1/*
2 * Copyright (C) 2012, 2014 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef IndexingHeader_h
27#define IndexingHeader_h
28
29#include "PropertyStorage.h"
30
31namespace JSC {
32
33class ArrayBuffer;
34class Butterfly;
35class LLIntOffsetsExtractor;
36class Structure;
37struct ArrayStorage;
38
39class IndexingHeader {
40public:
41 // Define the maximum storage vector length to be 2^32 / sizeof(JSValue) / 2 to ensure that
42 // there is no risk of overflow.
43 enum { maximumLength = 0x10000000 };
44
45 static ptrdiff_t offsetOfIndexingHeader() { return -static_cast<ptrdiff_t>(sizeof(IndexingHeader)); }
46
47 static ptrdiff_t offsetOfArrayBuffer() { return OBJECT_OFFSETOF(IndexingHeader, u.typedArray.buffer); }
48 static ptrdiff_t offsetOfPublicLength() { return OBJECT_OFFSETOF(IndexingHeader, u.lengths.publicLength); }
49 static ptrdiff_t offsetOfVectorLength() { return OBJECT_OFFSETOF(IndexingHeader, u.lengths.vectorLength); }
50
51 IndexingHeader()
52 {
53 u.lengths.publicLength = 0;
54 u.lengths.vectorLength = 0;
55 }
56
57 uint32_t vectorLength() const { return u.lengths.vectorLength; }
58
59 void setVectorLength(uint32_t length)
60 {
61 RELEASE_ASSERT(length <= maximumLength);
62 u.lengths.vectorLength = length;
63 }
64
65 uint32_t publicLength() const { return u.lengths.publicLength; }
66 void setPublicLength(uint32_t auxWord) { u.lengths.publicLength = auxWord; }
67
68 ArrayBuffer* arrayBuffer() { return u.typedArray.buffer; }
69 void setArrayBuffer(ArrayBuffer* buffer) { u.typedArray.buffer = buffer; }
70
71 static IndexingHeader* from(Butterfly* butterfly)
72 {
73 return reinterpret_cast<IndexingHeader*>(butterfly) - 1;
74 }
75
76 static const IndexingHeader* from(const Butterfly* butterfly)
77 {
78 return reinterpret_cast<const IndexingHeader*>(butterfly) - 1;
79 }
80
81 static IndexingHeader* from(ArrayStorage* arrayStorage)
82 {
83 return const_cast<IndexingHeader*>(from(const_cast<const ArrayStorage*>(arrayStorage)));
84 }
85
86 static const IndexingHeader* from(const ArrayStorage* arrayStorage)
87 {
88 return reinterpret_cast<const IndexingHeader*>(arrayStorage) - 1;
89 }
90
91 static IndexingHeader* fromEndOf(PropertyStorage propertyStorage)
92 {
93 return reinterpret_cast<IndexingHeader*>(propertyStorage);
94 }
95
96 PropertyStorage propertyStorage()
97 {
98 return reinterpret_cast_ptr<PropertyStorage>(this);
99 }
100
101 ConstPropertyStorage propertyStorage() const
102 {
103 return reinterpret_cast_ptr<ConstPropertyStorage>(this);
104 }
105
106 ArrayStorage* arrayStorage()
107 {
108 return reinterpret_cast<ArrayStorage*>(this + 1);
109 }
110
111 Butterfly* butterfly()
112 {
113 return reinterpret_cast<Butterfly*>(this + 1);
114 }
115
116 // These methods are not standalone in the sense that they cannot be
117 // used on a copy of the IndexingHeader.
118 size_t preCapacity(Structure*);
119 size_t indexingPayloadSizeInBytes(Structure*);
120
121private:
122 friend class LLIntOffsetsExtractor;
123
124 union {
125 struct {
126 uint32_t publicLength; // The meaning of this field depends on the array type, but for all JSArrays we rely on this being the publicly visible length (array.length).
127 uint32_t vectorLength; // The length of the indexed property storage. The actual size of the storage depends on this, and the type.
128 } lengths;
129
130 struct {
131 ArrayBuffer* buffer;
132 } typedArray;
133 } u;
134};
135
136} // namespace JSC
137
138#endif // IndexingHeader_h
139
140