Imported WebKit commit 2ea9d364d0f6efa8fa64acf19f451504c59be0e4 (http://svn.webkit.org/repository/webkit/trunk@104285)

1 files changed, 172 insertions, 0 deletions

diff --git a/Source/JavaScriptCore/runtime/StructureTransitionTable.h b/Source/JavaScriptCore/runtime/StructureTransitionTable.h
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+++ b/Source/JavaScriptCore/runtime/StructureTransitionTable.h
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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 "WeakGCMap.h"
+#include <wtf/HashFunctions.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 const int minimumTableSize = FirstTraits::minimumTableSize;
+
+        static void constructDeletedValue(TraitType& slot) { FirstTraits::constructDeletedValue(slot.first); }
+        static bool isDeletedValue(const TraitType& value) { return FirstTraits::isDeletedValue(value.first); }
+    };
+
+    struct WeakGCMapFinalizerCallback {
+        static void* finalizerContextFor(Hash::Key)
+        {
+            return 0;
+        }
+
+        static inline Hash::Key keyForFinalizer(void* context, Structure* structure)
+        {
+            return keyForWeakGCMapFinalizer(context, structure);
+        }
+    };
+
+    typedef WeakGCMap<Hash::Key, Structure, WeakGCMapFinalizerCallback, Hash, HashTraits> TransitionMap;
+
+    static Hash::Key keyForWeakGCMapFinalizer(void* context, Structure*);
+
+public:
+    StructureTransitionTable()
+        : m_data(UsingSingleSlotFlag)
+    {
+    }
+
+    ~StructureTransitionTable()
+    {
+        if (!isUsingSingleSlot()) {
+            delete map();
+            return;
+        }
+
+        HandleSlot slot = this->slot();
+        if (!slot)
+            return;
+        HandleHeap::heapFor(slot)->deallocate(slot);
+    }
+
+    inline void add(JSGlobalData&, 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);
+    }
+
+    HandleSlot slot() const
+    {
+        ASSERT(isUsingSingleSlot());
+        return reinterpret_cast<HandleSlot>(m_data & ~UsingSingleSlotFlag);
+    }
+
+    void setMap(TransitionMap* map)
+    {
+        ASSERT(isUsingSingleSlot());
+        
+        if (HandleSlot slot = this->slot())
+            HandleHeap::heapFor(slot)->deallocate(slot);
+
+        // 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());
+        if (HandleSlot slot = this->slot()) {
+            if (*slot)
+                return reinterpret_cast<Structure*>(slot->asCell());
+        }
+        return 0;
+    }
+    
+    void setSingleTransition(JSGlobalData& globalData, Structure* structure)
+    {
+        ASSERT(isUsingSingleSlot());
+        HandleSlot slot = this->slot();
+        if (!slot) {
+            slot = globalData.heap.handleHeap()->allocate();
+            HandleHeap::heapFor(slot)->makeWeak(slot, 0, 0);
+            m_data = reinterpret_cast<intptr_t>(slot) | UsingSingleSlotFlag;
+        }
+        HandleHeap::heapFor(slot)->writeBarrier(slot, reinterpret_cast<JSCell*>(structure));
+        *slot = reinterpret_cast<JSCell*>(structure);
+    }
+
+    intptr_t m_data;
+};
+
+} // namespace JSC
+
+#endif // StructureTransitionTable_h