Source/JavaScriptCore/runtime/JSValue.cpp

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

#include "BooleanConstructor.h"
#include "BooleanPrototype.h"
#include "Error.h"
#include "ExceptionHelpers.h"
#include "JSGlobalObject.h"
#include "JSFunction.h"
#include "JSNotAnObject.h"
#include "NumberObject.h"
#include <wtf/MathExtras.h>
#include <wtf/StringExtras.h>

namespace JSC {

static const double D32 = 4294967296.0;

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

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

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());
    throwError(exec, createNotAnObjectError(exec, *this));
    return new (exec) JSNotAnObject(exec);
}

JSObject* JSValue::toThisObjectSlowCase(ExecState* exec) const
{
    ASSERT(!isCell());

    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::synthesizeObject(ExecState* exec) const
{
    ASSERT(!isCell());
    if (isNumber())
        return constructNumber(exec, exec->lexicalGlobalObject(), asValue());
    if (isBoolean())
        return constructBooleanFromImmediateBoolean(exec, exec->lexicalGlobalObject(), asValue());

    ASSERT(isUndefinedOrNull());
    throwError(exec, createNotAnObjectError(exec, *this));
    return new (exec) JSNotAnObject(exec);
}

JSObject* JSValue::synthesizePrototype(ExecState* exec) const
{
    ASSERT(!isCell());
    if (isNumber())
        return exec->lexicalGlobalObject()->numberPrototype();
    if (isBoolean())
        return exec->lexicalGlobalObject()->booleanPrototype();

    ASSERT(isUndefinedOrNull());
    throwError(exec, createNotAnObjectError(exec, *this));
    return new (exec) JSNotAnObject(exec);
}

#ifndef NDEBUG
char* JSValue::description()
{
    static const size_t size = 32;
    static char description[size];

    if (!*this)
        snprintf(description, size, "<JSValue()>");
    else if (isInt32())
        snprintf(description, size, "Int32: %d", asInt32());
    else if (isDouble())
        snprintf(description, size, "Double: %lf", asDouble());
    else if (isCell())
        snprintf(description, size, "Cell: %p", asCell());
    else if (isTrue())
        snprintf(description, size, "True");
    else if (isFalse())
        snprintf(description, size, "False");
    else if (isNull())
        snprintf(description, size, "Null");
    else if (isUndefined())
        snprintf(description, size, "Undefined");
    else
        snprintf(description, size, "INVALID");

    return description;
}
#endif

// 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;
}

NEVER_INLINE double nonInlineNaN()
{
#if OS(SYMBIAN)
    return nanval();
#else
    return std::numeric_limits<double>::quiet_NaN();
#endif
}

bool JSValue::isValidCallee()
{
    return asObject(asObject(asCell())->getAnonymousValue(0))->isGlobalObject();
}

} // namespace JSC