JavaScriptCore-7600.1.4.11.8.tar.gz

[apple/javascriptcore.git] / runtime / JSString.h

diff --git a/runtime/JSString.h b/runtime/JSString.h
index 668064f854a8030ad383ddc66d11d0c92d732317..1287b66bee4a9ef4f89b122b6d7c7b37f294af7a 100644 (file)
--- a/runtime/JSString.h
+++ b/runtime/JSString.h
@@ -1,7 +1,7 @@
 /*
  *  Copyright (C) 1999-2001 Harri Porten (porten@kde.org)
  *  Copyright (C) 2001 Peter Kelly (pmk@post.com)
 /*
  *  Copyright (C) 1999-2001 Harri Porten (porten@kde.org)
  *  Copyright (C) 2001 Peter Kelly (pmk@post.com)

- *  Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
+ *  Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2014 Apple Inc. All rights reserved.

  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public


@@ -28,467 +28,425 @@
 #include "Identifier.h"
 #include "PropertyDescriptor.h"
 #include "PropertySlot.h"
 #include "Identifier.h"
 #include "PropertyDescriptor.h"
 #include "PropertySlot.h"

-#include "RopeImpl.h"

 #include "Structure.h"
 #include "Structure.h"

+#include <array>

 
 namespace JSC {
 
     class JSString;
 
 namespace JSC {
 
     class JSString;

+    class JSRopeString;
+    class LLIntOffsetsExtractor;

 
 

-    JSString* jsEmptyString(JSGlobalData*);
+    JSString* jsEmptyString(VM*);

     JSString* jsEmptyString(ExecState*);
     JSString* jsEmptyString(ExecState*);

-    JSString* jsString(JSGlobalData*, const UString&); // returns empty string if passed null string
-    JSString* jsString(ExecState*, const UString&); // returns empty string if passed null string
+    JSString* jsString(VM*, const String&); // returns empty string if passed null string
+    JSString* jsString(ExecState*, const String&); // returns empty string if passed null string

 
 

-    JSString* jsSingleCharacterString(JSGlobalData*, UChar);
+    JSString* jsSingleCharacterString(VM*, UChar);

     JSString* jsSingleCharacterString(ExecState*, UChar);
     JSString* jsSingleCharacterString(ExecState*, UChar);

-    JSString* jsSingleCharacterSubstring(ExecState*, const UString&, unsigned offset);
-    JSString* jsSubstring(JSGlobalData*, const UString&, unsigned offset, unsigned length);
-    JSString* jsSubstring(ExecState*, const UString&, unsigned offset, unsigned length);
+    JSString* jsSingleCharacterSubstring(ExecState*, const String&, unsigned offset);
+    JSString* jsSubstring(VM*, const String&, unsigned offset, unsigned length);
+    JSString* jsSubstring(ExecState*, const String&, unsigned offset, unsigned length);

 
     // Non-trivial strings are two or more characters long.
     // These functions are faster than just calling jsString.
 
     // Non-trivial strings are two or more characters long.
     // These functions are faster than just calling jsString.

-    JSString* jsNontrivialString(JSGlobalData*, const UString&);
-    JSString* jsNontrivialString(ExecState*, const UString&);
-    JSString* jsNontrivialString(JSGlobalData*, const char*);
-    JSString* jsNontrivialString(ExecState*, const char*);
+    JSString* jsNontrivialString(VM*, const String&);
+    JSString* jsNontrivialString(ExecState*, const String&);

 
     // Should be used for strings that are owned by an object that will
     // likely outlive the JSValue this makes, such as the parse tree or a
 
     // Should be used for strings that are owned by an object that will
     // likely outlive the JSValue this makes, such as the parse tree or a

-    // DOM object that contains a UString
-    JSString* jsOwnedString(JSGlobalData*, const UString&); 
-    JSString* jsOwnedString(ExecState*, const UString&); 
+    // DOM object that contains a String
+    JSString* jsOwnedString(VM*, const String&);
+    JSString* jsOwnedString(ExecState*, const String&);

 
 

-    class JS_EXPORTCLASS JSString : public JSCell {
+    JSRopeString* jsStringBuilder(VM*);
+
+    class JSString : public JSCell {

     public:
         friend class JIT;
     public:
         friend class JIT;

-        friend class JSGlobalData;
+        friend class VM;

         friend class SpecializedThunkJIT;
         friend class SpecializedThunkJIT;

+        friend class JSRopeString;
+        friend class MarkStack;
+        friend class SlotVisitor;

         friend struct ThunkHelpers;
 
         friend struct ThunkHelpers;
 

-        class RopeBuilder {
-        public:
-            RopeBuilder(unsigned fiberCount)
-                : m_index(0)
-                , m_rope(RopeImpl::tryCreateUninitialized(fiberCount))
-            {
-            }
-
-            bool isOutOfMemory() { return !m_rope; }
-
-            void append(RopeImpl::Fiber& fiber)
-            {
-                ASSERT(m_rope);
-                m_rope->initializeFiber(m_index, fiber);
-            }
-            void append(const UString& string)
-            {
-                ASSERT(m_rope);
-                m_rope->initializeFiber(m_index, string.impl());
-            }
-            void append(JSString* jsString)
-            {
-                if (jsString->isRope()) {
-                    for (unsigned i = 0; i < jsString->m_fiberCount; ++i)
-                        append(jsString->m_fibers[i]);
-                } else
-                    append(jsString->string());
-            }
-
-            PassRefPtr<RopeImpl> release()
-            {
-                ASSERT(m_index == m_rope->fiberCount());
-                return m_rope.release();
-            }
-
-            unsigned length() { return m_rope->length(); }
-
-        private:
-            unsigned m_index;
-            RefPtr<RopeImpl> m_rope;
-        };
-
-        class RopeIterator {
-            public:
-                RopeIterator() { }
+        typedef JSCell Base;

 
 

