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/*
* Copyright (C) 2010 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 GCHandle_h
#define GCHandle_h
#include <wtf/Assertions.h>
namespace JSC {
class Heap;
class JSCell;
class WeakGCHandle;
class WeakGCHandlePool;
class WeakGCHandle {
friend class WeakGCHandlePool;
public:
// Because JSCell objects are aligned, we can use the lower two bits as
// status flags. The least significant bit is set when the handle is not a
// pointer, i.e. when it's used as a offset for the free list in
// WeakGCHandlePool. The second least significant bit is set when the object
// the pointer corresponds to has been deleted by a garbage collection
bool isValidPtr() { return !(m_ptr & 3); }
bool isPtr() { return !(m_ptr & 1); }
bool isNext() { return (m_ptr & 3) == 1; }
void invalidate()
{
ASSERT(isValidPtr());
m_ptr |= 2;
}
JSCell* get()
{
ASSERT(isPtr());
return reinterpret_cast<JSCell*>(m_ptr & ~3);
}
void set(JSCell* p)
{
m_ptr = reinterpret_cast<uintptr_t>(p);
ASSERT(isPtr());
}
WeakGCHandlePool* pool();
private:
uintptr_t getNextInFreeList()
{
ASSERT(isNext());
return m_ptr >> 2;
}
void setNextInFreeList(uintptr_t n)
{
m_ptr = (n << 2) | 1;
ASSERT(isNext());
}
uintptr_t m_ptr;
};
class WeakGCHandlePool {
public:
static const size_t poolSize = 32 * 1024; // 32k
static const size_t poolMask = ~(poolSize - 1);
static const size_t numPoolEntries = (poolSize - sizeof(Heap*) - 3 * sizeof(unsigned)) / sizeof(WeakGCHandle);
WeakGCHandlePool();
WeakGCHandle* allocate(JSCell* cell);
void free(WeakGCHandle*);
bool isFull()
{
ASSERT(m_entriesSize < WeakGCHandlePool::numPoolEntries);
return m_entriesSize == WeakGCHandlePool::numPoolEntries - 1;
}
void update();
private:
Heap* m_heap;
unsigned m_entriesSize;
unsigned m_initialAlloc;
WeakGCHandle m_entries[WeakGCHandlePool::numPoolEntries];
};
}
#endif
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