runtime/JSValue.h

   1 /*
   2  *  Copyright (C) 1999-2001 Harri Porten (porten@kde.org)
   3  *  Copyright (C) 2001 Peter Kelly (pmk@post.com)
   4  *  Copyright (C) 2003, 2004, 2005, 2007, 2008, 2009 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 #ifndef JSValue_h
  24 #define JSValue_h
  25
  26 #include <math.h>
  27 #include <stddef.h> // for size_t
  28 #include <stdint.h>
  29 #include <wtf/AlwaysInline.h>
  30 #include <wtf/Assertions.h>
  31 #include <wtf/HashMap.h>
  32 #include <wtf/HashTraits.h>
  33 #include <wtf/MathExtras.h>
  34 #include <wtf/StdLibExtras.h>
  35
  36 namespace JSC {
  37
  38     class ExecState;
  39     class Identifier;
  40     class JSCell;
  41     class JSGlobalData;
  42     class JSGlobalObject;
  43     class JSObject;
  44     class JSString;
  45     class PropertySlot;
  46     class PutPropertySlot;
  47     class UString;
  48 #if ENABLE(DFG_JIT)
  49     namespace DFG {
  50         class AssemblyHelpers;
  51         class JITCompiler;
  52         class JITCodeGenerator;
  53         class JSValueSource;
  54         class OSRExitCompiler;
  55         class SpeculativeJIT;
  56     }
  57 #endif
  58     namespace LLInt {
  59         class Data;
  60     }
  61
  62     struct ClassInfo;
  63     struct Instruction;
  64     struct MethodTable;
  65
  66     template <class T> class WriteBarrierBase;
  67
  68     enum PreferredPrimitiveType { NoPreference, PreferNumber, PreferString };
  69
  70
  71 #if USE(JSVALUE32_64)
  72     typedef int64_t EncodedJSValue;
  73 #else
  74     typedef void* EncodedJSValue;
  75 #endif
  76
  77     union EncodedValueDescriptor {
  78         int64_t asInt64;
  79 #if USE(JSVALUE32_64)
  80         double asDouble;
  81 #elif USE(JSVALUE64)
  82         JSCell* ptr;
  83 #endif
  84
  85 #if CPU(BIG_ENDIAN)
  86         struct {
  87             int32_t tag;
  88             int32_t payload;
  89         } asBits;
  90 #else
  91         struct {
  92             int32_t payload;
  93             int32_t tag;
  94         } asBits;
  95 #endif
  96     };
  97
  98     // This implements ToInt32, defined in ECMA-262 9.5.
  99     JS_EXPORT_PRIVATE int32_t toInt32(double);
 100
 101     // This implements ToUInt32, defined in ECMA-262 9.6.
 102     inline uint32_t toUInt32(double number)
 103     {
 104         // As commented in the spec, the operation of ToInt32 and ToUint32 only differ
 105         // in how the result is interpreted; see NOTEs in sections 9.5 and 9.6.
