1 | /** |
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2 | * Licensed to the Apache Software Foundation (ASF) under one |
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3 | * or more contributor license agreements. See the NOTICE file |
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4 | * distributed with this work for additional information |
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5 | * regarding copyright ownership. The ASF licenses this file |
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6 | * to you under the Apache License, Version 2.0 (the |
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7 | * "License"); you may not use this file except in compliance |
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8 | * with the License. You may obtain a copy of the License at |
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9 | * |
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10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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11 | * |
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12 | * Unless required by applicable law or agreed to in writing, software |
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13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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15 | * See the License for the specific language governing permissions and |
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16 | * limitations under the License. |
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17 | */ |
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18 | |
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19 | package org.apache.hadoop.fs; |
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20 | |
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21 | import java.io.IOException; |
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22 | import java.io.OutputStream; |
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23 | import java.util.zip.Checksum; |
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24 | |
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25 | /** |
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26 | * This is a generic output stream for generating checksums for |
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27 | * data before it is written to the underlying stream |
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28 | */ |
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29 | |
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30 | abstract public class FSOutputSummer extends OutputStream { |
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31 | // data checksum |
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32 | private Checksum sum; |
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33 | // internal buffer for storing data before it is checksumed |
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34 | private byte buf[]; |
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35 | // internal buffer for storing checksum |
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36 | private byte checksum[]; |
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37 | // The number of valid bytes in the buffer. |
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38 | private int count; |
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39 | |
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40 | protected FSOutputSummer(Checksum sum, int maxChunkSize, int checksumSize) { |
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41 | this.sum = sum; |
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42 | this.buf = new byte[maxChunkSize]; |
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43 | this.checksum = new byte[checksumSize]; |
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44 | this.count = 0; |
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45 | } |
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46 | |
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47 | /* write the data chunk in <code>b</code> staring at <code>offset</code> with |
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48 | * a length of <code>len</code>, and its checksum |
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49 | */ |
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50 | protected abstract void writeChunk(byte[] b, int offset, int len, byte[] checksum) |
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51 | throws IOException; |
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52 | |
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53 | /** Write one byte */ |
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54 | public synchronized void write(int b) throws IOException { |
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55 | sum.update(b); |
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56 | buf[count++] = (byte)b; |
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57 | if(count == buf.length) { |
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58 | flushBuffer(); |
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59 | } |
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60 | } |
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61 | |
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62 | /** |
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63 | * Writes <code>len</code> bytes from the specified byte array |
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64 | * starting at offset <code>off</code> and generate a checksum for |
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65 | * each data chunk. |
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66 | * |
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67 | * <p> This method stores bytes from the given array into this |
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68 | * stream's buffer before it gets checksumed. The buffer gets checksumed |
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69 | * and flushed to the underlying output stream when all data |
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70 | * in a checksum chunk are in the buffer. If the buffer is empty and |
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71 | * requested length is at least as large as the size of next checksum chunk |
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72 | * size, this method will checksum and write the chunk directly |
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73 | * to the underlying output stream. Thus it avoids uneccessary data copy. |
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74 | * |
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75 | * @param b the data. |
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76 | * @param off the start offset in the data. |
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77 | * @param len the number of bytes to write. |
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78 | * @exception IOException if an I/O error occurs. |
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79 | */ |
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80 | public synchronized void write(byte b[], int off, int len) |
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81 | throws IOException { |
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82 | if (off < 0 || len < 0 || off > b.length - len) { |
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83 | throw new ArrayIndexOutOfBoundsException(); |
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84 | } |
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85 | |
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86 | for (int n=0;n<len;n+=write1(b, off+n, len-n)) { |
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87 | } |
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88 | } |
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89 | |
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90 | /** |
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91 | * Write a portion of an array, flushing to the underlying |
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92 | * stream at most once if necessary. |
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93 | */ |
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94 | private int write1(byte b[], int off, int len) throws IOException { |
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95 | if(count==0 && len>=buf.length) { |
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96 | // local buffer is empty and user data has one chunk |
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97 | // checksum and output data |
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98 | final int length = buf.length; |
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99 | sum.update(b, off, length); |
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100 | writeChecksumChunk(b, off, length, false); |
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101 | return length; |
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102 | } |
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103 | |
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104 | // copy user data to local buffer |
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105 | int bytesToCopy = buf.length-count; |
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106 | bytesToCopy = (len<bytesToCopy) ? len : bytesToCopy; |
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107 | sum.update(b, off, bytesToCopy); |
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108 | System.arraycopy(b, off, buf, count, bytesToCopy); |
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109 | count += bytesToCopy; |
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110 | if (count == buf.length) { |
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111 | // local buffer is full |
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112 | flushBuffer(); |
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113 | } |
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114 | return bytesToCopy; |
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115 | } |
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116 | |
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117 | /* Forces any buffered output bytes to be checksumed and written out to |
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118 | * the underlying output stream. |
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119 | */ |
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120 | protected synchronized void flushBuffer() throws IOException { |
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121 | flushBuffer(false); |
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122 | } |
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123 | |
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124 | /* Forces any buffered output bytes to be checksumed and written out to |
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125 | * the underlying output stream. If keep is true, then the state of |
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126 | * this object remains intact. |
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127 | */ |
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128 | protected synchronized void flushBuffer(boolean keep) throws IOException { |
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129 | if (count != 0) { |
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130 | int chunkLen = count; |
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131 | count = 0; |
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132 | writeChecksumChunk(buf, 0, chunkLen, keep); |
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133 | if (keep) { |
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134 | count = chunkLen; |
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135 | } |
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136 | } |
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137 | } |
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138 | |
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139 | /** Generate checksum for the data chunk and output data chunk & checksum |
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140 | * to the underlying output stream. If keep is true then keep the |
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141 | * current checksum intact, do not reset it. |
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142 | */ |
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143 | private void writeChecksumChunk(byte b[], int off, int len, boolean keep) |
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144 | throws IOException { |
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145 | int tempChecksum = (int)sum.getValue(); |
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146 | if (!keep) { |
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147 | sum.reset(); |
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148 | } |
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149 | int2byte(tempChecksum, checksum); |
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150 | writeChunk(b, off, len, checksum); |
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151 | } |
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152 | |
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153 | /** |
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154 | * Converts a checksum integer value to a byte stream |
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155 | */ |
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156 | static public byte[] convertToByteStream(Checksum sum, int checksumSize) { |
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157 | return int2byte((int)sum.getValue(), new byte[checksumSize]); |
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158 | } |
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159 | |
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160 | static byte[] int2byte(int integer, byte[] bytes) { |
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161 | bytes[0] = (byte)((integer >>> 24) & 0xFF); |
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162 | bytes[1] = (byte)((integer >>> 16) & 0xFF); |
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163 | bytes[2] = (byte)((integer >>> 8) & 0xFF); |
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164 | bytes[3] = (byte)((integer >>> 0) & 0xFF); |
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165 | return bytes; |
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166 | } |
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167 | |
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168 | /** |
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169 | * Resets existing buffer with a new one of the specified size. |
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170 | */ |
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171 | protected synchronized void resetChecksumChunk(int size) { |
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172 | sum.reset(); |
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173 | this.buf = new byte[size]; |
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174 | this.count = 0; |
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175 | } |
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176 | } |
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