1 /*
2 * Copyright (C) 2013 Google 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 are
6 * met:
7 *
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above
11 * copyright notice, this list of conditions and the following disclaimer
12 * in the documentation and/or other materials provided with the
13 * distribution.
14 * * Neither the name of Google Inc. nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31 #include "config.h"
32 #include "wtf/ArrayBufferBuilder.h"
33
34 #include "wtf/Assertions.h"
35 #include <limits>
36
37 namespace WTF {
38
39 static const int defaultBufferCapacity = 32768;
40
ArrayBufferBuilder()41 ArrayBufferBuilder::ArrayBufferBuilder()
42 : m_bytesUsed(0)
43 , m_variableCapacity(true)
44 {
45 m_buffer = ArrayBuffer::create(defaultBufferCapacity, 1);
46 }
47
expandCapacity(unsigned sizeToIncrease)48 bool ArrayBufferBuilder::expandCapacity(unsigned sizeToIncrease)
49 {
50 unsigned currentBufferSize = m_buffer->byteLength();
51
52 // If the size of the buffer exceeds max of unsigned, it can't be grown any
53 // more.
54 if (sizeToIncrease > std::numeric_limits<unsigned>::max() - m_bytesUsed)
55 return false;
56
57 unsigned newBufferSize = m_bytesUsed + sizeToIncrease;
58
59 // Grow exponentially if possible.
60 unsigned exponentialGrowthNewBufferSize = std::numeric_limits<unsigned>::max();
61 if (currentBufferSize <= std::numeric_limits<unsigned>::max() / 2)
62 exponentialGrowthNewBufferSize = currentBufferSize * 2;
63 if (exponentialGrowthNewBufferSize > newBufferSize)
64 newBufferSize = exponentialGrowthNewBufferSize;
65
66 // Copy existing data in current buffer to new buffer.
67 RefPtr<ArrayBuffer> newBuffer = ArrayBuffer::create(newBufferSize, 1);
68 if (!newBuffer)
69 return false;
70
71 memcpy(newBuffer->data(), m_buffer->data(), m_bytesUsed);
72 m_buffer = newBuffer;
73 return true;
74 }
75
append(const char * data,unsigned length)76 unsigned ArrayBufferBuilder::append(const char* data, unsigned length)
77 {
78 ASSERT(length > 0);
79
80 unsigned currentBufferSize = m_buffer->byteLength();
81
82 ASSERT(m_bytesUsed <= currentBufferSize);
83
84 unsigned remainingBufferSpace = currentBufferSize - m_bytesUsed;
85
86 unsigned bytesToSave = length;
87
88 if (length > remainingBufferSpace) {
89 if (m_variableCapacity) {
90 if (!expandCapacity(length))
91 return 0;
92 } else {
93 bytesToSave = remainingBufferSpace;
94 }
95 }
96
97 memcpy(static_cast<char*>(m_buffer->data()) + m_bytesUsed, data, bytesToSave);
98 m_bytesUsed += bytesToSave;
99
100 return bytesToSave;
101 }
102
toArrayBuffer()103 PassRefPtr<ArrayBuffer> ArrayBufferBuilder::toArrayBuffer()
104 {
105 // Fully used. Return m_buffer as-is.
106 if (m_buffer->byteLength() == m_bytesUsed)
107 return m_buffer;
108
109 return m_buffer->slice(0, m_bytesUsed);
110 }
111
toString()112 String ArrayBufferBuilder::toString()
113 {
114 return String(static_cast<const char*>(m_buffer->data()), m_bytesUsed);
115 }
116
shrinkToFit()117 void ArrayBufferBuilder::shrinkToFit()
118 {
119 ASSERT(m_bytesUsed <= m_buffer->byteLength());
120
121 if (m_buffer->byteLength() > m_bytesUsed)
122 m_buffer = m_buffer->slice(0, m_bytesUsed);
123 }
124
125 } // namespace WTF
126