-                RopeIterator(RopeImpl::Fiber* fibers, size_t fiberCount)
-                {
-                    ASSERT(fiberCount);
-                    m_workQueue.append(WorkItem(fibers, fiberCount));
-                    skipRopes();
-                }
-
-                RopeIterator& operator++()
-                {
-                    WorkItem& item = m_workQueue.last();
-                    ASSERT(!RopeImpl::isRope(item.fibers[item.i]));
-                    if (++item.i == item.fiberCount)
-                        m_workQueue.removeLast();
-                    skipRopes();
-                    return *this;
-                }
-
-                StringImpl* operator*()
-                {
-                    WorkItem& item = m_workQueue.last();
-                    RopeImpl::Fiber fiber = item.fibers[item.i];
-                    ASSERT(!RopeImpl::isRope(fiber));
-                    return static_cast<StringImpl*>(fiber);
-                }
-
-                bool operator!=(const RopeIterator& other) const
-                {
-                    return m_workQueue != other.m_workQueue;
-                }
-
-            private:
-                struct WorkItem {
-                    WorkItem(RopeImpl::Fiber* fibers, size_t fiberCount)
-                        : fibers(fibers)
-                        , fiberCount(fiberCount)
-                        , i(0)
-                    {
-                    }
-
-                    bool operator!=(const WorkItem& other) const
-                    {
-                        return fibers != other.fibers || fiberCount != other.fiberCount || i != other.i;
-                    }
-
-                    RopeImpl::Fiber* fibers;
-                    size_t fiberCount;
-                    size_t i;
-                };
-
-                void skipRopes()
-                {
-                    if (m_workQueue.isEmpty())
-                        return;
-
-                    while (1) {
-                        WorkItem& item = m_workQueue.last();
-                        RopeImpl::Fiber fiber = item.fibers[item.i];
-                        if (!RopeImpl::isRope(fiber))
-                            break;
-                        RopeImpl* rope = static_cast<RopeImpl*>(fiber);
-                        if (++item.i == item.fiberCount)
-                            m_workQueue.removeLast();
-                        m_workQueue.append(WorkItem(rope->fibers(), rope->fiberCount()));
-                    }
-                }
-
-                Vector<WorkItem, 16> m_workQueue;
-        };
+        static const bool needsDestruction = true;
+        static const bool hasImmortalStructure = true;
+        static void destroy(JSCell*);

 
 

-        ALWAYS_INLINE JSString(JSGlobalData* globalData, const UString& value)
-            : JSCell(*globalData, globalData->stringStructure.get())
-            , m_length(value.length())
+    private:
+        JSString(VM& vm, PassRefPtr<StringImpl> value)
+            : JSCell(vm, vm.stringStructure.get())
+            , m_flags(0)

             , m_value(value)
             , m_value(value)

-            , m_fiberCount(0)

         {
         {

-            ASSERT(!m_value.isNull());
-            Heap::heap(this)->reportExtraMemoryCost(value.impl()->cost());

         }
 
         }
 

-        enum HasOtherOwnerType { HasOtherOwner };
-        JSString(JSGlobalData* globalData, const UString& value, HasOtherOwnerType)
-            : JSCell(*globalData, globalData->stringStructure.get())
-            , m_length(value.length())
-            , m_value(value)
-            , m_fiberCount(0)
+        JSString(VM& vm)
+            : JSCell(vm, vm.stringStructure.get())
+            , m_flags(0)

         {
         {

-            ASSERT(!m_value.isNull());

         }
         }

-        JSString(JSGlobalData* globalData, PassRefPtr<StringImpl> value, HasOtherOwnerType)
-            : JSCell(*globalData, globalData->stringStructure.get())
-            , m_length(value->length())
-            , m_value(value)
-            , m_fiberCount(0)
+
+        void finishCreation(VM& vm, size_t length)

         {
             ASSERT(!m_value.isNull());
         {
             ASSERT(!m_value.isNull());

+            Base::finishCreation(vm);
+            m_length = length;
+            setIs8Bit(m_value.impl()->is8Bit());
+            vm.m_newStringsSinceLastHashCons++;

         }
         }

-        JSString(JSGlobalData* globalData, PassRefPtr<RopeImpl> rope)
-            : JSCell(*globalData, globalData->stringStructure.get())
-            , m_length(rope->length())
-            , m_fiberCount(1)
-        {
-            m_fibers[0] = rope.leakRef();
-        }
-        // This constructor constructs a new string by concatenating s1 & s2.
-        // This should only be called with fiberCount <= 3.
-        JSString(JSGlobalData* globalData, unsigned fiberCount, JSString* s1, JSString* s2)
-            : JSCell(*globalData, globalData->stringStructure.get())
-            , m_length(s1->length() + s2->length())
-            , m_fiberCount(fiberCount)
+
+        void finishCreation(VM& vm, size_t length, size_t cost)

         {
         {

-            ASSERT(fiberCount <= s_maxInternalRopeLength);
-            unsigned index = 0;
-            appendStringInConstruct(index, s1);
-            appendStringInConstruct(index, s2);
-            ASSERT(fiberCount == index);
+            ASSERT(!m_value.isNull());
+            Base::finishCreation(vm);
+            m_length = length;
+            setIs8Bit(m_value.impl()->is8Bit());
+            Heap::heap(this)->reportExtraMemoryCost(cost);
+            vm.m_newStringsSinceLastHashCons++;

         }
         }

-        // This constructor constructs a new string by concatenating s1 & s2.
-        // This should only be called with fiberCount <= 3.
-        JSString(JSGlobalData* globalData, unsigned fiberCount, JSString* s1, const UString& u2)
-            : JSCell(*globalData, globalData->stringStructure.get())
-            , m_length(s1->length() + u2.length())
-            , m_fiberCount(fiberCount)
+
+    protected:
+        void finishCreation(VM& vm)

         {
         {

-            ASSERT(fiberCount <= s_maxInternalRopeLength);
-            unsigned index = 0;
-            appendStringInConstruct(index, s1);
-            appendStringInConstruct(index, u2);
-            ASSERT(fiberCount == index);
+            Base::finishCreation(vm);
+            m_length = 0;
+            setIs8Bit(true);
+            vm.m_newStringsSinceLastHashCons++;

