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
37namespace WTF {
38
39static const int defaultBufferCapacity = 32768;
40
41ArrayBufferBuilder::ArrayBufferBuilder()
42    : m_bytesUsed(0)
43    , m_variableCapacity(true)
44{
45    m_buffer = ArrayBuffer::create(defaultBufferCapacity, 1);
46}
47
48bool 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
76unsigned 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
103PassRefPtr<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
112String ArrayBufferBuilder::toString()
113{
114    return String(static_cast<const char*>(m_buffer->data()), m_bytesUsed);
115}
116
117void 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