Source/JavaScriptCore/runtime/JSCJSValue.cpp

/*
 *  Copyright (C) 1999-2001 Harri Porten (porten@kde.org)
 *  Copyright (C) 2001 Peter Kelly (pmk@post.com)
 *  Copyright (C) 2003, 2007, 2008, 2012 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.
 *
 */

#include "config.h"
#include "JSCJSValue.h"

#include "BooleanConstructor.h"
#include "BooleanPrototype.h"
#include "CustomGetterSetter.h"
#include "Error.h"
#include "ExceptionHelpers.h"
#include "GetterSetter.h"
#include "JSCJSValueInlines.h"
#include "JSFunction.h"
#include "JSGlobalObject.h"
#include "NumberObject.h"
#include "StructureInlines.h"
#include <wtf/MathExtras.h>
#include <wtf/StringExtras.h>

namespace JSC {

// ECMA 9.4
double JSValue::toInteger(ExecState* exec) const
{
    if (isInt32())
        return asInt32();
    double d = toNumber(exec);
    return std::isnan(d) ? 0.0 : trunc(d);
}

double JSValue::toIntegerPreserveNaN(ExecState* exec) const
{
    if (isInt32())
        return asInt32();
    return trunc(toNumber(exec));
}

double JSValue::toLength(ExecState* exec) const
{
    // ECMA 7.1.15
    // http://www.ecma-international.org/ecma-262/6.0/#sec-tolength
    double d = toInteger(exec);
    if (d <= 0)
        return 0.0;
    if (std::isinf(d))
        return 9007199254740991.0; // 2 ** 53 - 1
    return std::min(d, 9007199254740991.0);
}

double JSValue::toNumberSlowCase(ExecState* exec) const
{
    ASSERT(!isInt32() && !isDouble());
    if (isCell())
        return asCell()->toNumber(exec);
    if (isTrue())
        return 1.0;
    return isUndefined() ? PNaN : 0; // null and false both convert to 0.
}

JSObject* JSValue::toObjectSlowCase(ExecState* exec, JSGlobalObject* globalObject) const
{
    ASSERT(!isCell());

    if (isInt32() || isDouble())
        return constructNumber(exec, globalObject, asValue());
    if (isTrue() || isFalse())
        return constructBooleanFromImmediateBoolean(exec, globalObject, asValue());

    ASSERT(isUndefinedOrNull());
    VM& vm = exec->vm();
    vm.throwException(exec, createNotAnObjectError(exec, *this));
    return nullptr;
}

JSValue JSValue::toThisSlowCase(ExecState* exec, ECMAMode ecmaMode) const
{
    ASSERT(!isCell());

    if (ecmaMode == StrictMode)
        return *this;

    if (isInt32() || isDouble())
        return constructNumber(exec, exec->lexicalGlobalObject(), asValue());
    if (isTrue() || isFalse())
        return constructBooleanFromImmediateBoolean(exec, exec->lexicalGlobalObject(), asValue());
    ASSERT(isUndefinedOrNull());
    return exec->globalThisValue();
}

JSObject* JSValue::synthesizePrototype(ExecState* exec) const
{
    if (isCell()) {
        if (isString())
            return exec->lexicalGlobalObject()->stringPrototype();
        ASSERT(isSymbol());
        return exec->lexicalGlobalObject()->symbolPrototype();
    }

    if (isNumber())
        return exec->lexicalGlobalObject()->numberPrototype();
    if (isBoolean())
        return exec->lexicalGlobalObject()->booleanPrototype();

    ASSERT(isUndefinedOrNull());
    VM& vm = exec->vm();
    vm.throwException(exec, createNotAnObjectError(exec, *this));
    return nullptr;
}

// ECMA 8.7.2
bool JSValue::putToPrimitive(ExecState* exec, PropertyName propertyName, JSValue value, PutPropertySlot& slot)
{
    VM& vm = exec->vm();

    if (Optional<uint32_t> index = parseIndex(propertyName))
        return putToPrimitiveByIndex(exec, index.value(), value, slot.isStrictMode());

    // Check if there are any setters or getters in the prototype chain
    JSObject* obj = synthesizePrototype(exec);
    if (UNLIKELY(!obj))
        return false;
    JSValue prototype;
    if (propertyName != exec->propertyNames().underscoreProto) {
        for (; !obj->structure()->hasReadOnlyOrGetterSetterPropertiesExcludingProto(); obj = asObject(prototype)) {
            prototype = obj->getPrototypeDirect();
            if (prototype.isNull()) {
                if (slot.isStrictMode())
                    throwTypeError(exec, StrictModeReadonlyPropertyWriteError);
                return false;
            }
        }
    }

    for (; ; obj = asObject(prototype)) {
        unsigned attributes;
        PropertyOffset offset = obj->structure()->get(vm, propertyName, attributes);
        if (offset != invalidOffset) {
            if (attributes & ReadOnly) {
                if (slot.isStrictMode())
                    exec->vm().throwException(exec, createTypeError(exec, StrictModeReadonlyPropertyWriteError));
                return false;
            }

