runtime/JSValue.cpp

   1 /*
   2  *  Copyright (C) 1999-2001 Harri Porten (porten@kde.org)
   3  *  Copyright (C) 2001 Peter Kelly (pmk@post.com)
   4  *  Copyright (C) 2003, 2007, 2008 Apple Inc. All rights reserved.
   5  *
   6  *  This library is free software; you can redistribute it and/or
   7  *  modify it under the terms of the GNU Library General Public
   8  *  License as published by the Free Software Foundation; either
   9  *  version 2 of the License, or (at your option) any later version.
  10  *
  11  *  This library is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  *  Library General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU Library General Public License
  17  *  along with this library; see the file COPYING.LIB.  If not, write to
  18  *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  19  *  Boston, MA 02110-1301, USA.
  20  *
  21  */
  22
  23 #include "config.h"
  24 #include "JSValue.h"
  25
  26 #include "BooleanConstructor.h"
  27 #include "BooleanPrototype.h"
  28 #include "Error.h"
  29 #include "ExceptionHelpers.h"
  30 #include "JSGlobalObject.h"
  31 #include "JSFunction.h"
  32 #include "JSNotAnObject.h"
  33 #include "NumberObject.h"
  34 #include <wtf/MathExtras.h>
  35 #include <wtf/StringExtras.h>
  36
  37 namespace JSC {
  38
  39 static const double D32 = 4294967296.0;
  40
  41 // ECMA 9.4
  42 double JSValue::toInteger(ExecState* exec) const
  43 {
  44     if (isInt32())
  45         return asInt32();
  46     double d = toNumber(exec);
  47     return isnan(d) ? 0.0 : trunc(d);
  48 }
  49
  50 double JSValue::toIntegerPreserveNaN(ExecState* exec) const
  51 {
  52     if (isInt32())
  53         return asInt32();
  54     return trunc(toNumber(exec));
  55 }
  56
  57 JSObject* JSValue::toObjectSlowCase(ExecState* exec, JSGlobalObject* globalObject) const
  58 {
  59     ASSERT(!isCell());
  60
  61     if (isInt32() || isDouble())
  62         return constructNumber(exec, globalObject, asValue());
  63     if (isTrue() || isFalse())
  64         return constructBooleanFromImmediateBoolean(exec, globalObject, asValue());
  65
  66     ASSERT(isUndefinedOrNull());
  67     throwError(exec, createNotAnObjectError(exec, *this));
  68     return new (exec) JSNotAnObject(exec);
  69 }
  70
  71 JSObject* JSValue::toThisObjectSlowCase(ExecState* exec) const
  72 {
  73     ASSERT(!isCell());
  74
  75     if (isInt32() || isDouble())
  76         return constructNumber(exec, exec->lexicalGlobalObject(), asValue());
  77     if (isTrue() || isFalse())
  78         return constructBooleanFromImmediateBoolean(exec, exec->lexicalGlobalObject(), asValue());
  79     ASSERT(isUndefinedOrNull());
  80     return exec->globalThisValue();
  81 }
  82
  83 JSObject* JSValue::synthesizeObject(ExecState* exec) const
  84 {
  85     ASSERT(!isCell());
  86     if (isNumber())
  87         return constructNumber(exec, exec->lexicalGlobalObject(), asValue());
  88     if (isBoolean())
  89         return constructBooleanFromImmediateBoolean(exec, exec->lexicalGlobalObject(), asValue());
  90
  91     ASSERT(isUndefinedOrNull());
  92     throwError(exec, createNotAnObjectError(exec, *this));
  93     return new (exec) JSNotAnObject(exec);
  94 }
  95
  96 JSObject* JSValue::synthesizePrototype(ExecState* exec) const
  97 {
  98     ASSERT(!isCell());
  99     if (isNumber())
 100         return exec->lexicalGlobalObject()->numberPrototype();
 101     if (isBoolean())
 102         return exec->lexicalGlobalObject()->booleanPrototype();
 103
 104     ASSERT(isUndefinedOrNull());
 105     throwError(exec, createNotAnObjectError(exec, *this));
 106     return new (exec) JSNotAnObject(exec);
 107 }
