JSString.h   [plain text]

/*
 *  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, 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
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Library General Public License for more details.
 *
 *  You should have received a copy of the GNU Library General Public License
 *  along with this library; see the file COPYING.LIB.  If not, write to
 *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 *  Boston, MA 02110-1301, USA.
 *
 */

#ifndef JSString_h
#define JSString_h

#include "CallFrame.h"
#include "CommonIdentifiers.h"
#include "Identifier.h"
#include "PropertyDescriptor.h"
#include "PropertySlot.h"
#include "Structure.h"
#include <array>

namespace JSC {

    class JSString;
    class JSRopeString;
    class LLIntOffsetsExtractor;

    JSString* jsEmptyString(VM*);
    JSString* jsEmptyString(ExecState*);
    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(VM*, UChar);
    JSString* jsSingleCharacterString(ExecState*, UChar);
    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(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 String
    JSString* jsOwnedString(VM*, const String&);
    JSString* jsOwnedString(ExecState*, const String&);

    JSRopeString* jsStringBuilder(VM*);

    class JSString : public JSCell {
    public:
        friend class JIT;
        friend class VM;
        friend class SpecializedThunkJIT;
        friend class JSRopeString;
        friend class MarkStack;
        friend class SlotVisitor;
        friend struct ThunkHelpers;

        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)
        {
        }

        JSString(VM& vm)
            : JSCell(vm, vm.stringStructure.get())
            , m_flags(0)
        {
        }

        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++;
        }

        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 < m_length; }
        JSString* getIndex(ExecState*, unsigned);

        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:
        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);
        }

        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());
        }

        static JSRopeString* createNull(VM& vm)
        {
            JSRopeString* newString = new (NotNull, allocateCell<JSRopeString>(vm.heap)) JSRopeString(vm);
            newString->finishCreation(vm);
            return newString;
        }

    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); }

        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;
    };


    inline const StringImpl* JSString::tryGetValueImpl() const
    {
        return m_value.impl();
    }

    JSString* asString(JSValue);

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

    inline JSString* jsEmptyString(VM* vm)
    {
        return vm->smallStrings.emptyString();
    }

    ALWAYS_INLINE JSString* jsSingleCharacterString(VM* vm, UChar c)
    {
        if (c <= maxSingleCharacterString)
            return vm->smallStrings.singleCharacterString(c);
        return JSString::create(*vm, String(&c, 1).impl());
    }

    ALWAYS_INLINE JSString* jsSingleCharacterSubstring(ExecState* exec, const String& s, unsigned offset)
    {
        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(VM* vm, const String& s)
    {
        ASSERT(s.length() > 1);
        return JSString::create(*vm, s.impl());
    }

    ALWAYS_INLINE Identifier JSString::toIdentifier(ExecState* exec) const
    {
        return Identifier(exec, toAtomicString(exec));
    }

    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));
        if (isRope())
            return static_cast<JSRopeString*>(this)->getIndexSlowCase(exec, i);
        ASSERT(i < m_value.length());
        return jsSingleCharacterSubstring(exec, m_value, i);
    }

    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());
    }

    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(this, DontEnum | DontDelete | ReadOnly, jsNumber(m_length));
            return true;
        }

        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 < 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 String JSValue::toWTFString(ExecState* exec) const
    {
        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

#endif // JSString_h