 106         return toInt32(number);
 107     }
 108
 109     class JSValue {
 110         friend struct EncodedJSValueHashTraits;
 111         friend class JIT;
 112         friend class JITStubs;
 113         friend class JITStubCall;
 114         friend class JSInterfaceJIT;
 115         friend class SpecializedThunkJIT;
 116 #if ENABLE(DFG_JIT)
 117         friend class DFG::AssemblyHelpers;
 118         friend class DFG::JITCompiler;
 119         friend class DFG::JITCodeGenerator;
 120         friend class DFG::JSValueSource;
 121         friend class DFG::OSRExitCompiler;
 122         friend class DFG::SpeculativeJIT;
 123 #endif
 124         friend class LLInt::Data;
 125
 126     public:
 127         static EncodedJSValue encode(JSValue);
 128         static JSValue decode(EncodedJSValue);
 129
 130         enum JSNullTag { JSNull };
 131         enum JSUndefinedTag { JSUndefined };
 132         enum JSTrueTag { JSTrue };
 133         enum JSFalseTag { JSFalse };
 134         enum EncodeAsDoubleTag { EncodeAsDouble };
 135
 136         JSValue();
 137         JSValue(JSNullTag);
 138         JSValue(JSUndefinedTag);
 139         JSValue(JSTrueTag);
 140         JSValue(JSFalseTag);
 141         JSValue(JSCell* ptr);
 142         JSValue(const JSCell* ptr);
 143
 144         // Numbers
 145         JSValue(EncodeAsDoubleTag, double);
 146         explicit JSValue(double);
 147         explicit JSValue(char);
 148         explicit JSValue(unsigned char);
 149         explicit JSValue(short);
 150         explicit JSValue(unsigned short);
 151         explicit JSValue(int);
 152         explicit JSValue(unsigned);
 153         explicit JSValue(long);
 154         explicit JSValue(unsigned long);
 155         explicit JSValue(long long);
 156         explicit JSValue(unsigned long long);
 157
 158         operator bool() const;
 159         bool operator==(const JSValue& other) const;
 160         bool operator!=(const JSValue& other) const;
 161
 162         bool isInt32() const;
 163         bool isUInt32() const;
 164         bool isDouble() const;
 165         bool isTrue() const;
 166         bool isFalse() const;
 167
 168         int32_t asInt32() const;
 169         uint32_t asUInt32() const;
 170         double asDouble() const;
 171         bool asBoolean() const;
 172         double asNumber() const;
 173
 174         // Querying the type.
 175         bool isEmpty() const;
 176         bool isFunction() const;
 177         bool isUndefined() const;
 178         bool isNull() const;
 179         bool isUndefinedOrNull() const;
 180         bool isBoolean() const;
 181         bool isNumber() const;
 182         bool isString() const;
 183         bool isPrimitive() const;
 184         bool isGetterSetter() const;
 185         bool isObject() const;
 186         bool inherits(const ClassInfo*) const;
 187
 188         // Extracting the value.
 189         bool getString(ExecState* exec, UString&) const;
 190         UString getString(ExecState* exec) const; // null string if not a string
 191         JSObject* getObject() const; // 0 if not an object
 192
 193         // Extracting integer values.
 194         bool getUInt32(uint32_t&) const;
 195
 196         // Basic conversions.
 197         JSValue toPrimitive(ExecState*, PreferredPrimitiveType = NoPreference) const;
 198         bool getPrimitiveNumber(ExecState*, double& number, JSValue&);
 199
 200         bool toBoolean(ExecState*) const;
 201
 202         // toNumber conversion is expected to be side effect free if an exception has
 203         // been set in the ExecState already.
 204         double toNumber(ExecState*) const;
 205         JSString* toString(ExecState*) const;
 206         UString toUString(ExecState*) const;
 207         UString toUStringInline(ExecState*) const;
 208         JSObject* toObject(ExecState*) const;
 209         JSObject* toObject(ExecState*, JSGlobalObject*) const;
 210
 211         // Integer conversions.
 212         JS_EXPORT_PRIVATE double toInteger(ExecState*) const;
 213         double toIntegerPreserveNaN(ExecState*) const;
 214         int32_t toInt32(ExecState*) const;
 215         uint32_t toUInt32(ExecState*) const;
 216
 217         // Floating point conversions (this is a convenience method for webcore;
 218         // signle precision float is not a representation used in JS or JSC).
 219         float toFloat(ExecState* exec) const { return static_cast<float>(toNumber(exec)); }
 220
 221         // Object operations, with the toObject operation included.
