| /* |
| * 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 "Collector.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 : public FastAllocBase { |
| /* |
| 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, MappedType>::iterator iterator; |
| typedef typename HashMap<KeyType, MappedType>::const_iterator const_iterator; |
| |
| bool isEmpty() { return m_map.isEmpty(); } |
| |
| MappedType get(const KeyType& key) const; |
| pair<iterator, bool> set(const KeyType&, const MappedType&); |
| MappedType take(const KeyType& key); |
| |
| // 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. |
| |
| MappedType uncheckedGet(const KeyType& key) const { return m_map.get(key); } |
| bool uncheckedRemove(const KeyType&, const 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(); } |
| |
| private: |
| HashMap<KeyType, MappedType> m_map; |
| }; |
| |
| template<typename KeyType, typename MappedType> |
| inline MappedType WeakGCMap<KeyType, MappedType>::get(const KeyType& key) const |
| { |
| MappedType result = m_map.get(key); |
| if (result == HashTraits<MappedType>::emptyValue()) |
| return result; |
| if (!Heap::isCellMarked(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); |
| if (result == HashTraits<MappedType>::emptyValue()) |
| return result; |
| if (!Heap::isCellMarked(result)) |
| return HashTraits<MappedType>::emptyValue(); |
| return result; |
| } |
| |
| template<typename KeyType, typename MappedType> |
| pair<typename HashMap<KeyType, MappedType>::iterator, bool> WeakGCMap<KeyType, MappedType>::set(const KeyType& key, const MappedType& value) |
| { |
| Heap::markCell(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::isCellMarked(result.first->second); |
| result.first->second = value; |
| } |
| return result; |
| } |
| |
| template<typename KeyType, typename MappedType> |
| bool WeakGCMap<KeyType, MappedType>::uncheckedRemove(const KeyType& key, const MappedType& value) |
| { |
| iterator it = m_map.find(key); |
| if (it == m_map.end()) |
| return false; |
| if (it->second != value) |
| return false; |
| m_map.remove(it); |
| return true; |
| } |
| |
| } // namespace JSC |
| |
| #endif // WeakGCMap_h |