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/*
* Copyright (C) 2009 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 WeakGCMap_h
#define WeakGCMap_h
#include "Heap.h"
#include <wtf/HashMap.h>
namespace JSC {
class JSCell;
// A HashMap whose get() function returns emptyValue() for cells awaiting destruction.
template<typename KeyType, typename MappedType>
class WeakGCMap {
WTF_MAKE_FAST_ALLOCATED;
/*
Invariants:
* A value enters the WeakGCMap marked. (Guaranteed by set().)
* A value that becomes unmarked leaves the WeakGCMap before being recycled. (Guaranteed by the value's destructor removing it from the WeakGCMap.)
* A value that becomes unmarked leaves the WeakGCMap before becoming marked again. (Guaranteed by all destructors running before the mark phase begins.)
* During the mark phase, all values in the WeakGCMap are valid. (Guaranteed by all destructors running before the mark phase begins.)
*/
public:
typedef typename HashMap<KeyType, DeprecatedPtr<MappedType> >::iterator iterator;
typedef typename HashMap<KeyType, DeprecatedPtr<MappedType> >::const_iterator const_iterator;
bool isEmpty() { return m_map.isEmpty(); }
void clear() { m_map.clear(); }
MappedType* get(const KeyType&) const;
pair<iterator, bool> set(const KeyType&, MappedType*);
MappedType* take(const KeyType&);
// These unchecked functions provide access to a value even if the value's
// mark bit is not set. This is used, among other things, to retrieve values
// during the GC mark phase, which begins by clearing all mark bits.
size_t uncheckedSize() { return m_map.size(); }
MappedType* uncheckedGet(const KeyType& key) const { return m_map.get(key).get(); }
DeprecatedPtr<MappedType>* uncheckedGetSlot(const KeyType& key)
{
iterator iter = m_map.find(key);
if (iter == m_map.end())
return 0;
return &iter->second;
}
bool uncheckedRemove(const KeyType&, MappedType*);
iterator uncheckedBegin() { return m_map.begin(); }
iterator uncheckedEnd() { return m_map.end(); }
const_iterator uncheckedBegin() const { return m_map.begin(); }
const_iterator uncheckedEnd() const { return m_map.end(); }
bool isValid(iterator it) const { return Heap::isMarked(it->second.get()); }
bool isValid(const_iterator it) const { return Heap::isMarked(it->second.get()); }
private:
HashMap<KeyType, DeprecatedPtr<MappedType> > m_map;
};
template<typename KeyType, typename MappedType>
inline MappedType* WeakGCMap<KeyType, MappedType>::get(const KeyType& key) const
{
MappedType* result = m_map.get(key).get();
if (result == HashTraits<MappedType*>::emptyValue())
return result;
if (!Heap::isMarked(result))
return HashTraits<MappedType*>::emptyValue();
return result;
}
template<typename KeyType, typename MappedType>
MappedType* WeakGCMap<KeyType, MappedType>::take(const KeyType& key)
{
MappedType* result = m_map.take(key).get();
if (result == HashTraits<MappedType*>::emptyValue())
return result;
if (!Heap::isMarked(result))
return HashTraits<MappedType*>::emptyValue();
return result;
}
template<typename KeyType, typename MappedType>
pair<typename WeakGCMap<KeyType, MappedType>::iterator, bool> WeakGCMap<KeyType, MappedType>::set(const KeyType& key, MappedType* value)
{
Heap::setMarked(value); // If value is newly allocated, it's not marked, so mark it now.
pair<iterator, bool> result = m_map.add(key, value);
if (!result.second) { // pre-existing entry
result.second = !Heap::isMarked(result.first->second.get());
result.first->second = value;
}
return result;
}
template<typename KeyType, typename MappedType>
bool WeakGCMap<KeyType, MappedType>::uncheckedRemove(const KeyType& key, MappedType* value)
{
iterator it = m_map.find(key);
if (it == m_map.end())
return false;
if (it->second.get() != value)
return false;
m_map.remove(it);
return true;
}
} // namespace JSC
#endif // WeakGCMap_h
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