         }
         }

-        // This constructor constructs a new string by concatenating s1 & s2.
-        // This should only be called with fiberCount <= 3.
-        JSString(JSGlobalData* globalData, unsigned fiberCount, const UString& u1, JSString* s2)
-            : JSCell(*globalData, globalData->stringStructure.get())
-            , m_length(u1.length() + s2->length())
-            , m_fiberCount(fiberCount)
+            
+    public:
+        static JSString* create(VM& vm, PassRefPtr<StringImpl> value)

         {
         {

-            ASSERT(fiberCount <= s_maxInternalRopeLength);
-            unsigned index = 0;
-            appendStringInConstruct(index, u1);
-            appendStringInConstruct(index, s2);
-            ASSERT(fiberCount == index);
+            ASSERT(value);
+            int32_t length = value->length();
+            RELEASE_ASSERT(length >= 0);
+            size_t cost = value->cost();
+            JSString* newString = new (NotNull, allocateCell<JSString>(vm.heap)) JSString(vm, value);
+            newString->finishCreation(vm, length, cost);
+            return newString;

         }
         }

-        // This constructor constructs a new string by concatenating v1, v2 & v3.
-        // This should only be called with fiberCount <= 3 ... which since every
-        // value must require a fiberCount of at least one implies that the length
-        // for each value must be exactly 1!
-        JSString(ExecState* exec, JSValue v1, JSValue v2, JSValue v3)
-            : JSCell(exec->globalData(), exec->globalData().stringStructure.get())
-            , m_length(0)
-            , m_fiberCount(s_maxInternalRopeLength)
+        static JSString* createHasOtherOwner(VM& vm, PassRefPtr<StringImpl> value)

         {
         {

-            unsigned index = 0;
-            appendValueInConstructAndIncrementLength(exec, index, v1);
-            appendValueInConstructAndIncrementLength(exec, index, v2);
-            appendValueInConstructAndIncrementLength(exec, index, v3);
-            ASSERT(index == s_maxInternalRopeLength);
+            ASSERT(value);
+            size_t length = value->length();
+            JSString* newString = new (NotNull, allocateCell<JSString>(vm.heap)) JSString(vm, value);
+            newString->finishCreation(vm, length);
+            return newString;

         }
 
         }
 

-        // This constructor constructs a new string by concatenating u1 & u2.
-        JSString(JSGlobalData* globalData, const UString& u1, const UString& u2)
-            : JSCell(*globalData, globalData->stringStructure.get())
-            , m_length(u1.length() + u2.length())
-            , m_fiberCount(2)
+        Identifier toIdentifier(ExecState*) const;
+        AtomicString toAtomicString(ExecState*) const;
+        AtomicStringImpl* toExistingAtomicString(ExecState*) const;
+        const String& value(ExecState*) const;
+        const String& tryGetValue() const;
+        const StringImpl* tryGetValueImpl() const;
+        unsigned length() const { return m_length; }
+
+        JSValue toPrimitive(ExecState*, PreferredPrimitiveType) const;
+        JS_EXPORT_PRIVATE bool toBoolean() const;
+        bool getPrimitiveNumber(ExecState*, double& number, JSValue&) const;
+        JSObject* toObject(ExecState*, JSGlobalObject*) const;
+        double toNumber(ExecState*) const;
+            
+        bool getStringPropertySlot(ExecState*, PropertyName, PropertySlot&);
+        bool getStringPropertySlot(ExecState*, unsigned propertyName, PropertySlot&);
+        bool getStringPropertyDescriptor(ExecState*, PropertyName, PropertyDescriptor&);
+
+        bool canGetIndex(unsigned i) { return i < m_length; }
+        JSString* getIndex(ExecState*, unsigned);
+
+        static Structure* createStructure(VM& vm, JSGlobalObject* globalObject, JSValue proto)

         {
         {

-            unsigned index = 0;
-            appendStringInConstruct(index, u1);
-            appendStringInConstruct(index, u2);
-            ASSERT(index <= s_maxInternalRopeLength);
+            return Structure::create(vm, globalObject, proto, TypeInfo(StringType, StructureFlags), info());

         }
 
         }
 

-        // This constructor constructs a new string by concatenating u1, u2 & u3.
-        JSString(JSGlobalData* globalData, const UString& u1, const UString& u2, const UString& u3)
-            : JSCell(*globalData, globalData->stringStructure.get())
-            , m_length(u1.length() + u2.length() + u3.length())
-            , m_fiberCount(s_maxInternalRopeLength)
+        static size_t offsetOfLength() { return OBJECT_OFFSETOF(JSString, m_length); }
+        static size_t offsetOfFlags() { return OBJECT_OFFSETOF(JSString, m_flags); }
+        static size_t offsetOfValue() { return OBJECT_OFFSETOF(JSString, m_value); }
+
+        DECLARE_EXPORT_INFO;
+
+        static void dumpToStream(const JSCell*, PrintStream&);
+        static void visitChildren(JSCell*, SlotVisitor&);
+
+        enum {
+            HashConsLock = 1u << 2,
+            IsHashConsSingleton = 1u << 1,
+            Is8Bit = 1u
+        };
+
+    protected:
+        static const unsigned StructureFlags = OverridesGetOwnPropertySlot | InterceptsGetOwnPropertySlotByIndexEvenWhenLengthIsNotZero | StructureIsImmortal;
+
+        friend class JSValue;
+            
+        bool isRope() const { return m_value.isNull(); }
+        bool is8Bit() const { return m_flags & Is8Bit; }
+        void setIs8Bit(bool flag)

         {
         {

-            unsigned index = 0;
-            appendStringInConstruct(index, u1);
-            appendStringInConstruct(index, u2);
-            appendStringInConstruct(index, u3);
-            ASSERT(index <= s_maxInternalRopeLength);
+            if (flag)
+                m_flags |= Is8Bit;
+            else
+                m_flags &= ~Is8Bit;

