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/Shape.h"
12 
13 namespace js {
14 
15 class StringObject : public NativeObject {
16   static const unsigned PRIMITIVE_VALUE_SLOT = 0;
17   static const unsigned LENGTH_SLOT = 1;
18 
19   static const ClassSpec classSpec_;
20 
21  public:
22   static const unsigned RESERVED_SLOTS = 2;
23 
24   static const JSClass class_;
25 
26   /*
27    * Creates a new String object boxing the given string.  The object's
28    * [[Prototype]] is determined from context.
29    */
30   static inline StringObject* create(JSContext* cx, HandleString str,
31                                      HandleObject proto = nullptr,
32                                      NewObjectKind newKind = GenericObject);
33 
34   /*
35    * Compute the initial shape to associate with fresh String objects, which
36    * encodes the initial length property. Return the shape after changing
37    * |obj|'s last property to it.
38    */
39   static Shape* assignInitialShape(JSContext* cx, Handle<StringObject*> obj);
40 
unbox()41   JSString* unbox() const {
42     return getFixedSlot(PRIMITIVE_VALUE_SLOT).toString();
43   }
44 
length()45   inline size_t length() const {
46     return size_t(getFixedSlot(LENGTH_SLOT).toInt32());
47   }
48 
offsetOfPrimitiveValue()49   static size_t offsetOfPrimitiveValue() {
50     return getFixedSlotOffset(PRIMITIVE_VALUE_SLOT);
51   }
offsetOfLength()52   static size_t offsetOfLength() { return getFixedSlotOffset(LENGTH_SLOT); }
53 
54  private:
55   static inline bool init(JSContext* cx, Handle<StringObject*> obj,
56                           HandleString str);
57 
58   static JSObject* createPrototype(JSContext* cx, JSProtoKey key);
59 
setStringThis(JSString * str)60   void setStringThis(JSString* str) {
61     MOZ_ASSERT(getReservedSlot(PRIMITIVE_VALUE_SLOT).isUndefined());
62     setFixedSlot(PRIMITIVE_VALUE_SLOT, StringValue(str));
63     setFixedSlot(LENGTH_SLOT, Int32Value(int32_t(str->length())));
64   }
65 };
66 
67 }  // namespace js
68 
69 #endif /* vm_StringObject_h */
70