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/*
* Copyright (C) 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public License
* along with this library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
*/
#ifndef RefCounted_h
#define RefCounted_h
#include "wtf/FastAllocBase.h"
#include "wtf/InstanceCounter.h"
#include "wtf/Noncopyable.h"
#include "wtf/WTFExport.h"
#ifdef NDEBUG
#define CHECK_REF_COUNTED_LIFECYCLE 0
#else
#define CHECK_REF_COUNTED_LIFECYCLE 1
#include "wtf/Assertions.h"
#include "wtf/ThreadRestrictionVerifier.h"
#endif
namespace WTF {
// This base class holds the non-template methods and attributes.
// The RefCounted class inherits from it reducing the template bloat
// generated by the compiler (technique called template hoisting).
class WTF_EXPORT RefCountedBase {
public:
void ref()
{
#if CHECK_REF_COUNTED_LIFECYCLE
// Start thread verification as soon as the ref count gets to 2. This
// heuristic reflects the fact that items are often created on one thread
// and then given to another thread to be used.
// FIXME: Make this restriction tigher. Especially as we move to more
// common methods for sharing items across threads like CrossThreadCopier.h
// We should be able to add a "detachFromThread" method to make this explicit.
if (m_refCount == 1)
m_verifier.setShared(true);
// If this assert fires, it either indicates a thread safety issue or
// that the verification needs to change. See ThreadRestrictionVerifier for
// the different modes.
ASSERT(m_verifier.isSafeToUse());
ASSERT(!m_adoptionIsRequired);
#endif
ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun);
++m_refCount;
}
bool hasOneRef() const
{
ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun);
#if CHECK_REF_COUNTED_LIFECYCLE
ASSERT(m_verifier.isSafeToUse());
#endif
return m_refCount == 1;
}
int refCount() const
{
#if CHECK_REF_COUNTED_LIFECYCLE
ASSERT(m_verifier.isSafeToUse());
#endif
return m_refCount;
}
void relaxAdoptionRequirement()
{
ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun);
#if CHECK_REF_COUNTED_LIFECYCLE
ASSERT(m_adoptionIsRequired);
m_adoptionIsRequired = false;
#endif
}
protected:
RefCountedBase()
: m_refCount(1)
#if SECURITY_ASSERT_ENABLED
, m_deletionHasBegun(false)
#endif
#if CHECK_REF_COUNTED_LIFECYCLE
, m_adoptionIsRequired(true)
#endif
{
}
~RefCountedBase()
{
ASSERT_WITH_SECURITY_IMPLICATION(m_deletionHasBegun);
#if CHECK_REF_COUNTED_LIFECYCLE
ASSERT(!m_adoptionIsRequired);
#endif
}
// Returns whether the pointer should be freed or not.
bool derefBase()
{
ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun);
#if CHECK_REF_COUNTED_LIFECYCLE
ASSERT(m_verifier.isSafeToUse());
ASSERT(!m_adoptionIsRequired);
#endif
ASSERT(m_refCount > 0);
if (m_refCount == 1) {
#if SECURITY_ASSERT_ENABLED
m_deletionHasBegun = true;
#endif
return true;
}
--m_refCount;
#if CHECK_REF_COUNTED_LIFECYCLE
// Stop thread verification when the ref goes to 1 because it
// is safe to be passed to another thread at this point.
if (m_refCount == 1)
m_verifier.setShared(false);
#endif
return false;
}
#if CHECK_REF_COUNTED_LIFECYCLE
bool deletionHasBegun() const
{
return m_deletionHasBegun;
}
#endif
private:
#if CHECK_REF_COUNTED_LIFECYCLE || SECURITY_ASSERT_ENABLED
friend void adopted(RefCountedBase*);
#endif
int m_refCount;
#if SECURITY_ASSERT_ENABLED
bool m_deletionHasBegun;
#endif
#if CHECK_REF_COUNTED_LIFECYCLE
bool m_adoptionIsRequired;
ThreadRestrictionVerifier m_verifier;
#endif
};
#if CHECK_REF_COUNTED_LIFECYCLE || SECURITY_ASSERT_ENABLED
inline void adopted(RefCountedBase* object)
{
if (!object)
return;
ASSERT_WITH_SECURITY_IMPLICATION(!object->m_deletionHasBegun);
#if CHECK_REF_COUNTED_LIFECYCLE
object->m_adoptionIsRequired = false;
#endif
}
#endif
template<typename T> class RefCounted : public RefCountedBase {
WTF_MAKE_NONCOPYABLE(RefCounted);
WTF_MAKE_FAST_ALLOCATED;
public:
void deref()
{
if (derefBase())
delete static_cast<T*>(this);
}
protected:
#ifdef ENABLE_INSTANCE_COUNTER
RefCounted()
{
incrementInstanceCount<T>(static_cast<T*>(this));
}
~RefCounted()
{
decrementInstanceCount<T>(static_cast<T*>(this));
}
#else
RefCounted()
{
}
#endif
};
} // namespace WTF
using WTF::RefCounted;
#endif // RefCounted_h
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