runtime/JSCell.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 "JSCell.h"
  25
  26 #include "JSFunction.h"
  27 #include "JSString.h"
  28 #include "JSObject.h"
  29 #include <wtf/MathExtras.h>
  30
  31 namespace JSC {
  32
  33 #if defined NAN && defined INFINITY
  34
  35 extern const double NaN = NAN;
  36 extern const double Inf = INFINITY;
  37
  38 #else // !(defined NAN && defined INFINITY)
  39
  40 // The trick is to define the NaN and Inf globals with a different type than the declaration.
  41 // This trick works because the mangled name of the globals does not include the type, although
  42 // I'm not sure that's guaranteed. There could be alignment issues with this, since arrays of
  43 // characters don't necessarily need the same alignment doubles do, but for now it seems to work.
  44 // It would be good to figure out a 100% clean way that still avoids code that runs at init time.
  45
  46 // Note, we have to use union to ensure alignment. Otherwise, NaN_Bytes can start anywhere,
  47 // while NaN_double has to be 4-byte aligned for 32-bits.
  48 // With -fstrict-aliasing enabled, unions are the only safe way to do type masquerading.
  49
  50 static const union {
  51     struct {
  52         unsigned char NaN_Bytes[8];
  53         unsigned char Inf_Bytes[8];
  54     } bytes;
  55
  56     struct {
  57         double NaN_Double;
  58         double Inf_Double;
  59     } doubles;
  60
  61 } NaNInf = { {
  62 #if CPU(BIG_ENDIAN)
  63     { 0x7f, 0xf8, 0, 0, 0, 0, 0, 0 },
  64     { 0x7f, 0xf0, 0, 0, 0, 0, 0, 0 }
  65 #elif CPU(MIDDLE_ENDIAN)
  66     { 0, 0, 0xf8, 0x7f, 0, 0, 0, 0 },
  67     { 0, 0, 0xf0, 0x7f, 0, 0, 0, 0 }
  68 #else
  69     { 0, 0, 0, 0, 0, 0, 0xf8, 0x7f },
  70     { 0, 0, 0, 0, 0, 0, 0xf0, 0x7f }
  71 #endif
  72 } } ;
  73
  74 extern const double NaN = NaNInf.doubles.NaN_Double;
  75 extern const double Inf = NaNInf.doubles.Inf_Double;
  76
  77 #endif // !(defined NAN && defined INFINITY)
  78
  79 const ClassInfo JSCell::s_dummyCellInfo = { "DummyCell", 0, 0, 0 };
  80
  81 bool JSCell::getUInt32(uint32_t&) const
  82 {
  83     return false;
  84 }
  85
  86 bool JSCell::getString(ExecState* exec, UString&stringValue) const
  87 {
  88     if (!isString())
  89         return false;
  90     stringValue = static_cast<const JSString*>(this)->value(exec);
  91     return true;
  92 }
  93
  94 UString JSCell::getString(ExecState* exec) const
  95 {
  96     return isString() ? static_cast<const JSString*>(this)->value(exec) : UString();
  97 }
  98
  99 JSObject* JSCell::getObject()
 100 {
 101     return isObject() ? asObject(this) : 0;
 102 }
 103
 104 const JSObject* JSCell::getObject() const
 105 {
 106     return isObject() ? static_cast<const JSObject*>(this) : 0;
 107 }
 108
 109 CallType JSCell::getCallData(CallData&)
 110 {
 111     return CallTypeNone;
 112 }
 113
 114 ConstructType JSCell::getConstructData(ConstructData&)
 115 {
 116     return ConstructTypeNone;
 117 }
 118
 119 bool JSCell::getOwnPropertySlot(ExecState* exec, const Identifier& identifier, PropertySlot& slot)
 120 {
 121     // This is not a general purpose implementation of getOwnPropertySlot.
 122     // It should only be called by JSValue::get.
 123     // It calls getPropertySlot, not getOwnPropertySlot.
 124     JSObject* object = toObject(exec, exec->lexicalGlobalObject());
 125     slot.setBase(object);
 126     if (!object->getPropertySlot(exec, identifier, slot))
 127         slot.setUndefined();
 128     return true;
 129 }
 130
 131 bool JSCell::getOwnPropertySlot(ExecState* exec, unsigned identifier, PropertySlot& slot)
 132 {
 133     // This is not a general purpose implementation of getOwnPropertySlot.
 134     // It should only be called by JSValue::get.
 135     // It calls getPropertySlot, not getOwnPropertySlot.
 136     JSObject* object = toObject(exec, exec->lexicalGlobalObject());
 137     slot.setBase(object);
 138     if (!object->getPropertySlot(exec, identifier, slot))
 139         slot.setUndefined();
 140     return true;
 141 }
 142
 143 void JSCell::put(ExecState* exec, const Identifier& identifier, JSValue value, PutPropertySlot& slot)
 144 {
 145     toObject(exec, exec->lexicalGlobalObject())->put(exec, identifier, value, slot);
 146 }
 147
 148 void JSCell::put(ExecState* exec, unsigned identifier, JSValue value)
 149 {
 150     toObject(exec, exec->lexicalGlobalObject())->put(exec, identifier, value);
 151 }
 152
 153 bool JSCell::deleteProperty(ExecState* exec, const Identifier& identifier)
 154 {
 155     return toObject(exec, exec->lexicalGlobalObject())->deleteProperty(exec, identifier);
 156 }
 157
 158 bool JSCell::deleteProperty(ExecState* exec, unsigned identifier)
 159 {
 160     return toObject(exec, exec->lexicalGlobalObject())->deleteProperty(exec, identifier);
 161 }
 162
 163 JSObject* JSCell::toThisObject(ExecState* exec) const
 164 {
 165     return toObject(exec, exec->lexicalGlobalObject());
 166 }
 167
 168 JSValue JSCell::getJSNumber()
 169 {
 170     return JSValue();
 171 }
 172
 173 bool JSCell::isGetterSetter() const
 174 {
 175     return false;
 176 }
 177
 178 JSValue JSCell::toPrimitive(ExecState*, PreferredPrimitiveType) const
 179 {
 180     ASSERT_NOT_REACHED();
 181     return JSValue();
 182 }
 183
 184 bool JSCell::getPrimitiveNumber(ExecState*, double&, JSValue&)
 185 {
 186     ASSERT_NOT_REACHED();
 187     return false;
 188 }
 189
 190 bool JSCell::toBoolean(ExecState*) const
 191 {
 192     ASSERT_NOT_REACHED();
 193     return false;
 194 }
 195
 196 double JSCell::toNumber(ExecState*) const
 197 {
 198     ASSERT_NOT_REACHED();
 199     return 0;
 200 }
 201
 202 UString JSCell::toString(ExecState*) const
 203 {
 204     ASSERT_NOT_REACHED();
 205     return UString();
 206 }
 207
 208 JSObject* JSCell::toObject(ExecState*, JSGlobalObject*) const
 209 {
 210     ASSERT_NOT_REACHED();
 211     return 0;
 212 }
 213
 214 bool isZombie(const JSCell* cell)
 215 {
 216 #if ENABLE(JSC_ZOMBIES)
 217     return cell && cell->isZombie();
 218 #else
 219     UNUSED_PARAM(cell);
 220     return false;
 221 #endif
 222 }
 223
 224 void slowValidateCell(JSCell* cell)
 225 {
 226     ASSERT_GC_OBJECT_LOOKS_VALID(cell);
 227 }
 228
 229 } // namespace JSC