js/src/vm/StringObject.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef vm_StringObject_h
   8 #define vm_StringObject_h
   9
  10 #include "vm/JSObject.h"
  11 #include "vm/NativeObject.h"
  12
  13 namespace js {
  14
  15 class Shape;
  16
  17 class StringObject : public NativeObject {
  18   static const unsigned PRIMITIVE_VALUE_SLOT = 0;
  19   static const unsigned LENGTH_SLOT = 1;
  20
  21   static const ClassSpec classSpec_;
  22
  23  public:
  24   static const unsigned RESERVED_SLOTS = 2;
  25
  26   static const JSClass class_;
  27
  28   /*
  29    * Creates a new String object boxing the given string.  The object's
  30    * [[Prototype]] is determined from context.
  31    */
  32   static inline StringObject* create(JSContext* cx, HandleString str,
  33                                      HandleObject proto = nullptr,
  34                                      NewObjectKind newKind = GenericObject);
  35
  36   /*
  37    * Compute the initial shape to associate with fresh String objects, which
  38    * encodes the initial length property. Return the shape after changing
  39    * |obj|'s last property to it.
  40    */
  41   static SharedShape* assignInitialShape(JSContext* cx,
  42                                          Handle<StringObject*> obj);
  43
  44   JSString* unbox() const {
  45     return getFixedSlot(PRIMITIVE_VALUE_SLOT).toString();
  46   }
  47
  48   inline size_t length() const {
  49     return size_t(getFixedSlot(LENGTH_SLOT).toInt32());
  50   }
  51
  52   static size_t offsetOfPrimitiveValue() {
  53     return getFixedSlotOffset(PRIMITIVE_VALUE_SLOT);
  54   }
  55   static size_t offsetOfLength() { return getFixedSlotOffset(LENGTH_SLOT); }
  56
  57  private:
  58   static inline bool init(JSContext* cx, Handle<StringObject*> obj,
  59                           HandleString str);
  60
  61   static JSObject* createPrototype(JSContext* cx, JSProtoKey key);
  62
  63   void setStringThis(JSString* str) {
  64     MOZ_ASSERT(getReservedSlot(PRIMITIVE_VALUE_SLOT).isUndefined());
  65     setFixedSlot(PRIMITIVE_VALUE_SLOT, StringValue(str));
  66     setFixedSlot(LENGTH_SLOT, Int32Value(int32_t(str->length())));
  67   }
  68 };
  69
  70 }  // namespace js
  71
  72 #endif /* vm_StringObject_h */