]> git.saurik.com Git - apple/javascriptcore.git/blobdiff - runtime/JSString.h
JavaScriptCore-7600.1.4.11.8.tar.gz
[apple/javascriptcore.git] / runtime / JSString.h
index e4baa73aba9809c7c753808f5fad107899304c40..1287b66bee4a9ef4f89b122b6d7c7b37f294af7a 100644 (file)
@@ -1,7 +1,7 @@
 /*
  *  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
 #ifndef JSString_h
 #define JSString_h
 
-#include "CommonIdentifiers.h"
 #include "CallFrame.h"
+#include "CommonIdentifiers.h"
 #include "Identifier.h"
-#include "JSNumberCell.h"
+#include "PropertyDescriptor.h"
 #include "PropertySlot.h"
+#include "Structure.h"
+#include <array>
 
 namespace JSC {
 
     class JSString;
+    class JSRopeString;
+    class LLIntOffsetsExtractor;
 
-    JSString* jsEmptyString(JSGlobalData*);
+    JSString* jsEmptyString(VM*);
     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* jsSingleCharacterSubstring(JSGlobalData*, const UString&, unsigned offset);
-    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.
-    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
-    // 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&);
+
+    JSRopeString* jsStringBuilder(VM*);
 
     class JSString : public JSCell {
+    public:
         friend class JIT;
-        friend class Interpreter;
+        friend class VM;
+        friend class SpecializedThunkJIT;
+        friend class JSRopeString;
+        friend class MarkStack;
+        friend class SlotVisitor;
+        friend struct ThunkHelpers;
 
-    public:
-        JSString(JSGlobalData* globalData, const UString& value)
-            : JSCell(globalData->stringStructure.get())
+        typedef JSCell Base;
+
+        static const bool needsDestruction = true;
+        static const bool hasImmortalStructure = true;
+        static void destroy(JSCell*);
+
+    private:
+        JSString(VM& vm, PassRefPtr<StringImpl> value)
+            : JSCell(vm, vm.stringStructure.get())
+            , m_flags(0)
             , m_value(value)
         {
-            Heap::heap(this)->reportExtraMemoryCost(value.cost());
         }
 
-        enum HasOtherOwnerType { HasOtherOwner };
-        JSString(JSGlobalData* globalData, const UString& value, HasOtherOwnerType)
-            : JSCell(globalData->stringStructure.get())
-            , m_value(value)
+        JSString(VM& vm)
+            : JSCell(vm, vm.stringStructure.get())
+            , m_flags(0)
         {
         }
-        JSString(JSGlobalData* globalData, PassRefPtr<UString::Rep> value, HasOtherOwnerType)
-            : JSCell(globalData->stringStructure.get())
-            , m_value(value)
+
+        void finishCreation(VM& vm, size_t length)
         {
+            ASSERT(!m_value.isNull());
+            Base::finishCreation(vm);
+            m_length = length;
+            setIs8Bit(m_value.impl()->is8Bit());
+            vm.m_newStringsSinceLastHashCons++;
         }
-        
-        const UString& value() const { return m_value; }
 
-        bool getStringPropertySlot(ExecState*, const Identifier& propertyName, PropertySlot&);
+        void finishCreation(VM& vm, size_t length, size_t cost)
+        {
+            ASSERT(!m_value.isNull());
+            Base::finishCreation(vm);
+            m_length = length;
+            setIs8Bit(m_value.impl()->is8Bit());
+            Heap::heap(this)->reportExtraMemoryCost(cost);
+            vm.m_newStringsSinceLastHashCons++;
+        }
+
+    protected:
+        void finishCreation(VM& vm)
+        {
+            Base::finishCreation(vm);
+            m_length = 0;
+            setIs8Bit(true);
+            vm.m_newStringsSinceLastHashCons++;
+        }
+            
+    public:
+        static JSString* create(VM& vm, PassRefPtr<StringImpl> value)
+        {
+            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;
+        }
+        static JSString* createHasOtherOwner(VM& vm, PassRefPtr<StringImpl> value)
+        {
+            ASSERT(value);
+            size_t length = value->length();
+            JSString* newString = new (NotNull, allocateCell<JSString>(vm.heap)) JSString(vm, value);
+            newString->finishCreation(vm, length);
+            return newString;
+        }
+
+        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 < static_cast<unsigned>(m_value.size()); }
-        JSString* getIndex(JSGlobalData*, unsigned);
+        bool canGetIndex(unsigned i) { return i < m_length; }
+        JSString* getIndex(ExecState*, unsigned);
 
