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      1 /*
      2  *  Copyright (C) 1999-2001 Harri Porten (porten (at) kde.org)
      3  *  Copyright (C) 2001 Peter Kelly (pmk (at) 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 bool JSCell::getUInt32(uint32_t&) const
     80 {
     81     return false;
     82 }
     83 
     84 bool JSCell::getString(ExecState* exec, UString&stringValue) const
     85 {
     86     if (!isString())
     87         return false;
     88     stringValue = static_cast<const JSString*>(this)->value(exec);
     89     return true;
     90 }
     91 
     92 UString JSCell::getString(ExecState* exec) const
     93 {
     94     return isString() ? static_cast<const JSString*>(this)->value(exec) : UString();
     95 }
     96 
     97 JSObject* JSCell::getObject()
     98 {
     99     return isObject() ? asObject(this) : 0;
    100 }
    101 
    102 const JSObject* JSCell::getObject() const
    103 {
    104     return isObject() ? static_cast<const JSObject*>(this) : 0;
    105 }
    106 
    107 CallType JSCell::getCallData(CallData&)
    108 {
    109     return CallTypeNone;
    110 }
    111 
    112 ConstructType JSCell::getConstructData(ConstructData&)
    113 {
    114     return ConstructTypeNone;
    115 }
    116 
    117 bool JSCell::getOwnPropertySlot(ExecState* exec, const Identifier& identifier, PropertySlot& slot)
    118 {
    119     // This is not a general purpose implementation of getOwnPropertySlot.
    120     // It should only be called by JSValue::get.
    121     // It calls getPropertySlot, not getOwnPropertySlot.
    122     JSObject* object = toObject(exec, exec->lexicalGlobalObject());
    123     slot.setBase(object);
    124     if (!object->getPropertySlot(exec, identifier, slot))
    125         slot.setUndefined();
    126     return true;
    127 }
    128 
    129 bool JSCell::getOwnPropertySlot(ExecState* exec, unsigned identifier, PropertySlot& slot)
    130 {
    131     // This is not a general purpose implementation of getOwnPropertySlot.
    132     // It should only be called by JSValue::get.
    133     // It calls getPropertySlot, not getOwnPropertySlot.
    134     JSObject* object = toObject(exec, exec->lexicalGlobalObject());
    135     slot.setBase(object);
    136     if (!object->getPropertySlot(exec, identifier, slot))
    137         slot.setUndefined();
    138     return true;
    139 }
    140 
    141 void JSCell::put(ExecState* exec, const Identifier& identifier, JSValue value, PutPropertySlot& slot)
    142 {
    143     toObject(exec, exec->lexicalGlobalObject())->put(exec, identifier, value, slot);
    144 }
    145 
    146 void JSCell::put(ExecState* exec, unsigned identifier, JSValue value)
    147 {
    148     toObject(exec, exec->lexicalGlobalObject())->put(exec, identifier, value);
    149 }
    150 
    151 bool JSCell::deleteProperty(ExecState* exec, const Identifier& identifier)
    152 {
    153     return toObject(exec, exec->lexicalGlobalObject())->deleteProperty(exec, identifier);
    154 }
    155 
    156 bool JSCell::deleteProperty(ExecState* exec, unsigned identifier)
    157 {
    158     return toObject(exec, exec->lexicalGlobalObject())->deleteProperty(exec, identifier);
    159 }
    160 
    161 JSObject* JSCell::toThisObject(ExecState* exec) const
    162 {
    163     return toObject(exec, exec->lexicalGlobalObject());
    164 }
    165 
    166 JSValue JSCell::getJSNumber()
    167 {
    168     return JSValue();
    169 }
    170 
    171 bool JSCell::isGetterSetter() const
    172 {
    173     return false;
    174 }
    175 
    176 JSValue JSCell::toPrimitive(ExecState*, PreferredPrimitiveType) const
    177 {
    178     ASSERT_NOT_REACHED();
    179     return JSValue();
    180 }
    181 
    182 bool JSCell::getPrimitiveNumber(ExecState*, double&, JSValue&)
    183 {
    184     ASSERT_NOT_REACHED();
    185     return false;
    186 }
    187 
    188 bool JSCell::toBoolean(ExecState*) const
    189 {
    190     ASSERT_NOT_REACHED();
    191     return false;
    192 }
    193 
    194 double JSCell::toNumber(ExecState*) const
    195 {
    196     ASSERT_NOT_REACHED();
    197     return 0;
    198 }
    199 
    200 UString JSCell::toString(ExecState*) const
    201 {
    202     ASSERT_NOT_REACHED();
    203     return UString();
    204 }
    205 
    206 JSObject* JSCell::toObject(ExecState*, JSGlobalObject*) const
    207 {
    208     ASSERT_NOT_REACHED();
    209     return 0;
    210 }
    211 
    212 bool isZombie(const JSCell* cell)
    213 {
    214 #if ENABLE(JSC_ZOMBIES)
    215     return cell && cell->isZombie();
    216 #else
    217     UNUSED_PARAM(cell);
    218     return false;
    219 #endif
    220 }
    221 
    222 } // namespace JSC
    223