            JSValue gs = obj->getDirect(offset);
            if (gs.isGetterSetter())
                return callSetter(exec, *this, gs, value, slot.isStrictMode() ? StrictMode : NotStrictMode);

            if (gs.isCustomGetterSetter())
                return callCustomSetter(exec, gs, attributes & CustomAccessor, obj, slot.thisValue(), value);

            // If there's an existing property on the object or one of its 
            // prototypes it should be replaced, so break here.
            break;
        }

        prototype = obj->getPrototype(vm, exec);
        if (vm.exception())
            return false;
        if (prototype.isNull())
            break;
    }
    
    if (slot.isStrictMode())
        throwTypeError(exec, StrictModeReadonlyPropertyWriteError);
    return false;
}

bool JSValue::putToPrimitiveByIndex(ExecState* exec, unsigned propertyName, JSValue value, bool shouldThrow)
{
    if (propertyName > MAX_ARRAY_INDEX) {
        PutPropertySlot slot(*this, shouldThrow);
        return putToPrimitive(exec, Identifier::from(exec, propertyName), value, slot);
    }
    
    JSObject* prototype = synthesizePrototype(exec);
    if (UNLIKELY(!prototype)) {
        ASSERT(exec->hadException());
        return false;
    }
    bool putResult = false;
    if (prototype->attemptToInterceptPutByIndexOnHoleForPrototype(exec, *this, propertyName, value, shouldThrow, putResult))
        return putResult;
    
    if (shouldThrow)
        throwTypeError(exec, StrictModeReadonlyPropertyWriteError);
    return false;
}

void JSValue::dump(PrintStream& out) const
{
    dumpInContext(out, 0);
}

void JSValue::dumpInContext(PrintStream& out, DumpContext* context) const
{
    dumpInContextAssumingStructure(
        out, context, (!!*this && isCell()) ? asCell()->structure() : nullptr);
}

void JSValue::dumpInContextAssumingStructure(
    PrintStream& out, DumpContext* context, Structure* structure) const
{
    if (!*this)
        out.print("<JSValue()>");
    else if (isInt32())
        out.printf("Int32: %d", asInt32());
    else if (isDouble()) {
#if USE(JSVALUE64)
        out.printf("Double: %lld, %lf", (long long)reinterpretDoubleToInt64(asDouble()), asDouble());
#else
        union {
            double asDouble;
            uint32_t asTwoInt32s[2];
        } u;
        u.asDouble = asDouble();
        out.printf("Double: %08x:%08x, %lf", u.asTwoInt32s[1], u.asTwoInt32s[0], asDouble());
#endif
    } else if (isCell()) {
        if (structure->classInfo()->isSubClassOf(JSString::info())) {
            JSString* string = jsCast<JSString*>(asCell());
            out.print("String");
            if (string->isRope())
                out.print(" (rope)");
            const StringImpl* impl = string->tryGetValueImpl();
            if (impl) {
                if (impl->isAtomic())
                    out.print(" (atomic)");
                if (impl->isAtomic())
                    out.print(" (identifier)");
                if (impl->isSymbol())
                    out.print(" (symbol)");
            } else
                out.print(" (unresolved)");
            out.print(": ", impl);
        } else if (structure->classInfo()->isSubClassOf(Structure::info()))
            out.print("Structure: ", inContext(*jsCast<Structure*>(asCell()), context));
        else {
            out.print("Cell: ", RawPointer(asCell()));
            out.print(" (", inContext(*structure, context), ")");
        }
#if USE(JSVALUE64)
        out.print(", ID: ", asCell()->structureID());
#endif
    } else if (isTrue())
        out.print("True");
    else if (isFalse())
        out.print("False");
    else if (isNull())
        out.print("Null");
    else if (isUndefined())
        out.print("Undefined");
    else
        out.print("INVALID");
}

void JSValue::dumpForBacktrace(PrintStream& out) const
{
    if (!*this)
        out.print("<JSValue()>");
    else if (isInt32())
        out.printf("%d", asInt32());
    else if (isDouble())
        out.printf("%lf", asDouble());
    else if (isCell()) {
        if (asCell()->inherits(JSString::info())) {
            JSString* string = jsCast<JSString*>(asCell());
            const StringImpl* impl = string->tryGetValueImpl();
            if (impl)
                out.print("\"", impl, "\"");
            else
                out.print("(unresolved string)");
        } else if (asCell()->inherits(Structure::info())) {
            out.print("Structure[ ", asCell()->structure()->classInfo()->className);
#if USE(JSVALUE64)
            out.print(" ID: ", asCell()->structureID());
#endif
            out.print("]: ", RawPointer(asCell()));
        } else {
            out.print("Cell[", asCell()->structure()->classInfo()->className);
#if USE(JSVALUE64)
            out.print(" ID: ", asCell()->structureID());
#endif
            out.print("]: ", RawPointer(asCell()));
        }
    } else if (isTrue())
        out.print("True");
    else if (isFalse())
        out.print("False");
    else if (isNull())
        out.print("Null");
    else if (isUndefined())
        out.print("Undefined");
    else
        out.print("INVALID");
}