-        static PassRefPtr<Structure> createStructure(JSValuePtr proto) { return Structure::create(proto, TypeInfo(StringType, NeedsThisConversion)); }
+        static Structure* createStructure(VM& vm, JSGlobalObject* globalObject, JSValue proto)
+        {
+            return Structure::create(vm, globalObject, proto, TypeInfo(StringType, StructureFlags), info());
+        }
+
+        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)
+        {
+            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*);
+
+        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:
-        enum VPtrStealingHackType { VPtrStealingHack };
-        JSString(VPtrStealingHackType) 
-            : JSCell(0)
+        JSRopeString(VM& vm)
+            : JSString(vm)
+        {
+        }
+
+        void finishCreation(VM& vm, JSString* s1, JSString* s2)
+        {
+            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);
+        }
+            
+        void finishCreation(VM& vm, JSString* s1, JSString* s2, JSString* s3)
+        {
+            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);
+        }
+
+        void finishCreation(VM& vm)
         {
+            JSString::finishCreation(vm);
         }
 
-        virtual JSValuePtr toPrimitive(ExecState*, PreferredPrimitiveType) const;
-        virtual bool getPrimitiveNumber(ExecState*, double& number, JSValuePtr& value);
-        virtual bool toBoolean(ExecState*) const;
-        virtual double toNumber(ExecState*) const;
-        virtual JSObject* toObject(ExecState*) const;
-        virtual UString toString(ExecState*) const;
+        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());
+        }
 
-        virtual JSObject* toThisObject(ExecState*) const;
-        virtual UString toThisString(ExecState*) const;
-        virtual JSString* toThisJSString(ExecState*);
+        static JSRopeString* createNull(VM& vm)
+        {
+            JSRopeString* newString = new (NotNull, allocateCell<JSRopeString>(vm.heap)) JSRopeString(vm);
+            newString->finishCreation(vm);
+            return newString;
+        }
 
-        // Actually getPropertySlot, not getOwnPropertySlot (see JSCell).
-        virtual bool getOwnPropertySlot(ExecState*, const Identifier& propertyName, PropertySlot&);
-        virtual bool getOwnPropertySlot(ExecState*, unsigned propertyName, PropertySlot&);
+    public:
+        static JSString* create(VM& vm, JSString* s1, JSString* s2)
+        {
+            JSRopeString* newString = new (NotNull, allocateCell<JSRopeString>(vm.heap)) JSRopeString(vm);
+            newString->finishCreation(vm, s1, s2);
+            return newString;
+        }
+        static JSString* create(VM& vm, JSString* s1, JSString* s2, JSString* s3)
+        {
+            JSRopeString* newString = new (NotNull, allocateCell<JSRopeString>(vm.heap)) JSRopeString(vm);
+            newString->finishCreation(vm, s1, s2, s3);
+            return newString;
+        }
+
+        void visitFibers(SlotVisitor&);
+            
+        static ptrdiff_t offsetOfFibers() { return OBJECT_OFFSETOF(JSRopeString, m_fibers); }
 
-        UString m_value;
+        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);
+
+        mutable std::array<WriteBarrier<JSString>, s_maxInternalRopeLength> m_fibers;
     };
 
-    JSString* asString(JSValuePtr);
 
-    inline JSString* asString(JSValuePtr value)
+    inline const StringImpl* JSString::tryGetValueImpl() const
+    {
+        return m_value.impl();
+    }
+
+    JSString* asString(JSValue);
+
+    inline JSString* asString(JSValue value)
     {
-        ASSERT(asCell(value)->isString());
-        return static_cast<JSString*>(asCell(value));
+        ASSERT(value.asCell()->isString());
+        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 <= 0xFF)
-            return globalData->smallStrings.singleCharacterString(globalData, c);
-        return new (globalData) JSString(globalData, UString(&c, 1));
+        if (c <= maxSingleCharacterString)
+            return vm->smallStrings.singleCharacterString(c);
+        return JSString::create(*vm, String(&c, 1).impl());
     }
 
-    inline JSString* jsSingleCharacterSubstring(JSGlobalData* globalData, const UString& s, unsigned offset)
+    ALWAYS_INLINE JSString* jsSingleCharacterSubstring(ExecState* exec, const String& s, unsigned offset)
     {
-        ASSERT(offset < static_cast<unsigned>(s.size()));
-        UChar c = s.data()[offset];
-        if (c <= 0xFF)
-            return globalData->smallStrings.singleCharacterString(globalData, c);
-        return new (globalData) JSString(globalData, UString::Rep::create(s.rep(), offset, 1));
+        VM* vm = &exec->vm();
+        ASSERT(offset < static_cast<unsigned>(s.length()));
+        UChar c = s.characterAt(offset);
+        if (c <= maxSingleCharacterString)
+            return vm->smallStrings.singleCharacterString(c);
+        return JSString::create(*vm, StringImpl::createSubstringSharingImpl(s.impl(), offset, 1));
     }
 