 108
 109 #ifndef NDEBUG
 110 char* JSValue::description()
 111 {
 112     static const size_t size = 32;
 113     static char description[size];
 114
 115     if (!*this)
 116         snprintf(description, size, "<JSValue()>");
 117     else if (isInt32())
 118         snprintf(description, size, "Int32: %d", asInt32());
 119     else if (isDouble())
 120         snprintf(description, size, "Double: %lf", asDouble());
 121     else if (isCell())
 122         snprintf(description, size, "Cell: %p", asCell());
 123     else if (isTrue())
 124         snprintf(description, size, "True");
 125     else if (isFalse())
 126         snprintf(description, size, "False");
 127     else if (isNull())
 128         snprintf(description, size, "Null");
 129     else if (isUndefined())
 130         snprintf(description, size, "Undefined");
 131     else
 132         snprintf(description, size, "INVALID");
 133
 134     return description;
 135 }
 136 #endif
 137
 138 // This in the ToInt32 operation is defined in section 9.5 of the ECMA-262 spec.
 139 // Note that this operation is identical to ToUInt32 other than to interpretation
 140 // of the resulting bit-pattern (as such this metod is also called to implement
 141 // ToUInt32).
 142 //
 143 // The operation can be descibed as round towards zero, then select the 32 least
 144 // bits of the resulting value in 2s-complement representation.
 145 int32_t toInt32(double number)
 146 {
 147     int64_t bits = WTF::bitwise_cast<int64_t>(number);
 148     int32_t exp = (static_cast<int32_t>(bits >> 52) & 0x7ff) - 0x3ff;
 149
 150     // If exponent < 0 there will be no bits to the left of the decimal point
 151     // after rounding; if the exponent is > 83 then no bits of precision can be
 152     // left in the low 32-bit range of the result (IEEE-754 doubles have 52 bits
 153     // of fractional precision).
 154     // Note this case handles 0, -0, and all infinte, NaN, & denormal value.
 155     if (exp < 0 || exp > 83)
 156         return 0;
 157
 158     // Select the appropriate 32-bits from the floating point mantissa.  If the
 159     // exponent is 52 then the bits we need to select are already aligned to the
 160     // lowest bits of the 64-bit integer representation of tghe number, no need
 161     // to shift.  If the exponent is greater than 52 we need to shift the value
 162     // left by (exp - 52), if the value is less than 52 we need to shift right
 163     // accordingly.
 164     int32_t result = (exp > 52)
 165         ? static_cast<int32_t>(bits << (exp - 52))
 166         : static_cast<int32_t>(bits >> (52 - exp));
 167
 168     // IEEE-754 double precision values are stored omitting an implicit 1 before
 169     // the decimal point; we need to reinsert this now.  We may also the shifted
 170     // invalid bits into the result that are not a part of the mantissa (the sign
 171     // and exponent bits from the floatingpoint representation); mask these out.
 172     if (exp < 32) {
 173         int32_t missingOne = 1 << exp;
 174         result &= missingOne - 1;
 175         result += missingOne;
 176     }
 177
 178     // If the input value was negative (we could test either 'number' or 'bits',
 179     // but testing 'bits' is likely faster) invert the result appropriately.
 180     return bits < 0 ? -result : result;
 181 }
 182
 183 NEVER_INLINE double nonInlineNaN()
 184 {
 185 #if OS(SYMBIAN)
 186     return nanval();
 187 #else
 188     return std::numeric_limits<double>::quiet_NaN();
 189 #endif
 190 }
 191
 192 bool JSValue::isValidCallee()
 193 {
 194     return asObject(asObject(asCell())->getAnonymousValue(0))->isGlobalObject();
 195 }
 196
 197 } // namespace JSC