         }
         }

+        bool shouldTryHashCons();
+        bool isHashConsSingleton() const { return m_flags & IsHashConsSingleton; }
+        void clearHashConsSingleton() { m_flags &= ~IsHashConsSingleton; }
+        void setHashConsSingleton() { m_flags |= IsHashConsSingleton; }
+        bool tryHashConsLock();
+        void releaseHashConsLock();
+
+        unsigned m_flags;
+            
+        // A string is represented either by a String or a rope of fibers.
+        unsigned m_length;
+        mutable String m_value;
+
+    private:
+        friend class LLIntOffsetsExtractor;
+            
+        static JSValue toThis(JSCell*, ExecState*, ECMAMode);
+
+        String& string() { ASSERT(!isRope()); return m_value; }
+
+        friend JSValue jsString(ExecState*, JSString*, JSString*);
+        friend JSString* jsSubstring(ExecState*, JSString*, unsigned offset, unsigned length);
+    };
+
+    class JSRopeString : public JSString {
+        friend class JSString;
+
+        friend JSRopeString* jsStringBuilder(VM*);

 
 

-        ~JSString()
+        class RopeBuilder {
+        public:
+            RopeBuilder(VM& vm)
+                : m_vm(vm)
+                , m_jsString(jsStringBuilder(&vm))
+                , m_index(0)
+            {
+            }
+
+            bool append(JSString* jsString)
+            {
+                if (m_index == JSRopeString::s_maxInternalRopeLength)
+                    expand();
+                if (static_cast<int32_t>(m_jsString->length() + jsString->length()) < 0) {
+                    m_jsString = nullptr;
+                    return false;
+                }
+                m_jsString->append(m_vm, m_index++, jsString);
+                return true;
+            }
+
+            JSRopeString* release()
+            {
+                RELEASE_ASSERT(m_jsString);
+                JSRopeString* tmp = m_jsString;
+                m_jsString = 0;
+                return tmp;
+            }
+
+            unsigned length() const { return m_jsString->m_length; }
+
+        private:
+            void expand();
+                
+            VM& m_vm;
+            JSRopeString* m_jsString;
+            size_t m_index;
+        };
+            
+    private:
+        JSRopeString(VM& vm)
+            : JSString(vm)

         {
         {

-            ASSERT(vptr() == JSGlobalData::jsStringVPtr);
-            for (unsigned i = 0; i < m_fiberCount; ++i)
-                RopeImpl::deref(m_fibers[i]);

         }
 
         }
 

-        const UString& value(ExecState* exec) const
+        void finishCreation(VM& vm, JSString* s1, JSString* s2)

         {
         {

-            if (isRope())
-                resolveRope(exec);
-            return m_value;
+            Base::finishCreation(vm);
+            m_length = s1->length() + s2->length();
+            setIs8Bit(s1->is8Bit() && s2->is8Bit());
+            m_fibers[0].set(vm, this, s1);
+            m_fibers[1].set(vm, this, s2);

         }
         }

-        const UString& tryGetValue() const
+            
+        void finishCreation(VM& vm, JSString* s1, JSString* s2, JSString* s3)

         {
         {

-            if (isRope())
-                resolveRope(0);
-            return m_value;
+            Base::finishCreation(vm);
+            m_length = s1->length() + s2->length() + s3->length();
+            setIs8Bit(s1->is8Bit() && s2->is8Bit() &&  s3->is8Bit());
+            m_fibers[0].set(vm, this, s1);
+            m_fibers[1].set(vm, this, s2);
+            m_fibers[2].set(vm, this, s3);

         }
         }

-        unsigned length() { return m_length; }
-
-        bool getStringPropertySlot(ExecState*, const Identifier& propertyName, PropertySlot&);
-        bool getStringPropertySlot(ExecState*, unsigned propertyName, PropertySlot&);
-        bool getStringPropertyDescriptor(ExecState*, const Identifier& propertyName, PropertyDescriptor&);
-
-        bool canGetIndex(unsigned i) { return i < m_length; }
-        JSString* getIndex(ExecState*, unsigned);
-        JSString* getIndexSlowCase(ExecState*, unsigned);
-
-        JSValue replaceCharacter(ExecState*, UChar, const UString& replacement);

 
 

-        static Structure* createStructure(JSGlobalData& globalData, JSValue proto)
+        void finishCreation(VM& vm)

         {
         {

-            return Structure::create(globalData, proto, TypeInfo(StringType, OverridesGetOwnPropertySlot | NeedsThisConversion), AnonymousSlotCount, &s_info);
+            JSString::finishCreation(vm);

         }
         }

-        
-        static const ClassInfo s_info;

 
 

-    private:
-        JSString(VPtrStealingHackType) 
-            : JSCell(VPtrStealingHack)
-            , m_fiberCount(0)
+        void append(VM& vm, size_t index, JSString* jsString)

         {
         {

+            m_fibers[index].set(vm, this, jsString);
+            m_length += jsString->m_length;
+            RELEASE_ASSERT(static_cast<int32_t>(m_length) >= 0);
+            setIs8Bit(is8Bit() && jsString->is8Bit());

         }
 
         }
 

-        void resolveRope(ExecState*) const;
-        void resolveRopeSlowCase(ExecState*, UChar*) const;
-        void outOfMemory(ExecState*) const;
-        JSString* substringFromRope(ExecState*, unsigned offset, unsigned length);
-
-        void appendStringInConstruct(unsigned& index, const UString& string)
+        static JSRopeString* createNull(VM& vm)

         {
         {

-            StringImpl* impl = string.impl();
-            impl->ref();
-            m_fibers[index++] = impl;
+            JSRopeString* newString = new (NotNull, allocateCell<JSRopeString>(vm.heap)) JSRopeString(vm);
+            newString->finishCreation(vm);
+            return newString;

         }
 
         }
 

-        void appendStringInConstruct(unsigned& index, JSString* jsString)
+    public:
+        static JSString* create(VM& vm, JSString* s1, JSString* s2)

