• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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/Vector.h>
31 
32 namespace WTF {
33 
34 template <typename T> class BlockStack {
35 public:
36     static const size_t blockSize = 4096;
37     static const size_t blockLength = blockSize / sizeof(T);
38 
39     BlockStack();
40     ~BlockStack();
41 
42     T* grow();
43     void shrink(T*);
44 
45     const Vector<T*>& blocks();
46 
47 private:
48     Vector<T*> m_blocks;
49     T* m_spareBlock; // Used to avoid thrash at block boundaries.
50 };
51 
BlockStack()52 template <typename T> BlockStack<T>::BlockStack()
53     : m_spareBlock(0)
54 {
55 }
56 
~BlockStack()57 template <typename T> BlockStack<T>::~BlockStack()
58 {
59     if (m_spareBlock)
60         free(m_spareBlock);
61     for (size_t i = 0; i < m_blocks.size(); ++i)
62         free(m_blocks[i]);
63 }
64 
blocks()65 template <typename T> inline const Vector<T*>& BlockStack<T>::blocks()
66 {
67     return m_blocks;
68 }
69 
grow()70 template <typename T> T* BlockStack<T>::grow()
71 {
72     T* block = m_spareBlock ? m_spareBlock : static_cast<T*>(malloc(blockSize));
73     m_spareBlock = 0;
74 
75     m_blocks.append(block);
76     return block;
77 }
78 
shrink(T * newEnd)79 template <typename T> void BlockStack<T>::shrink(T* newEnd)
80 {
81     ASSERT(newEnd != m_blocks.last() + blockLength);
82     m_spareBlock = m_blocks.last();
83     m_blocks.removeLast();
84 
85     while (m_blocks.last() + blockLength != newEnd) {
86         free(m_blocks.last());
87         m_blocks.removeLast();
88     }
89 }
90 
91 }
92 
93 using WTF::BlockStack;
94 
95 #endif
96