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