         {
         {

-            if (jsString->isRope()) {
-                for (unsigned i = 0; i < jsString->m_fiberCount; ++i) {
-                    RopeImpl::Fiber fiber = jsString->m_fibers[i];
-                    fiber->ref();
-                    m_fibers[index++] = fiber;
-                }
-            } else
-                appendStringInConstruct(index, jsString->string());
+            JSRopeString* newString = new (NotNull, allocateCell<JSRopeString>(vm.heap)) JSRopeString(vm);
+            newString->finishCreation(vm, s1, s2);
+            return newString;

         }
         }

-
-        void appendValueInConstructAndIncrementLength(ExecState* exec, unsigned& index, JSValue v)
+        static JSString* create(VM& vm, JSString* s1, JSString* s2, JSString* s3)

         {
         {

-            if (v.isString()) {
-                ASSERT(v.asCell()->isString());
-                JSString* s = static_cast<JSString*>(v.asCell());
-                ASSERT(s->fiberCount() == 1);
-                appendStringInConstruct(index, s);
-                m_length += s->length();
-            } else {
-                UString u(v.toString(exec));
-                StringImpl* impl = u.impl();
-                impl->ref();
-                m_fibers[index++] = impl;
-                m_length += u.length();
-            }
+            JSRopeString* newString = new (NotNull, allocateCell<JSRopeString>(vm.heap)) JSRopeString(vm);
+            newString->finishCreation(vm, s1, s2, s3);
+            return newString;

         }
 
         }
 

-        virtual JSValue toPrimitive(ExecState*, PreferredPrimitiveType) const;
-        virtual bool getPrimitiveNumber(ExecState*, double& number, JSValue& value);
-        virtual bool toBoolean(ExecState*) const;
-        virtual double toNumber(ExecState*) const;
-        virtual JSObject* toObject(ExecState*, JSGlobalObject*) const;
-        virtual UString toString(ExecState*) const;
-
-        virtual JSObject* toThisObject(ExecState*) const;
-
-        // Actually getPropertySlot, not getOwnPropertySlot (see JSCell).
-        virtual bool getOwnPropertySlot(ExecState*, const Identifier& propertyName, PropertySlot&);
-        virtual bool getOwnPropertySlot(ExecState*, unsigned propertyName, PropertySlot&);
-        virtual bool getOwnPropertyDescriptor(ExecState*, const Identifier&, PropertyDescriptor&);
+        void visitFibers(SlotVisitor&);
+            
+        static ptrdiff_t offsetOfFibers() { return OBJECT_OFFSETOF(JSRopeString, m_fibers); }

 
         static const unsigned s_maxInternalRopeLength = 3;
 
         static const unsigned s_maxInternalRopeLength = 3;

+            
+    private:
+        friend JSValue jsStringFromRegisterArray(ExecState*, Register*, unsigned);
+        friend JSValue jsStringFromArguments(ExecState*, JSValue);
+
+        JS_EXPORT_PRIVATE void resolveRope(ExecState*) const;
+        JS_EXPORT_PRIVATE void resolveRopeToAtomicString(ExecState*) const;
+        JS_EXPORT_PRIVATE AtomicStringImpl* resolveRopeToExistingAtomicString(ExecState*) const;
+        void resolveRopeSlowCase8(LChar*) const;
+        void resolveRopeSlowCase(UChar*) const;
+        void outOfMemory(ExecState*) const;
+        void resolveRopeInternal8(LChar*) const;
+        void resolveRopeInternal16(UChar*) const;
+        void clearFibers() const;
+            
+        JS_EXPORT_PRIVATE JSString* getIndexSlowCase(ExecState*, unsigned);

 
 

-        // A string is represented either by a UString or a RopeImpl.
-        unsigned m_length;
-        mutable UString m_value;
-        mutable unsigned m_fiberCount;
-        mutable FixedArray<RopeImpl::Fiber, s_maxInternalRopeLength> m_fibers;
-
-        bool isRope() const { return m_fiberCount; }
-        UString& string() { ASSERT(!isRope()); return m_value; }
-        unsigned fiberCount() { return m_fiberCount ? m_fiberCount : 1; }
-
-        friend JSValue jsString(ExecState* exec, JSString* s1, JSString* s2);
-        friend JSValue jsString(ExecState* exec, const UString& u1, JSString* s2);
-        friend JSValue jsString(ExecState* exec, JSString* s1, const UString& u2);
-        friend JSValue jsString(ExecState* exec, Register* strings, unsigned count);
-        friend JSValue jsString(ExecState* exec, JSValue thisValue);
-        friend JSString* jsSubstring(ExecState* exec, JSString* s, unsigned offset, unsigned length);
+        mutable std::array<WriteBarrier<JSString>, s_maxInternalRopeLength> m_fibers;

     };
 
     };
 

-    JSString* asString(JSValue);

 
 

-    // When an object is created from a different DLL, MSVC changes vptr to a "local" one right after invoking a constructor,
-    // see <http://groups.google.com/group/microsoft.public.vc.language/msg/55cdcefeaf770212>.
-    // This breaks isJSString(), and we don't need that hack anyway, so we change vptr back to primary one.
-    // The below function must be called by any inline function that invokes a JSString constructor.
-#if COMPILER(MSVC) && !defined(BUILDING_JavaScriptCore)
-    inline JSString* fixupVPtr(JSGlobalData* globalData, JSString* string) { string->setVPtr(globalData->jsStringVPtr); return string; }
-#else
-    inline JSString* fixupVPtr(JSGlobalData*, JSString* string) { return string; }
-#endif
+    inline const StringImpl* JSString::tryGetValueImpl() const
+    {
+        return m_value.impl();
+    }
+
+    JSString* asString(JSValue);

 
     inline JSString* asString(JSValue value)
     {
         ASSERT(value.asCell()->isString());
 
     inline JSString* asString(JSValue value)
     {
         ASSERT(value.asCell()->isString());

-        return static_cast<JSString*>(value.asCell());
+        return jsCast<JSString*>(value.asCell());

     }
 
     }
 

-    inline JSString* jsEmptyString(JSGlobalData* globalData)
+    inline JSString* jsEmptyString(VM* vm)