 222         JSValue get(ExecState*, const Identifier& propertyName) const;
 223         JSValue get(ExecState*, const Identifier& propertyName, PropertySlot&) const;
 224         JSValue get(ExecState*, unsigned propertyName) const;
 225         JSValue get(ExecState*, unsigned propertyName, PropertySlot&) const;
 226         void put(ExecState*, const Identifier& propertyName, JSValue, PutPropertySlot&);
 227         void putToPrimitive(ExecState*, const Identifier& propertyName, JSValue, PutPropertySlot&);
 228         void putByIndex(ExecState*, unsigned propertyName, JSValue, bool shouldThrow);
 229
 230         JSObject* toThisObject(ExecState*) const;
 231
 232         static bool equal(ExecState* exec, JSValue v1, JSValue v2);
 233         static bool equalSlowCase(ExecState* exec, JSValue v1, JSValue v2);
 234         static bool equalSlowCaseInline(ExecState* exec, JSValue v1, JSValue v2);
 235         static bool strictEqual(ExecState* exec, JSValue v1, JSValue v2);
 236         static bool strictEqualSlowCase(ExecState* exec, JSValue v1, JSValue v2);
 237         static bool strictEqualSlowCaseInline(ExecState* exec, JSValue v1, JSValue v2);
 238
 239         bool isCell() const;
 240         JSCell* asCell() const;
 241         JS_EXPORT_PRIVATE bool isValidCallee();
 242
 243         char* description();
 244
 245         JS_EXPORT_PRIVATE JSObject* synthesizePrototype(ExecState*) const;
 246
 247     private:
 248         template <class T> JSValue(WriteBarrierBase<T>);
 249
 250         enum HashTableDeletedValueTag { HashTableDeletedValue };
 251         JSValue(HashTableDeletedValueTag);
 252
 253         inline const JSValue asValue() const { return *this; }
 254         JS_EXPORT_PRIVATE double toNumberSlowCase(ExecState*) const;
 255         JS_EXPORT_PRIVATE JSString* toStringSlowCase(ExecState*) const;
 256         JS_EXPORT_PRIVATE UString toUStringSlowCase(ExecState*) const;
 257         JS_EXPORT_PRIVATE JSObject* toObjectSlowCase(ExecState*, JSGlobalObject*) const;
 258         JS_EXPORT_PRIVATE JSObject* toThisObjectSlowCase(ExecState*) const;
 259
 260 #if USE(JSVALUE32_64)
 261         /*
 262          * On 32-bit platforms USE(JSVALUE32_64) should be defined, and we use a NaN-encoded
 263          * form for immediates.
 264          *
 265          * The encoding makes use of unused NaN space in the IEEE754 representation.  Any value
 266          * with the top 13 bits set represents a QNaN (with the sign bit set).  QNaN values
 267          * can encode a 51-bit payload.  Hardware produced and C-library payloads typically
 268          * have a payload of zero.  We assume that non-zero payloads are available to encode
 269          * pointer and integer values.  Since any 64-bit bit pattern where the top 15 bits are
 270          * all set represents a NaN with a non-zero payload, we can use this space in the NaN
 271          * ranges to encode other values (however there are also other ranges of NaN space that
 272          * could have been selected).
 273          *
 274          * For JSValues that do not contain a double value, the high 32 bits contain the tag
 275          * values listed in the enums below, which all correspond to NaN-space. In the case of
 276          * cell, integer and bool values the lower 32 bits (the 'payload') contain the pointer
 277          * integer or boolean value; in the case of all other tags the payload is 0.
 278          */
 279         enum { Int32Tag =        0xffffffff };
 280         enum { BooleanTag =      0xfffffffe };
 281         enum { NullTag =         0xfffffffd };
 282         enum { UndefinedTag =    0xfffffffc };
 283         enum { CellTag =         0xfffffffb };
 284         enum { EmptyValueTag =   0xfffffffa };
 285         enum { DeletedValueTag = 0xfffffff9 };
 286
 287         enum { LowestTag =  DeletedValueTag };
 288
 289         uint32_t tag() const;
 290         int32_t payload() const;
 291 #elif USE(JSVALUE64)
 292         /*
 293          * On 64-bit platforms USE(JSVALUE64) should be defined, and we use a NaN-encoded
 294          * form for immediates.
 295          *
 296          * The encoding makes use of unused NaN space in the IEEE754 representation.  Any value
 297          * with the top 13 bits set represents a QNaN (with the sign bit set).  QNaN values
 298          * can encode a 51-bit payload.  Hardware produced and C-library payloads typically
 299          * have a payload of zero.  We assume that non-zero payloads are available to encode
 300          * pointer and integer values.  Since any 64-bit bit pattern where the top 15 bits are
 301          * all set represents a NaN with a non-zero payload, we can use this space in the NaN
 302          * ranges to encode other values (however there are also other ranges of NaN space that
 303          * could have been selected).
