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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/Weak.h>
#include <heap/WeakInlines.h>
#include <wtf/HashMap.h>
namespace JSC {
// A HashMap with Weak<JSCell> values, which automatically removes values once they're garbage collected.
template<typename KeyArg, typename RawMappedArg, typename HashArg = typename DefaultHash<KeyArg>::Hash,
typename KeyTraitsArg = HashTraits<KeyArg> >
class WeakGCMap : public HashMap<KeyArg, Weak<RawMappedArg>, HashArg, KeyTraitsArg> {
typedef Weak<RawMappedArg> MappedType;
typedef HashMap<KeyArg, MappedType, HashArg, KeyTraitsArg> Base;
typedef WeakGCMap<KeyArg, RawMappedArg, HashArg, KeyTraitsArg> Self;
typedef HashTraits<MappedType> MappedTraits;
typedef typename MappedTraits::PassInType MappedPassInType;
public:
typedef typename Base::KeyType KeyType;
typedef typename Base::AddResult AddResult;
typedef typename Base::iterator iterator;
typedef typename Base::const_iterator const_iterator;
using Base::begin;
using Base::end;
using Base::size;
using Base::remove;
WeakGCMap()
: m_gcThreshold(minGCThreshold)
{
}
AddResult set(const KeyType& key, MappedPassInType value)
{
gcMapIfNeeded();
return Base::set(key, value);
}
AddResult add(const KeyType& key, MappedPassInType value)
{
gcMapIfNeeded();
AddResult addResult = Base::add(key, nullptr);
if (!addResult.iterator->value) { // New value or found a zombie value.
addResult.isNewEntry = true;
addResult.iterator->value = value;
}
return addResult;
}
iterator find(const KeyType& key)
{
iterator it = Base::find(key);
iterator end = Base::end();
if (it != end && !it->value) // Found a zombie value.
return end;
return it;
}
const_iterator find(const KeyType& key) const
{
return const_cast<Self*>(this)->find(key);
}
bool contains(const KeyType& key) const
{
return find(key) != end();
}
private:
static const int minGCThreshold = 3;
void gcMap()
{
Vector<KeyType, 4> zombies;
iterator end = this->end();
for (iterator it = begin(); it != end; ++it) {
if (!it->value)
zombies.append(it->key);
}
for (size_t i = 0; i < zombies.size(); ++i)
remove(zombies[i]);
}
void gcMapIfNeeded()
{
if (size() < m_gcThreshold)
return;
gcMap();
m_gcThreshold = std::max(minGCThreshold, size() * 2 - 1);
}
int m_gcThreshold;
};
template<typename KeyArg, typename RawMappedArg, typename HashArg, typename KeyTraitsArg>
const int WeakGCMap<KeyArg, RawMappedArg, HashArg, KeyTraitsArg>::minGCThreshold;
} // namespace JSC
#endif // WeakGCMap_h
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