js/public/Symbol.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 /* Symbols. */
   7
   8 #ifndef js_Symbol_h
   9 #define js_Symbol_h
  10
  11 #include <stddef.h>  // size_t
  12 #include <stdint.h>  // uintptr_t, uint32_t
  13
  14 #include "jstypes.h"  // JS_PUBLIC_API
  15
  16 #include "js/RootingAPI.h"  // JS::Handle
  17
  18 struct JSContext;
  19 class JSString;
  20
  21 namespace JS {
  22
  23 class Symbol;
  24
  25 /**
  26  * Create a new Symbol with the given description. This function never returns
  27  * a Symbol that is in the Runtime-wide symbol registry.
  28  *
  29  * If description is null, the new Symbol's [[Description]] attribute is
  30  * undefined.
  31  */
  32 extern JS_PUBLIC_API Symbol* NewSymbol(JSContext* cx,
  33                                        Handle<JSString*> description);
  34
  35 /**
  36  * Symbol.for as specified in ES6.
  37  *
  38  * Get a Symbol with the description 'key' from the Runtime-wide symbol
  39  * registry. If there is not already a Symbol with that description in the
  40  * registry, a new Symbol is created and registered. 'key' must not be null.
  41  */
  42 extern JS_PUBLIC_API Symbol* GetSymbolFor(JSContext* cx, Handle<JSString*> key);
  43
  44 /**
  45  * Get the [[Description]] attribute of the given symbol.
  46  *
  47  * This function is infallible. If it returns null, that means the symbol's
  48  * [[Description]] is undefined.
  49  */
  50 extern JS_PUBLIC_API JSString* GetSymbolDescription(Handle<Symbol*> symbol);
  51
  52 /* Well-known symbols. */
  53 #define JS_FOR_EACH_WELL_KNOWN_SYMBOL(MACRO) \
  54   MACRO(isConcatSpreadable)                  \
  55   MACRO(iterator)                            \
  56   MACRO(match)                               \
  57   MACRO(replace)                             \
  58   MACRO(search)                              \
  59   MACRO(species)                             \
  60   MACRO(hasInstance)                         \
  61   MACRO(split)                               \
  62   MACRO(toPrimitive)                         \
  63   MACRO(toStringTag)                         \
  64   MACRO(unscopables)                         \
  65   MACRO(asyncIterator)                       \
  66   MACRO(matchAll)
  67
  68 enum class SymbolCode : uint32_t {
  69 // There is one SymbolCode for each well-known symbol.
  70 #define JS_DEFINE_SYMBOL_ENUM(name) name,
  71   JS_FOR_EACH_WELL_KNOWN_SYMBOL(
  72       JS_DEFINE_SYMBOL_ENUM)  // SymbolCode::iterator, etc.
  73 #undef JS_DEFINE_SYMBOL_ENUM
  74   Limit,
  75   WellKnownAPILimit =
  76       0x80000000,  // matches JS::shadow::Symbol::WellKnownAPILimit for inline
  77                    // use
  78   InSymbolRegistry =
  79       0xfffffffe,            // created by Symbol.for() or JS::GetSymbolFor()
  80   UniqueSymbol = 0xffffffff  // created by Symbol() or JS::NewSymbol()
  81 };
  82
  83 /* For use in loops that iterate over the well-known symbols. */
  84 const size_t WellKnownSymbolLimit = size_t(SymbolCode::Limit);
  85
  86 /**
  87  * Return the SymbolCode telling what sort of symbol `symbol` is.
  88  *
  89  * A symbol's SymbolCode never changes once it is created.
  90  */
  91 extern JS_PUBLIC_API SymbolCode GetSymbolCode(Handle<Symbol*> symbol);
  92
  93 /**
  94  * Get one of the well-known symbols defined by ES6. A single set of well-known
  95  * symbols is shared by all compartments in a JSRuntime.
  96  *
  97  * `which` must be in the range [0, WellKnownSymbolLimit).
  98  */
  99 extern JS_PUBLIC_API Symbol* GetWellKnownSymbol(JSContext* cx,
 100                                                 SymbolCode which);
 101
 102 /**
 103  * Return true if the given JSPropertySpec::name or JSFunctionSpec::name value
 104  * is actually a symbol code and not a string. See JS_SYM_FN.
 105  */
 106 inline bool PropertySpecNameIsSymbol(uintptr_t name) {
 107   return name != 0 && name - 1 < WellKnownSymbolLimit;
 108 }
 109
 110 }  // namespace JS
 111
 112 #endif /* js_Symbol_h */