 304          *
 305          * This range of NaN space is represented by 64-bit numbers begining with the 16-bit
 306          * hex patterns 0xFFFE and 0xFFFF - we rely on the fact that no valid double-precision
 307          * numbers will begin fall in these ranges.
 308          *
 309          * The top 16-bits denote the type of the encoded JSValue:
 310          *
 311          *     Pointer {  0000:PPPP:PPPP:PPPP
 312          *              / 0001:****:****:****
 313          *     Double  {         ...
 314          *              \ FFFE:****:****:****
 315          *     Integer {  FFFF:0000:IIII:IIII
 316          *
 317          * The scheme we have implemented encodes double precision values by performing a
 318          * 64-bit integer addition of the value 2^48 to the number. After this manipulation
 319          * no encoded double-precision value will begin with the pattern 0x0000 or 0xFFFF.
 320          * Values must be decoded by reversing this operation before subsequent floating point
 321          * operations my be peformed.
 322          *
 323          * 32-bit signed integers are marked with the 16-bit tag 0xFFFF.
 324          *
 325          * The tag 0x0000 denotes a pointer, or another form of tagged immediate. Boolean,
 326          * null and undefined values are represented by specific, invalid pointer values:
 327          *
 328          *     False:     0x06
 329          *     True:      0x07
 330          *     Undefined: 0x0a
 331          *     Null:      0x02
 332          *
 333          * These values have the following properties:
 334          * - Bit 1 (TagBitTypeOther) is set for all four values, allowing real pointers to be
 335          *   quickly distinguished from all immediate values, including these invalid pointers.
 336          * - With bit 3 is masked out (TagBitUndefined) Undefined and Null share the
 337          *   same value, allowing null & undefined to be quickly detected.
 338          *
 339          * No valid JSValue will have the bit pattern 0x0, this is used to represent array
 340          * holes, and as a C++ 'no value' result (e.g. JSValue() has an internal value of 0).
 341          */
 342
 343         // These values are #defines since using static const integers here is a ~1% regression!
 344
 345         // This value is 2^48, used to encode doubles such that the encoded value will begin
 346         // with a 16-bit pattern within the range 0x0001..0xFFFE.
 347         #define DoubleEncodeOffset 0x1000000000000ll
 348         // If all bits in the mask are set, this indicates an integer number,
 349         // if any but not all are set this value is a double precision number.
 350         #define TagTypeNumber 0xffff000000000000ll
 351
 352         // All non-numeric (bool, null, undefined) immediates have bit 2 set.
 353         #define TagBitTypeOther 0x2ll
 354         #define TagBitBool      0x4ll
 355         #define TagBitUndefined 0x8ll
 356         // Combined integer value for non-numeric immediates.
 357         #define ValueFalse     (TagBitTypeOther | TagBitBool | false)
 358         #define ValueTrue      (TagBitTypeOther | TagBitBool | true)
 359         #define ValueUndefined (TagBitTypeOther | TagBitUndefined)
 360         #define ValueNull      (TagBitTypeOther)
 361
 362         // TagMask is used to check for all types of immediate values (either number or 'other').
 363         #define TagMask (TagTypeNumber | TagBitTypeOther)
 364
 365         // These special values are never visible to JavaScript code; Empty is used to represent
 366         // Array holes, and for uninitialized JSValues. Deleted is used in hash table code.
 367         // These values would map to cell types in the JSValue encoding, but not valid GC cell
 368         // pointer should have either of these values (Empty is null, deleted is at an invalid
 369         // alignment for a GC cell, and in the zero page).