     {
     {

-        return globalData->smallStrings.emptyString(globalData);
+        return vm->smallStrings.emptyString();

     }
 
     }
 

-    inline JSString* jsSingleCharacterString(JSGlobalData* globalData, UChar c)
+    ALWAYS_INLINE JSString* jsSingleCharacterString(VM* vm, UChar c)

     {
         if (c <= maxSingleCharacterString)
     {
         if (c <= maxSingleCharacterString)

-            return globalData->smallStrings.singleCharacterString(globalData, c);
-        return fixupVPtr(globalData, new (globalData) JSString(globalData, UString(&c, 1)));
+            return vm->smallStrings.singleCharacterString(c);
+        return JSString::create(*vm, String(&c, 1).impl());

     }
 
     }
 

-    inline JSString* jsSingleCharacterSubstring(ExecState* exec, const UString& s, unsigned offset)
+    ALWAYS_INLINE JSString* jsSingleCharacterSubstring(ExecState* exec, const String& s, unsigned offset)

     {
     {

-        JSGlobalData* globalData = &exec->globalData();
+        VM* vm = &exec->vm();

         ASSERT(offset < static_cast<unsigned>(s.length()));
         ASSERT(offset < static_cast<unsigned>(s.length()));

-        UChar c = s.characters()[offset];
+        UChar c = s.characterAt(offset);

         if (c <= maxSingleCharacterString)
         if (c <= maxSingleCharacterString)

-            return globalData->smallStrings.singleCharacterString(globalData, c);
-        return fixupVPtr(globalData, new (globalData) JSString(globalData, UString(StringImpl::create(s.impl(), offset, 1))));
+            return vm->smallStrings.singleCharacterString(c);
+        return JSString::create(*vm, StringImpl::createSubstringSharingImpl(s.impl(), offset, 1));
+    }
+
+    inline JSString* jsNontrivialString(VM* vm, const String& s)
+    {
+        ASSERT(s.length() > 1);
+        return JSString::create(*vm, s.impl());

     }
 
     }
 

-    inline JSString* jsNontrivialString(JSGlobalData* globalData, const char* s)
+    ALWAYS_INLINE Identifier JSString::toIdentifier(ExecState* exec) const

     {
     {

-        ASSERT(s);
-        ASSERT(s[0]);
-        ASSERT(s[1]);
-        return fixupVPtr(globalData, new (globalData) JSString(globalData, s));
+        return Identifier(exec, toAtomicString(exec));

     }
 
     }
 

-    inline JSString* jsNontrivialString(JSGlobalData* globalData, const UString& s)
+    ALWAYS_INLINE AtomicString JSString::toAtomicString(ExecState* exec) const

     {
     {

-        ASSERT(s.length() > 1);
-        return fixupVPtr(globalData, new (globalData) JSString(globalData, s));
+        if (isRope())
+            static_cast<const JSRopeString*>(this)->resolveRopeToAtomicString(exec);
+        return AtomicString(m_value);
+    }
+
+    ALWAYS_INLINE AtomicStringImpl* JSString::toExistingAtomicString(ExecState* exec) const
+    {
+        if (isRope())
+            return static_cast<const JSRopeString*>(this)->resolveRopeToExistingAtomicString(exec);
+        if (m_value.impl()->isAtomic())
+            return static_cast<AtomicStringImpl*>(m_value.impl());
+        if (AtomicStringImpl* existingAtomicString = AtomicString::find(m_value.impl())) {
+            m_value = *existingAtomicString;
+            return existingAtomicString;
+        }
+        return nullptr;
+    }
+
+    inline const String& JSString::value(ExecState* exec) const
+    {
+        if (isRope())
+            static_cast<const JSRopeString*>(this)->resolveRope(exec);
+        return m_value;
+    }
+
+    inline const String& JSString::tryGetValue() const
+    {
+        if (isRope())
+            static_cast<const JSRopeString*>(this)->resolveRope(0);
+        return m_value;

     }
 
     inline JSString* JSString::getIndex(ExecState* exec, unsigned i)
     {
         ASSERT(canGetIndex(i));
         if (isRope())
     }
 
     inline JSString* JSString::getIndex(ExecState* exec, unsigned i)
     {
         ASSERT(canGetIndex(i));
         if (isRope())

-            return getIndexSlowCase(exec, i);
+            return static_cast<JSRopeString*>(this)->getIndexSlowCase(exec, i);

         ASSERT(i < m_value.length());
         return jsSingleCharacterSubstring(exec, m_value, i);
     }
 
         ASSERT(i < m_value.length());
         return jsSingleCharacterSubstring(exec, m_value, i);
     }
 

-    inline JSString* jsString(JSGlobalData* globalData, const UString& s)
+    inline JSString* jsString(VM* vm, const String& s)

     {
         int size = s.length();
         if (!size)
     {
         int size = s.length();
         if (!size)

-            return globalData->smallStrings.emptyString(globalData);
+            return vm->smallStrings.emptyString();

         if (size == 1) {
         if (size == 1) {

-            UChar c = s.characters()[0];
+            UChar c = s.characterAt(0);

             if (c <= maxSingleCharacterString)
             if (c <= maxSingleCharacterString)

-                return globalData->smallStrings.singleCharacterString(globalData, c);
+                return vm->smallStrings.singleCharacterString(c);

         }
         }

-        return fixupVPtr(globalData, new (globalData) JSString(globalData, s));
+        return JSString::create(*vm, s.impl());

     }
 
     inline JSString* jsSubstring(ExecState* exec, JSString* s, unsigned offset, unsigned length)
     }
 
     inline JSString* jsSubstring(ExecState* exec, JSString* s, unsigned offset, unsigned length)


@@ -496,118 +454,176 @@ namespace JSC {
         ASSERT(offset <= static_cast<unsigned>(s->length()));
         ASSERT(length <= static_cast<unsigned>(s->length()));
         ASSERT(offset + length <= static_cast<unsigned>(s->length()));
         ASSERT(offset <= static_cast<unsigned>(s->length()));
         ASSERT(length <= static_cast<unsigned>(s->length()));
         ASSERT(offset + length <= static_cast<unsigned>(s->length()));

