third_party/WebKit/Source/wtf/ArrayBufferBuilder.cpp

   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
  41 ArrayBufferBuilder::ArrayBufferBuilder()
  42     : m_bytesUsed(0)
  43     , m_variableCapacity(true)
  44 {
  45     m_buffer = ArrayBuffer::create(defaultBufferCapacity, 1);
  46 }
  47
  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
  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
 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
 112 String ArrayBufferBuilder::toString()
 113 {
 114     return String(static_cast<const char*>(m_buffer->data()), m_bytesUsed);
 115 }
 116
 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