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/*
* Copyright (C) 2012 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. 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 INC. 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.
*/
#ifndef WeakBlock_h
#define WeakBlock_h
#include "HeapBlock.h"
#include "WeakHandleOwner.h"
#include "WeakImpl.h"
#include <wtf/DoublyLinkedList.h>
#include <wtf/StdLibExtras.h>
namespace JSC {
class DeadBlock;
class HeapRootVisitor;
class JSValue;
class WeakHandleOwner;
class WeakBlock : public HeapBlock<WeakBlock> {
public:
friend class WTF::DoublyLinkedListNode<WeakBlock>;
static const size_t blockSize = 4 * KB; // 5% of MarkedBlock size
struct FreeCell {
FreeCell* next;
};
struct SweepResult {
SweepResult();
bool isNull() const;
bool blockIsFree;
FreeCell* freeList;
};
static WeakBlock* create(DeadBlock*);
static WeakImpl* asWeakImpl(FreeCell*);
bool isEmpty();
void sweep();
SweepResult takeSweepResult();
void visit(HeapRootVisitor&);
void reap();
void lastChanceToFinalize();
private:
static FreeCell* asFreeCell(WeakImpl*);
WeakBlock(Region*);
WeakImpl* firstWeakImpl();
void finalize(WeakImpl*);
WeakImpl* weakImpls();
size_t weakImplCount();
void addToFreeList(FreeCell**, WeakImpl*);
SweepResult m_sweepResult;
};
inline WeakBlock::SweepResult::SweepResult()
: blockIsFree(true)
, freeList(0)
{
ASSERT(isNull());
}
inline bool WeakBlock::SweepResult::isNull() const
{
return blockIsFree && !freeList; // This state is impossible, so we can use it to mean null.
}
inline WeakImpl* WeakBlock::asWeakImpl(FreeCell* freeCell)
{
return reinterpret_cast_ptr<WeakImpl*>(freeCell);
}
inline WeakBlock::SweepResult WeakBlock::takeSweepResult()
{
SweepResult tmp;
std::swap(tmp, m_sweepResult);
ASSERT(m_sweepResult.isNull());
return tmp;
}
inline WeakBlock::FreeCell* WeakBlock::asFreeCell(WeakImpl* weakImpl)
{
return reinterpret_cast_ptr<FreeCell*>(weakImpl);
}
inline WeakImpl* WeakBlock::weakImpls()
{
return reinterpret_cast_ptr<WeakImpl*>(this) + ((sizeof(WeakBlock) + sizeof(WeakImpl) - 1) / sizeof(WeakImpl));
}
inline size_t WeakBlock::weakImplCount()
{
return (blockSize / sizeof(WeakImpl)) - ((sizeof(WeakBlock) + sizeof(WeakImpl) - 1) / sizeof(WeakImpl));
}
inline void WeakBlock::addToFreeList(FreeCell** freeList, WeakImpl* weakImpl)
{
ASSERT(weakImpl->state() == WeakImpl::Deallocated);
FreeCell* freeCell = asFreeCell(weakImpl);
ASSERT(!*freeList || ((char*)*freeList > (char*)this && (char*)*freeList < (char*)this + blockSize));
ASSERT((char*)freeCell > (char*)this && (char*)freeCell < (char*)this + blockSize);
freeCell->next = *freeList;
*freeList = freeCell;
}
inline bool WeakBlock::isEmpty()
{
return !m_sweepResult.isNull() && m_sweepResult.blockIsFree;
}
} // namespace JSC
#endif // WeakBlock_h
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