1/*
2 * Copyright (C) 2011 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. AND ITS CONTRIBUTORS ``AS IS''
14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23 * THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef BlockStack_h
27#define BlockStack_h
28
29#include <wtf/Assertions.h>
30#include <wtf/FastMalloc.h>
31#include <wtf/Vector.h>
32
33namespace WTF {
34
35template <typename T> class BlockStack {
36public:
37    static const size_t blockSize = 4096;
38    static const size_t blockLength = blockSize / sizeof(T);
39
40    BlockStack();
41    ~BlockStack();
42
43    T* grow();
44    void shrink(T*);
45
46    const Vector<T*>& blocks();
47
48private:
49    Vector<T*> m_blocks;
50    T* m_spareBlock; // Used to avoid thrash at block boundaries.
51};
52
53template <typename T> BlockStack<T>::BlockStack()
54    : m_spareBlock(0)
55{
56}
57
58template <typename T> BlockStack<T>::~BlockStack()
59{
60    if (m_spareBlock)
61        fastFree(m_spareBlock);
62    for (size_t i = 0; i < m_blocks.size(); ++i)
63        fastFree(m_blocks[i]);
64}
65
66template <typename T> inline const Vector<T*>& BlockStack<T>::blocks()
67{
68    return m_blocks;
69}
70
71template <typename T> T* BlockStack<T>::grow()
72{
73    T* block = m_spareBlock ? m_spareBlock : static_cast<T*>(fastMalloc(blockSize));
74    m_spareBlock = 0;
75
76    m_blocks.append(block);
77    return block;
78}
79
80template <typename T> void BlockStack<T>::shrink(T* newEnd)
81{
82    ASSERT(newEnd != m_blocks.last() + blockLength);
83    m_spareBlock = m_blocks.last();
84    m_blocks.removeLast();
85
86    while (m_blocks.last() + blockLength != newEnd) {
87        fastFree(m_blocks.last());
88        m_blocks.removeLast();
89    }
90}
91
92}
93
94using WTF::BlockStack;
95
96#endif
97