-        JSGlobalData* globalData = &exec->globalData();
+        VM* vm = &exec->vm();

         if (!length)
         if (!length)

-            return globalData->smallStrings.emptyString(globalData);
-        if (s->isRope())
-            return s->substringFromRope(exec, offset, length);
-        return jsSubstring(globalData, s->m_value, offset, length);
+            return vm->smallStrings.emptyString();
+        return jsSubstring(vm, s->value(exec), offset, length);

     }
 
     }
 

-    inline JSString* jsSubstring(JSGlobalData* globalData, const UString& s, unsigned offset, unsigned length)
+    inline JSString* jsSubstring8(VM* vm, const String& s, unsigned offset, unsigned length)

     {
         ASSERT(offset <= static_cast<unsigned>(s.length()));
         ASSERT(length <= static_cast<unsigned>(s.length()));
         ASSERT(offset + length <= static_cast<unsigned>(s.length()));
         if (!length)
     {
         ASSERT(offset <= static_cast<unsigned>(s.length()));
         ASSERT(length <= static_cast<unsigned>(s.length()));
         ASSERT(offset + length <= static_cast<unsigned>(s.length()));
         if (!length)

-            return globalData->smallStrings.emptyString(globalData);
+            return vm->smallStrings.emptyString();

         if (length == 1) {
         if (length == 1) {

-            UChar c = s.characters()[offset];
+            UChar c = s.characterAt(offset);

             if (c <= maxSingleCharacterString)
             if (c <= maxSingleCharacterString)

-                return globalData->smallStrings.singleCharacterString(globalData, c);
+                return vm->smallStrings.singleCharacterString(c);

         }
         }

-        return fixupVPtr(globalData, new (globalData) JSString(globalData, UString(StringImpl::create(s.impl(), offset, length)), JSString::HasOtherOwner));
+        return JSString::createHasOtherOwner(*vm, StringImpl::createSubstringSharingImpl8(s.impl(), offset, length));

     }
 
     }
 

-    inline JSString* jsOwnedString(JSGlobalData* globalData, const UString& s)
+    inline JSString* jsSubstring(VM* vm, const String& s, unsigned offset, unsigned length)
+    {
+        ASSERT(offset <= static_cast<unsigned>(s.length()));
+        ASSERT(length <= static_cast<unsigned>(s.length()));
+        ASSERT(offset + length <= static_cast<unsigned>(s.length()));
+        if (!length)
+            return vm->smallStrings.emptyString();
+        if (length == 1) {
+            UChar c = s.characterAt(offset);
+            if (c <= maxSingleCharacterString)
+                return vm->smallStrings.singleCharacterString(c);
+        }
+        return JSString::createHasOtherOwner(*vm, StringImpl::createSubstringSharingImpl(s.impl(), offset, length));
+    }
+
+    inline JSString* jsOwnedString(VM* vm, const String& s)

     {
         int size = s.length();
         if (!size)
     {
         int size = s.length();
         if (!size)

-            return globalData->smallStrings.emptyString(globalData);
+            return vm->smallStrings.emptyString();

         if (size == 1) {
         if (size == 1) {

-            UChar c = s.characters()[0];
+            UChar c = s.characterAt(0);

             if (c <= maxSingleCharacterString)
             if (c <= maxSingleCharacterString)

-                return globalData->smallStrings.singleCharacterString(globalData, c);
+                return vm->smallStrings.singleCharacterString(c);

         }
         }

-        return fixupVPtr(globalData, new (globalData) JSString(globalData, s, JSString::HasOtherOwner));
+        return JSString::createHasOtherOwner(*vm, s.impl());

     }
 
     }
 

-    inline JSString* jsEmptyString(ExecState* exec) { return jsEmptyString(&exec->globalData()); }
-    inline JSString* jsString(ExecState* exec, const UString& s) { return jsString(&exec->globalData(), s); }
-    inline JSString* jsSingleCharacterString(ExecState* exec, UChar c) { return jsSingleCharacterString(&exec->globalData(), c); }
-    inline JSString* jsSubstring(ExecState* exec, const UString& s, unsigned offset, unsigned length) { return jsSubstring(&exec->globalData(), s, offset, length); }
-    inline JSString* jsNontrivialString(ExecState* exec, const UString& s) { return jsNontrivialString(&exec->globalData(), s); }
-    inline JSString* jsNontrivialString(ExecState* exec, const char* s) { return jsNontrivialString(&exec->globalData(), s); }
-    inline JSString* jsOwnedString(ExecState* exec, const UString& s) { return jsOwnedString(&exec->globalData(), s); } 
+    inline JSRopeString* jsStringBuilder(VM* vm)
+    {
+        return JSRopeString::createNull(*vm);
+    }
+
+    inline JSString* jsEmptyString(ExecState* exec) { return jsEmptyString(&exec->vm()); }
+    inline JSString* jsString(ExecState* exec, const String& s) { return jsString(&exec->vm(), s); }
+    inline JSString* jsSingleCharacterString(ExecState* exec, UChar c) { return jsSingleCharacterString(&exec->vm(), c); }
+    inline JSString* jsSubstring8(ExecState* exec, const String& s, unsigned offset, unsigned length) { return jsSubstring8(&exec->vm(), s, offset, length); }
+    inline JSString* jsSubstring(ExecState* exec, const String& s, unsigned offset, unsigned length) { return jsSubstring(&exec->vm(), s, offset, length); }
+    inline JSString* jsNontrivialString(ExecState* exec, const String& s) { return jsNontrivialString(&exec->vm(), s); }
+    inline JSString* jsOwnedString(ExecState* exec, const String& s) { return jsOwnedString(&exec->vm(), s); }
+
+    JS_EXPORT_PRIVATE JSString* jsStringWithCacheSlowCase(VM&, StringImpl&);
+
+    ALWAYS_INLINE JSString* jsStringWithCache(ExecState* exec, const String& s)
+    {
+        VM& vm = exec->vm();
+        StringImpl* stringImpl = s.impl();
+        if (!stringImpl || !stringImpl->length())
+            return jsEmptyString(&vm);
+
+        if (stringImpl->length() == 1) {
+            UChar singleCharacter = (*stringImpl)[0u];
+            if (singleCharacter <= maxSingleCharacterString)
+                return vm.smallStrings.singleCharacterString(static_cast<unsigned char>(singleCharacter));
+        }
+
+        if (JSString* lastCachedString = vm.lastCachedString.get()) {
+            if (lastCachedString->tryGetValueImpl() == stringImpl)
+                return lastCachedString;
+        }
+
+        return jsStringWithCacheSlowCase(vm, *stringImpl);
+    }
+
+    ALWAYS_INLINE JSString* jsStringWithCache(ExecState* exec, const AtomicString& s)
+    {
+        return jsStringWithCache(exec, s.string());
+    }

