1/*
2 * Copyright (C) 2012 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 ArrayStorage_h
27#define ArrayStorage_h
28
29#include "ArrayConventions.h"
30#include "Butterfly.h"
31#include "IndexingHeader.h"
32#include "SparseArrayValueMap.h"
33#include "WriteBarrier.h"
34#include <wtf/Noncopyable.h>
35
36namespace JSC {
37
38// This struct holds the actual data values of an array. A JSArray object points to its contained ArrayStorage
39// struct by pointing to m_vector. To access the contained ArrayStorage struct, use the getStorage() and
40// setStorage() methods. It is important to note that there may be space before the ArrayStorage that
41// is used to quick unshift / shift operation. The actual allocated pointer is available by using:
42//     getStorage() - m_indexBias * sizeof(JSValue)
43// All slots in ArrayStorage (slots from 0 to vectorLength) are expected to be initialized to a JSValue or,
44// for hole slots, JSValue().
45struct ArrayStorage {
46    WTF_MAKE_NONCOPYABLE(ArrayStorage);
47private:
48    ArrayStorage() { } // Not directly instantiable. Can only be created as part of a Butterfly.
49public:
50
51    static ArrayStorage* from(Butterfly* butterfly) { return reinterpret_cast_ptr<ArrayStorage*>(butterfly); }
52    static ArrayStorage* from(IndexingHeader* indexingHeader) { return indexingHeader->arrayStorage(); }
53
54    Butterfly* butterfly() { return reinterpret_cast<Butterfly*>(this); }
55    IndexingHeader* indexingHeader() { return IndexingHeader::from(this); }
56    const IndexingHeader* indexingHeader() const { return IndexingHeader::from(this); }
57
58    // We steal two fields from the indexing header: vectorLength and length.
59    unsigned length() const { return indexingHeader()->publicLength(); }
60    void setLength(unsigned length) { indexingHeader()->setPublicLength(length); }
61    unsigned vectorLength() { return indexingHeader()->vectorLength(); }
62    void setVectorLength(unsigned length) { indexingHeader()->setVectorLength(length); }
63
64    ALWAYS_INLINE void copyHeaderFromDuringGC(const ArrayStorage& other)
65    {
66        m_sparseMap.copyFrom(other.m_sparseMap);
67        m_indexBias = other.m_indexBias;
68        m_numValuesInVector = other.m_numValuesInVector;
69    }
70
71    bool hasHoles() const
72    {
73        return m_numValuesInVector != length();
74    }
75
76    bool inSparseMode()
77    {
78        return m_sparseMap && m_sparseMap->sparseMode();
79    }
80
81    ContiguousJSValues vector() { return ContiguousJSValues(m_vector, vectorLength()); }
82
83    WriteBarrier<SparseArrayValueMap> m_sparseMap;
84    unsigned m_indexBias;
85    unsigned m_numValuesInVector;
86#if USE(JSVALUE32_64)
87    uintptr_t m_padding;
88#endif
89    WriteBarrier<Unknown> m_vector[1];
90
91    static ptrdiff_t lengthOffset() { return Butterfly::offsetOfPublicLength(); }
92    static ptrdiff_t vectorLengthOffset() { return Butterfly::offsetOfVectorLength(); }
93    static ptrdiff_t numValuesInVectorOffset() { return OBJECT_OFFSETOF(ArrayStorage, m_numValuesInVector); }
94    static ptrdiff_t vectorOffset() { return OBJECT_OFFSETOF(ArrayStorage, m_vector); }
95    static ptrdiff_t indexBiasOffset() { return OBJECT_OFFSETOF(ArrayStorage, m_indexBias); }
96    static ptrdiff_t sparseMapOffset() { return OBJECT_OFFSETOF(ArrayStorage, m_sparseMap); }
97
98    static size_t sizeFor(unsigned vectorLength)
99    {
100        return ArrayStorage::vectorOffset() + vectorLength * sizeof(WriteBarrier<Unknown>);
101    }
102};
103
104} // namespace JSC
105
106#endif // ArrayStorage_h
107
108