-    inline JSString* jsNontrivialString(JSGlobalData* globalData, const char* s)
+    inline JSString* jsNontrivialString(VM* vm, const String& s)
     {
-        ASSERT(s);
-        ASSERT(s[0]);
-        ASSERT(s[1]);
-        return new (globalData) JSString(globalData, s);
+        ASSERT(s.length() > 1);
+        return JSString::create(*vm, s.impl());
     }
 
-    inline JSString* jsNontrivialString(JSGlobalData* globalData, const UString& s)
+    ALWAYS_INLINE Identifier JSString::toIdentifier(ExecState* exec) const
     {
-        ASSERT(s.size() > 1);
-        return new (globalData) JSString(globalData, s);
+        return Identifier(exec, toAtomicString(exec));
     }
 
-    inline JSString* JSString::getIndex(JSGlobalData* globalData, unsigned i)
+    ALWAYS_INLINE AtomicString JSString::toAtomicString(ExecState* exec) const
+    {
+        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));
-        return jsSingleCharacterSubstring(globalData, m_value, i);
+        if (isRope())
+            return static_cast<JSRopeString*>(this)->getIndexSlowCase(exec, i);
+        ASSERT(i < m_value.length());
+        return jsSingleCharacterSubstring(exec, m_value, i);
     }
 
-    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* jsSingleCharacterSubstring(ExecState* exec, const UString& s, unsigned offset) { return jsSingleCharacterSubstring(&exec->globalData(), s, offset); }
-    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 JSString* jsString(VM* vm, const String& s)
+    {
+        int size = s.length();
+        if (!size)
+            return vm->smallStrings.emptyString();
+        if (size == 1) {
+            UChar c = s.characterAt(0);
+            if (c <= maxSingleCharacterString)
+                return vm->smallStrings.singleCharacterString(c);
+        }
+        return JSString::create(*vm, s.impl());
+    }
+
+    inline JSString* jsSubstring(ExecState* exec, JSString* 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()));
+        VM* vm = &exec->vm();
+        if (!length)
+            return vm->smallStrings.emptyString();
+        return jsSubstring(vm, s->value(exec), offset, 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)
+            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::createSubstringSharingImpl8(s.impl(), offset, length));
+    }
+
+    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)
+            return vm->smallStrings.emptyString();
+        if (size == 1) {
+            UChar c = s.characterAt(0);
+            if (c <= maxSingleCharacterString)
+                return vm->smallStrings.singleCharacterString(c);
+        }
+        return JSString::createHasOtherOwner(*vm, s.impl());
+    }
 
-    ALWAYS_INLINE bool JSString::getStringPropertySlot(ExecState* exec, const Identifier& propertyName, PropertySlot& slot)
+    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, PropertyName propertyName, PropertySlot& slot)
     {
         if (propertyName == exec->propertyNames().length) {
-            slot.setValue(jsNumber(exec, m_value.size()));
+            slot.setValue(this, DontEnum | DontDelete | ReadOnly, jsNumber(m_length));
             return true;
         }
 
-        bool isStrictUInt32;
-        unsigned i = propertyName.toStrictUInt32(&isStrictUInt32);
-        if (isStrictUInt32 && i < static_cast<unsigned>(m_value.size())) {
-            slot.setValue(jsSingleCharacterSubstring(exec, m_value, 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;
     }
-        
+            
     ALWAYS_INLINE bool JSString::getStringPropertySlot(ExecState* exec, unsigned propertyName, PropertySlot& slot)
     {
-        if (propertyName < static_cast<unsigned>(m_value.size())) {
-            slot.setValue(jsSingleCharacterSubstring(exec, m_value, propertyName));
+        if (propertyName < m_length) {
+            slot.setValue(this, DontDelete | ReadOnly, getIndex(exec, propertyName));
             return true;
         }
 
         return false;
     }
 
+    inline bool isJSString(JSValue v) { return v.isCell() && v.asCell()->type() == StringType; }
+
     // --- 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 JSString* JSValuePtr::toThisJSString(ExecState* exec)
+    inline String JSValue::toWTFString(ExecState* exec) const
     {
-        return JSImmediate::isImmediate(asValue()) ? jsString(exec, JSImmediate::toString(asValue())) : asCell()->toThisJSString(exec);
+        if (isString())
+            return static_cast<JSString*>(asCell())->value(exec);
+        return toWTFStringSlowCase(exec);
+    }
+
+    ALWAYS_INLINE String inlineJSValueNotStringtoString(const JSValue& value, ExecState* 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