 
 

-    ALWAYS_INLINE bool JSString::getStringPropertySlot(ExecState* exec, const Identifier& propertyName, PropertySlot& slot)
+    ALWAYS_INLINE bool JSString::getStringPropertySlot(ExecState* exec, PropertyName propertyName, PropertySlot& slot)

     {
         if (propertyName == exec->propertyNames().length) {
     {
         if (propertyName == exec->propertyNames().length) {

-            slot.setValue(jsNumber(m_length));
+            slot.setValue(this, DontEnum | DontDelete | ReadOnly, jsNumber(m_length));

             return true;
         }
 
             return true;
         }
 

-        bool isStrictUInt32;
-        unsigned i = propertyName.toUInt32(isStrictUInt32);
-        if (isStrictUInt32 && i < m_length) {
-            slot.setValue(getIndex(exec, i));
+        unsigned i = propertyName.asIndex();
+        if (i < m_length) {
+            ASSERT(i != PropertyName::NotAnIndex); // No need for an explicit check, the above test would always fail!
+            slot.setValue(this, DontDelete | ReadOnly, getIndex(exec, i));

             return true;
         }
 
         return false;
     }
             return true;
         }
 
         return false;
     }

-        
+            

     ALWAYS_INLINE bool JSString::getStringPropertySlot(ExecState* exec, unsigned propertyName, PropertySlot& slot)
     {
         if (propertyName < m_length) {
     ALWAYS_INLINE bool JSString::getStringPropertySlot(ExecState* exec, unsigned propertyName, PropertySlot& slot)
     {
         if (propertyName < m_length) {

-            slot.setValue(getIndex(exec, propertyName));
+            slot.setValue(this, DontDelete | ReadOnly, getIndex(exec, propertyName));

             return true;
         }
 
         return false;
     }
 
             return true;
         }
 
         return false;
     }
 

-    inline bool isJSString(JSGlobalData* globalData, JSValue v) { return v.isCell() && v.asCell()->vptr() == globalData->jsStringVPtr; }
+    inline bool isJSString(JSValue v) { return v.isCell() && v.asCell()->type() == StringType; }

 
     // --- JSValue inlines ----------------------------
 
     // --- JSValue inlines ----------------------------

+        
+    inline bool JSValue::toBoolean(ExecState* exec) const
+    {
+        if (isInt32())
+            return asInt32();
+        if (isDouble())
+            return asDouble() > 0.0 || asDouble() < 0.0; // false for NaN
+        if (isCell())
+            return asCell()->toBoolean(exec);
+        return isTrue(); // false, null, and undefined all convert to false.
+    }
+
+    inline JSString* JSValue::toString(ExecState* exec) const
+    {
+        if (isString())
+            return jsCast<JSString*>(asCell());
+        return toStringSlowCase(exec);
+    }

 
 

-    inline UString JSValue::toString(ExecState* exec) const
+    inline String JSValue::toWTFString(ExecState* exec) const

     {
         if (isString())
             return static_cast<JSString*>(asCell())->value(exec);
     {
         if (isString())
             return static_cast<JSString*>(asCell())->value(exec);

-        if (isInt32())
-            return exec->globalData().numericStrings.add(asInt32());
-        if (isDouble())
-            return exec->globalData().numericStrings.add(asDouble());
-        if (isTrue())
-            return "true";
-        if (isFalse())
-            return "false";
-        if (isNull())
-            return "null";
-        if (isUndefined())
-            return "undefined";
-        ASSERT(isCell());
-        return asCell()->toString(exec);
+        return toWTFStringSlowCase(exec);

     }
 
     }
 

-    inline UString JSValue::toPrimitiveString(ExecState* exec) const
+    ALWAYS_INLINE String inlineJSValueNotStringtoString(const JSValue& value, ExecState* exec)

     {
     {

-        ASSERT(!isString());
-        if (isInt32())
-            return exec->globalData().numericStrings.add(asInt32());
-        if (isDouble())
-            return exec->globalData().numericStrings.add(asDouble());
-        if (isTrue())
-            return "true";
-        if (isFalse())
-            return "false";
-        if (isNull())
-            return "null";
-        if (isUndefined())
-            return "undefined";
-        ASSERT(isCell());
-        return asCell()->toPrimitive(exec, NoPreference).toString(exec);
+        VM& vm = exec->vm();
+        if (value.isInt32())
+            return vm.numericStrings.add(value.asInt32());
+        if (value.isDouble())
+            return vm.numericStrings.add(value.asDouble());
+        if (value.isTrue())
+            return vm.propertyNames->trueKeyword.string();
+        if (value.isFalse())
+            return vm.propertyNames->falseKeyword.string();
+        if (value.isNull())
+            return vm.propertyNames->nullKeyword.string();
+        if (value.isUndefined())
+            return vm.propertyNames->undefinedKeyword.string();
+        return value.toString(exec)->value(exec);
+    }
+
+    ALWAYS_INLINE String JSValue::toWTFStringInline(ExecState* exec) const
+    {
+        if (isString())
+            return static_cast<JSString*>(asCell())->value(exec);
+
+        return inlineJSValueNotStringtoString(*this, exec);

     }
 
 } // namespace JSC
     }
 
 } // namespace JSC