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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/PtrAndFlags.h>
#include <wtf/OwnPtr.h>
#include <wtf/RefPtr.h>
namespace JSC {
class Structure;
struct StructureTransitionTableHash {
typedef std::pair<RefPtr<UString::Rep>, 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 StructureTransitionTableHashTraits {
typedef WTF::HashTraits<RefPtr<UString::Rep> > 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); }
};
class StructureTransitionTable {
typedef std::pair<Structure*, Structure*> Transition;
struct TransitionTable : public HashMap<StructureTransitionTableHash::Key, Transition, StructureTransitionTableHash, StructureTransitionTableHashTraits> {
typedef HashMap<unsigned, Structure*> AnonymousSlotMap;
void addSlotTransition(unsigned count, Structure* structure)
{
ASSERT(!getSlotTransition(count));
if (!m_anonymousSlotTable)
m_anonymousSlotTable.set(new AnonymousSlotMap);
m_anonymousSlotTable->add(count, structure);
}
void removeSlotTransition(unsigned count)
{
ASSERT(getSlotTransition(count));
m_anonymousSlotTable->remove(count);
}
Structure* getSlotTransition(unsigned count)
{
if (!m_anonymousSlotTable)
return 0;
AnonymousSlotMap::iterator find = m_anonymousSlotTable->find(count);
if (find == m_anonymousSlotTable->end())
return 0;
return find->second;
}
private:
OwnPtr<AnonymousSlotMap> m_anonymousSlotTable;
};
public:
StructureTransitionTable() {
m_transitions.m_singleTransition.set(0);
m_transitions.m_singleTransition.setFlag(usingSingleSlot);
}
~StructureTransitionTable() {
if (!usingSingleTransitionSlot())
delete table();
}
// The contains and get methods accept imprecise matches, so if an unspecialised transition exists
// for the given key they will consider that transition to be a match. If a specialised transition
// exists and it matches the provided specificValue, get will return the specific transition.
inline bool contains(const StructureTransitionTableHash::Key&, JSCell* specificValue);
inline Structure* get(const StructureTransitionTableHash::Key&, JSCell* specificValue) const;
inline bool hasTransition(const StructureTransitionTableHash::Key& key) const;
void remove(const StructureTransitionTableHash::Key& key, JSCell* specificValue)
{
if (usingSingleTransitionSlot()) {
ASSERT(contains(key, specificValue));
setSingleTransition(0);
return;
}
TransitionTable::iterator find = table()->find(key);
if (!specificValue)
find->second.first = 0;
else
find->second.second = 0;
if (!find->second.first && !find->second.second)
table()->remove(find);
}
void add(const StructureTransitionTableHash::Key& key, Structure* structure, JSCell* specificValue)
{
if (usingSingleTransitionSlot()) {
if (!singleTransition()) {
setSingleTransition(structure);
return;
}
reifySingleTransition();
}
if (!specificValue) {
TransitionTable::iterator find = table()->find(key);
if (find == table()->end())
table()->add(key, Transition(structure, (Structure*)0));
else
find->second.first = structure;
} else {
// If we're adding a transition to a specific value, then there cannot be
// an existing transition
ASSERT(!table()->contains(key));
table()->add(key, Transition((Structure*)0, structure));
}
}
Structure* getAnonymousSlotTransition(unsigned count)
{
if (usingSingleTransitionSlot())
return 0;
return table()->getSlotTransition(count);
}
void addAnonymousSlotTransition(unsigned count, Structure* structure)
{
if (usingSingleTransitionSlot())
reifySingleTransition();
ASSERT(!table()->getSlotTransition(count));
table()->addSlotTransition(count, structure);
}
void removeAnonymousSlotTransition(unsigned count)
{
ASSERT(!usingSingleTransitionSlot());
table()->removeSlotTransition(count);
}
private:
TransitionTable* table() const { ASSERT(!usingSingleTransitionSlot()); return m_transitions.m_table; }
Structure* singleTransition() const {
ASSERT(usingSingleTransitionSlot());
return m_transitions.m_singleTransition.get();
}
bool usingSingleTransitionSlot() const { return m_transitions.m_singleTransition.isFlagSet(usingSingleSlot); }
void setSingleTransition(Structure* structure)
{
ASSERT(usingSingleTransitionSlot());
m_transitions.m_singleTransition.set(structure);
}
void setTransitionTable(TransitionTable* table)
{
ASSERT(usingSingleTransitionSlot());
#ifndef NDEBUG
setSingleTransition(0);
#endif
m_transitions.m_table = table;
// This implicitly clears the flag that indicates we're using a single transition
ASSERT(!usingSingleTransitionSlot());
}
inline void reifySingleTransition();
enum UsingSingleSlot {
usingSingleSlot
};
// Last bit indicates whether we are using the single transition optimisation
union {
TransitionTable* m_table;
PtrAndFlagsBase<Structure, UsingSingleSlot> m_singleTransition;
} m_transitions;
};
} // namespace JSC
#endif // StructureTransitionTable_h
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