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/*
* Copyright (C) 2008, 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 COMPUTER, INC. ``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 COMPUTER, INC. OR
* 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 StructureTransitionTable_h
#define StructureTransitionTable_h
#include "UString.h"
#include <wtf/HashFunctions.h>
#include <wtf/HashMap.h>
#include <wtf/HashTraits.h>
#include <wtf/OwnPtr.h>
#include <wtf/RefPtr.h>
namespace JSC {
class Structure;
class StructureTransitionTable {
static const intptr_t UsingSingleSlotFlag = 1;
struct Hash {
typedef std::pair<RefPtr<StringImpl>, unsigned> Key;
static unsigned hash(const Key& p)
{
return p.first->existingHash();
}
static bool equal(const Key& a, const Key& b)
{
return a == b;
}
static const bool safeToCompareToEmptyOrDeleted = true;
};
struct HashTraits {
typedef WTF::HashTraits<RefPtr<StringImpl> > FirstTraits;
typedef WTF::GenericHashTraits<unsigned> SecondTraits;
typedef std::pair<FirstTraits::TraitType, SecondTraits::TraitType > TraitType;
static const bool emptyValueIsZero = FirstTraits::emptyValueIsZero && SecondTraits::emptyValueIsZero;
static TraitType emptyValue() { return std::make_pair(FirstTraits::emptyValue(), SecondTraits::emptyValue()); }
static const bool needsDestruction = FirstTraits::needsDestruction || SecondTraits::needsDestruction;
static void constructDeletedValue(TraitType& slot) { FirstTraits::constructDeletedValue(slot.first); }
static bool isDeletedValue(const TraitType& value) { return FirstTraits::isDeletedValue(value.first); }
};
typedef HashMap<Hash::Key, Structure*, Hash, HashTraits> TransitionMap;
public:
StructureTransitionTable()
: m_data(UsingSingleSlotFlag)
{
}
~StructureTransitionTable()
{
if (!isUsingSingleSlot())
delete map();
}
inline void add(Structure*);
inline void remove(Structure*);
inline bool contains(StringImpl* rep, unsigned attributes) const;
inline Structure* get(StringImpl* rep, unsigned attributes) const;
private:
bool isUsingSingleSlot() const
{
return m_data & UsingSingleSlotFlag;
}
TransitionMap* map() const
{
ASSERT(!isUsingSingleSlot());
return reinterpret_cast<TransitionMap*>(m_data);
}
void setMap(TransitionMap* map)
{
ASSERT(isUsingSingleSlot());
// This implicitly clears the flag that indicates we're using a single transition
m_data = reinterpret_cast<intptr_t>(map);
ASSERT(!isUsingSingleSlot());
}
Structure* singleTransition() const
{
ASSERT(isUsingSingleSlot());
return reinterpret_cast<Structure*>(m_data & ~UsingSingleSlotFlag);
}
void setSingleTransition(Structure* structure)
{
ASSERT(isUsingSingleSlot());
m_data = reinterpret_cast<intptr_t>(structure) | UsingSingleSlotFlag;
}
intptr_t m_data;
};
} // namespace JSC
#endif // StructureTransitionTable_h
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