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_ArrayObject_h
8 #define vm_ArrayObject_h
9 
10 #include "vm/NativeObject.h"
11 
12 namespace js {
13 
14 class AutoSetNewObjectMetadata;
15 
16 class ArrayObject : public NativeObject {
17  public:
18   // Array(x) eagerly allocates dense elements if x <= this value. Without
19   // the subtraction the max would roll over to the next power-of-two (4096)
20   // due to the way that growElements() and goodAllocated() work.
21   static const uint32_t EagerAllocationMaxLength =
22       2048 - ObjectElements::VALUES_PER_HEADER;
23 
24   static const JSClass class_;
25 
lengthIsWritable()26   bool lengthIsWritable() const {
27     return !getElementsHeader()->hasNonwritableArrayLength();
28   }
29 
length()30   uint32_t length() const { return getElementsHeader()->length; }
31 
setNonWritableLength(JSContext * cx)32   void setNonWritableLength(JSContext* cx) {
33     shrinkCapacityToInitializedLength(cx);
34     getElementsHeader()->setNonwritableArrayLength();
35   }
36 
37   inline void setLength(JSContext* cx, uint32_t length);
38 
39   // Variant of setLength for use on arrays where the length cannot overflow
40   // int32_t.
setLengthInt32(uint32_t length)41   void setLengthInt32(uint32_t length) {
42     MOZ_ASSERT(lengthIsWritable());
43     MOZ_ASSERT_IF(length != getElementsHeader()->length,
44                   !denseElementsAreFrozen());
45     MOZ_ASSERT(length <= INT32_MAX);
46     getElementsHeader()->length = length;
47   }
48 
49   // Make an array object with the specified initial state.
50   static inline ArrayObject* createArray(JSContext* cx, gc::AllocKind kind,
51                                          gc::InitialHeap heap,
52                                          HandleShape shape,
53                                          HandleObjectGroup group,
54                                          uint32_t length,
55                                          AutoSetNewObjectMetadata& metadata);
56 
57   // Make a copy-on-write array object which shares the elements of an
58   // existing object.
59   static inline ArrayObject* createCopyOnWriteArray(
60       JSContext* cx, gc::InitialHeap heap,
61       HandleArrayObject sharedElementsOwner);
62 
63  private:
64   // Helper for the above methods.
65   static inline ArrayObject* createArrayInternal(
66       JSContext* cx, gc::AllocKind kind, gc::InitialHeap heap,
67       HandleShape shape, HandleObjectGroup group, AutoSetNewObjectMetadata&);
68 
69   static inline ArrayObject* finishCreateArray(
70       ArrayObject* obj, HandleShape shape, AutoSetNewObjectMetadata& metadata);
71 };
72 
73 }  // namespace js
74 
75 #endif  // vm_ArrayObject_h
76