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/*
* Copyright (C) 2013 Apple Inc. All rights reserved.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 INC. 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.
*/
#ifndef DeferrableRefCounted_h
#define DeferrableRefCounted_h
#include <wtf/Assertions.h>
#include <wtf/FastMalloc.h>
#include <wtf/Noncopyable.h>
namespace WTF {
// A variant of RefCounted that allows reference counting to be deferred,
// and can tell you if that has happened. You can think of a deferral as
// just being an additional "ref", except that you can detect if it has
// specifically happened - this can be useful either for debugging, or
// sometimes even for some additional functionality.
class DeferrableRefCountedBase {
static const unsigned deferredFlag = 1;
static const unsigned normalIncrement = 2;
public:
void ref()
{
m_refCount += normalIncrement;
}
bool hasOneRef() const
{
return refCount() == 1;
}
unsigned refCount() const
{
return m_refCount / normalIncrement;
}
bool isDeferred() const
{
return !!(m_refCount & deferredFlag);
}
protected:
DeferrableRefCountedBase()
: m_refCount(normalIncrement)
{
}
~DeferrableRefCountedBase()
{
}
bool derefBase()
{
m_refCount -= normalIncrement;
return !m_refCount;
}
bool setIsDeferredBase(bool value)
{
if (value) {
m_refCount |= deferredFlag;
return false;
}
m_refCount &= ~deferredFlag;
return !m_refCount;
}
private:
unsigned m_refCount;
};
template<typename T>
class DeferrableRefCounted : public DeferrableRefCountedBase {
WTF_MAKE_NONCOPYABLE(DeferrableRefCounted); WTF_MAKE_FAST_ALLOCATED;
public:
void deref()
{
if (derefBase())
delete static_cast<T*>(this);
}
bool setIsDeferred(bool value)
{
if (!setIsDeferredBase(value))
return false;
delete static_cast<T*>(this);
return true;
}
protected:
DeferrableRefCounted() { }
~DeferrableRefCounted() { }
};
} // namespace WTF
using WTF::DeferrableRefCounted;
#endif // DeferrableRefCounted_h
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