 370         #define ValueEmpty   0x0ll
 371         #define ValueDeleted 0x4ll
 372 #endif
 373
 374         EncodedValueDescriptor u;
 375     };
 376
 377 #if USE(JSVALUE32_64)
 378     typedef IntHash<EncodedJSValue> EncodedJSValueHash;
 379
 380     struct EncodedJSValueHashTraits : HashTraits<EncodedJSValue> {
 381         static const bool emptyValueIsZero = false;
 382         static EncodedJSValue emptyValue() { return JSValue::encode(JSValue()); }
 383         static void constructDeletedValue(EncodedJSValue& slot) { slot = JSValue::encode(JSValue(JSValue::HashTableDeletedValue)); }
 384         static bool isDeletedValue(EncodedJSValue value) { return value == JSValue::encode(JSValue(JSValue::HashTableDeletedValue)); }
 385     };
 386 #else
 387     typedef PtrHash<EncodedJSValue> EncodedJSValueHash;
 388
 389     struct EncodedJSValueHashTraits : HashTraits<EncodedJSValue> {
 390         static void constructDeletedValue(EncodedJSValue& slot) { slot = JSValue::encode(JSValue(JSValue::HashTableDeletedValue)); }
 391         static bool isDeletedValue(EncodedJSValue value) { return value == JSValue::encode(JSValue(JSValue::HashTableDeletedValue)); }
 392     };
 393 #endif
 394
 395     typedef HashMap<EncodedJSValue, unsigned, EncodedJSValueHash, EncodedJSValueHashTraits> JSValueMap;
 396
 397     // Stand-alone helper functions.
 398     inline JSValue jsNull()
 399     {
 400         return JSValue(JSValue::JSNull);
 401     }
 402
 403     inline JSValue jsUndefined()
 404     {
 405         return JSValue(JSValue::JSUndefined);
 406     }
 407
 408     inline JSValue jsBoolean(bool b)
 409     {
 410         return b ? JSValue(JSValue::JSTrue) : JSValue(JSValue::JSFalse);
 411     }
 412
 413     ALWAYS_INLINE JSValue jsDoubleNumber(double d)
 414     {
 415         ASSERT(JSValue(JSValue::EncodeAsDouble, d).isNumber());
 416         return JSValue(JSValue::EncodeAsDouble, d);
 417     }
 418
 419     ALWAYS_INLINE JSValue jsNumber(double d)
 420     {
 421         ASSERT(JSValue(d).isNumber());
 422         return JSValue(d);
 423     }
 424
 425     ALWAYS_INLINE JSValue jsNumber(char i)
 426     {
 427         return JSValue(i);
 428     }
 429
 430     ALWAYS_INLINE JSValue jsNumber(unsigned char i)
 431     {
 432         return JSValue(i);
 433     }
 434
 435     ALWAYS_INLINE JSValue jsNumber(short i)
 436     {
 437         return JSValue(i);
 438     }
 439
 440     ALWAYS_INLINE JSValue jsNumber(unsigned short i)
 441     {
 442         return JSValue(i);
 443     }
 444
 445     ALWAYS_INLINE JSValue jsNumber(int i)
 446     {
 447         return JSValue(i);
 448     }
 449
 450     ALWAYS_INLINE JSValue jsNumber(unsigned i)
 451     {
 452         return JSValue(i);
 453     }
 454
 455     ALWAYS_INLINE JSValue jsNumber(long i)
 456     {
 457         return JSValue(i);
 458     }
 459
 460     ALWAYS_INLINE JSValue jsNumber(unsigned long i)
 461     {
 462         return JSValue(i);
 463     }
 464
 465     ALWAYS_INLINE JSValue jsNumber(long long i)
 466     {
 467         return JSValue(i);
 468     }
 469
 470     ALWAYS_INLINE JSValue jsNumber(unsigned long long i)
 471     {
 472         return JSValue(i);
 473     }
 474
 475     inline bool operator==(const JSValue a, const JSCell* b) { return a == JSValue(b); }
 476     inline bool operator==(const JSCell* a, const JSValue b) { return JSValue(a) == b; }
 477
 478     inline bool operator!=(const JSValue a, const JSCell* b) { return a != JSValue(b); }
 479     inline bool operator!=(const JSCell* a, const JSValue b) { return JSValue(a) != b; }
 480
 481 } // namespace JSC
 482
 483 #endif // JSValue_h