// This in the ToInt32 operation is defined in section 9.5 of the ECMA-262 spec.
// Note that this operation is identical to ToUInt32 other than to interpretation
// of the resulting bit-pattern (as such this metod is also called to implement
// ToUInt32).
//
// The operation can be descibed as round towards zero, then select the 32 least
// bits of the resulting value in 2s-complement representation.
int32_t toInt32(double number)
{
    int64_t bits = WTF::bitwise_cast<int64_t>(number);
    int32_t exp = (static_cast<int32_t>(bits >> 52) & 0x7ff) - 0x3ff;

    // If exponent < 0 there will be no bits to the left of the decimal point
    // after rounding; if the exponent is > 83 then no bits of precision can be
    // left in the low 32-bit range of the result (IEEE-754 doubles have 52 bits
    // of fractional precision).
    // Note this case handles 0, -0, and all infinte, NaN, & denormal value. 
    if (exp < 0 || exp > 83)
        return 0;

    // Select the appropriate 32-bits from the floating point mantissa.  If the
    // exponent is 52 then the bits we need to select are already aligned to the
    // lowest bits of the 64-bit integer representation of tghe number, no need
    // to shift.  If the exponent is greater than 52 we need to shift the value
    // left by (exp - 52), if the value is less than 52 we need to shift right
    // accordingly.
    int32_t result = (exp > 52)
        ? static_cast<int32_t>(bits << (exp - 52))
        : static_cast<int32_t>(bits >> (52 - exp));

    // IEEE-754 double precision values are stored omitting an implicit 1 before
    // the decimal point; we need to reinsert this now.  We may also the shifted
    // invalid bits into the result that are not a part of the mantissa (the sign
    // and exponent bits from the floatingpoint representation); mask these out.
    if (exp < 32) {
        int32_t missingOne = 1 << exp;
        result &= missingOne - 1;
        result += missingOne;
    }

    // If the input value was negative (we could test either 'number' or 'bits',
    // but testing 'bits' is likely faster) invert the result appropriately.
    return bits < 0 ? -result : result;
}

bool JSValue::isValidCallee()
{
    return asObject(asCell())->globalObject();
}

JSString* JSValue::toStringSlowCase(ExecState* exec, bool returnEmptyStringOnError) const
{
    auto errorValue = [&] () -> JSString* {
        if (returnEmptyStringOnError)
            return jsEmptyString(exec);
        return nullptr;
    };
    
    VM& vm = exec->vm();
    ASSERT(!isString());
    if (isInt32()) {
        auto integer = asInt32();
        if (static_cast<unsigned>(integer) <= 9)
            return vm.smallStrings.singleCharacterString(integer + '0');
        return jsNontrivialString(&vm, vm.numericStrings.add(integer));
    }
    if (isDouble())
        return jsString(&vm, vm.numericStrings.add(asDouble()));
    if (isTrue())
        return vm.smallStrings.trueString();
    if (isFalse())
        return vm.smallStrings.falseString();
    if (isNull())
        return vm.smallStrings.nullString();
    if (isUndefined())
        return vm.smallStrings.undefinedString();
    if (isSymbol()) {
        throwTypeError(exec, "Cannot convert a symbol to a string");
        return errorValue();
    }

    ASSERT(isCell());
    JSValue value = asCell()->toPrimitive(exec, PreferString);
    if (vm.exception())
        return errorValue();
    ASSERT(!value.isObject());
    JSString* result = value.toString(exec);
    if (vm.exception())
        return errorValue();
    return result;
}

String JSValue::toWTFStringSlowCase(ExecState* exec) const
{
    VM& vm = exec->vm();
    if (isInt32())
        return vm.numericStrings.add(asInt32());
    if (isDouble())
        return vm.numericStrings.add(asDouble());
    if (isTrue())
        return vm.propertyNames->trueKeyword.string();
    if (isFalse())
        return vm.propertyNames->falseKeyword.string();
    if (isNull())
        return vm.propertyNames->nullKeyword.string();
    if (isUndefined())
        return vm.propertyNames->undefinedKeyword.string();
    return toString(exec)->value(exec);
}

} // namespace JSC