (jhaygood@reaktix.com)
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. Neither the name of Apple Computer, Inc. ("Apple") 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 APPLE AND ITS 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 APPLE OR ITS 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.
*
*
* Note: The implementations of InterlockedIncrement and InterlockedDecrement are based
* on atomic_increment and atomic_exchange_and_add from the Boost C++ Library. The license
* is virtually identical to the Apple license above but is included here for completeness.
*
* Boost Software License - Version 1.0 - August 17th, 2003
*
* Permission is hereby granted, free of charge, to any person or organization
* obtaining a copy of the software and accompanying documentation covered by
* this license (the "Software") to use, reproduce, display, distribute,
* execute, and transmit the Software, and to prepare derivative works of the
* Software, and to permit third-parties to whom the Software is furnished to
* do so, all subject to the following:
*
* The copyright notices in the Software and this entire statement, including
* the above license grant, this restriction and the following disclaimer,
* must be included in all copies of the Software, in whole or in part, and
* all derivative works of the Software, unless such copies or derivative
* works are solely in the form of machine-executable object code generated by
* a source language processor.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
* SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
* FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#ifndef ThreadSafeShared_h
#define ThreadSafeShared_h
#include "Platform.h"
#include <wtf/Atomics.h>
#include <wtf/ThreadingPrimitives.h>
namespace WTF {
class ThreadSafeSharedBase {
WTF_MAKE_NONCOPYABLE(ThreadSafeSharedBase); WTF_MAKE_FAST_ALLOCATED;
public:
ThreadSafeSharedBase(int initialRefCount = 1)
: m_refCount(initialRefCount)
{
}
void ref()
{
#if USE(LOCKFREE_THREADSAFESHARED)
atomicIncrement(&m_refCount);
#else
MutexLocker locker(m_mutex);
++m_refCount;
#endif
}
bool hasOneRef()
{
return refCount() == 1;
}
int refCount() const
{
#if !USE(LOCKFREE_THREADSAFESHARED)
MutexLocker locker(m_mutex);
#endif
return static_cast<int const volatile &>(m_refCount);
}
protected:
// Returns whether the pointer should be freed or not.
bool derefBase()
{
#if USE(LOCKFREE_THREADSAFESHARED)
if (atomicDecrement(&m_refCount) <= 0)
return true;
#else
int refCount;
{
MutexLocker locker(m_mutex);
--m_refCount;
refCount = m_refCount;
}
if (refCount <= 0)
return true;
#endif
return false;
}
private:
template<class T>
friend class CrossThreadRefCounted;
int m_refCount;
#if !USE(LOCKFREE_THREADSAFESHARED)
mutable Mutex m_mutex;
#endif
};
template<class T> class ThreadSafeShared : public ThreadSafeSharedBase {
public:
void deref()
{
if (derefBase())
delete static_cast<T*>(this);
}
protected:
ThreadSafeShared()
{
}
};
} // namespace WTF
using WTF::ThreadSafeShared;
#endif // ThreadSafeShared_h
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