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annotate src/ch/ethz/ssh2/StreamGobbler.java @ 381:95188bd4badb
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| author | Carl Byington <carl@five-ten-sg.com> |
|---|---|
| date | Wed, 06 Aug 2014 10:38:50 -0700 |
| parents | 071eccdff8ea |
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| rev | line source |
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1 /* |
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2 * Copyright (c) 2006-2011 Christian Plattner. All rights reserved. |
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3 * Please refer to the LICENSE.txt for licensing details. |
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4 */ |
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5 package ch.ethz.ssh2; |
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6 |
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7 import java.io.IOException; |
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8 import java.io.InputStream; |
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9 import java.io.InterruptedIOException; |
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10 |
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11 /** |
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12 * A <code>StreamGobbler</code> is an InputStream that uses an internal worker |
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13 * thread to constantly consume input from another InputStream. It uses a buffer |
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14 * to store the consumed data. The buffer size is automatically adjusted, if needed. |
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15 * <p/> |
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16 * This class is sometimes very convenient - if you wrap a session's STDOUT and STDERR |
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17 * InputStreams with instances of this class, then you don't have to bother about |
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18 * the shared window of STDOUT and STDERR in the low level SSH-2 protocol, |
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19 * since all arriving data will be immediatelly consumed by the worker threads. |
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20 * Also, as a side effect, the streams will be buffered (e.g., single byte |
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21 * read() operations are faster). |
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22 * <p/> |
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23 * Other SSH for Java libraries include this functionality by default in |
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24 * their STDOUT and STDERR InputStream implementations, however, please be aware |
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25 * that this approach has also a downside: |
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26 * <p/> |
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27 * If you do not call the StreamGobbler's <code>read()</code> method often enough |
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28 * and the peer is constantly sending huge amounts of data, then you will sooner or later |
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29 * encounter a low memory situation due to the aggregated data (well, it also depends on the Java heap size). |
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30 * Joe Average will like this class anyway - a paranoid programmer would never use such an approach. |
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31 * <p/> |
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32 * The term "StreamGobbler" was taken from an article called "When Runtime.exec() won't", |
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33 * see http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html. |
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34 * |
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35 * @author Christian Plattner |
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36 * @version 2.50, 03/15/10 |
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37 */ |
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38 |
| 307 | 39 public class StreamGobbler extends InputStream { |
| 40 class GobblerThread extends Thread { | |
| 41 @Override | |
| 42 public void run() { | |
| 43 byte[] buff = new byte[8192]; | |
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44 |
| 307 | 45 while (true) { |
| 46 try { | |
| 47 int avail = is.read(buff); | |
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48 |
| 307 | 49 synchronized (synchronizer) { |
| 50 if (avail <= 0) { | |
| 51 isEOF = true; | |
| 52 synchronizer.notifyAll(); | |
| 53 break; | |
| 54 } | |
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55 |
| 307 | 56 int space_available = buffer.length - write_pos; |
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57 |
| 307 | 58 if (space_available < avail) { |
| 59 /* compact/resize buffer */ | |
| 60 int unread_size = write_pos - read_pos; | |
| 61 int need_space = unread_size + avail; | |
| 62 byte[] new_buffer = buffer; | |
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63 |
| 307 | 64 if (need_space > buffer.length) { |
| 65 int inc = need_space / 3; | |
| 66 inc = (inc < 256) ? 256 : inc; | |
| 67 inc = (inc > 8192) ? 8192 : inc; | |
| 68 new_buffer = new byte[need_space + inc]; | |
| 69 } | |
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70 |
| 307 | 71 if (unread_size > 0) |
| 72 System.arraycopy(buffer, read_pos, new_buffer, 0, unread_size); | |
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73 |
| 307 | 74 buffer = new_buffer; |
| 75 read_pos = 0; | |
| 76 write_pos = unread_size; | |
| 77 } | |
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78 |
| 307 | 79 System.arraycopy(buff, 0, buffer, write_pos, avail); |
| 80 write_pos += avail; | |
| 81 synchronizer.notifyAll(); | |
| 82 } | |
| 83 } | |
| 84 catch (IOException e) { | |
| 85 synchronized (synchronizer) { | |
| 86 exception = e; | |
| 87 synchronizer.notifyAll(); | |
| 88 break; | |
| 89 } | |
| 90 } | |
| 91 } | |
| 92 } | |
| 93 } | |
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94 |
| 307 | 95 private InputStream is; |
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96 |
| 307 | 97 private final Object synchronizer = new Object(); |
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98 |
| 307 | 99 private boolean isEOF = false; |
| 100 private boolean isClosed = false; | |
| 101 private IOException exception = null; | |
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102 |
| 307 | 103 private byte[] buffer = new byte[2048]; |
| 104 private int read_pos = 0; | |
| 105 private int write_pos = 0; | |
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106 |
| 307 | 107 public StreamGobbler(InputStream is) { |
| 108 this.is = is; | |
| 109 GobblerThread t = new GobblerThread(); | |
| 110 t.setDaemon(true); | |
| 111 t.start(); | |
| 112 } | |
| 113 | |
| 114 @Override | |
| 115 public int read() throws IOException { | |
| 116 synchronized (synchronizer) { | |
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117 if (isClosed) |
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118 throw new IOException("This StreamGobbler is closed."); |
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119 |
| 307 | 120 while (read_pos == write_pos) { |
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121 if (exception != null) |
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122 throw exception; |
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123 |
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124 if (isEOF) |
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125 return -1; |
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126 |
| 307 | 127 try { |
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128 synchronizer.wait(); |
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129 } |
| 307 | 130 catch (InterruptedException e) { |
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131 throw new InterruptedIOException(); |
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132 } |
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133 } |
| 307 | 134 |
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135 return buffer[read_pos++] & 0xff; |
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136 } |
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137 } |
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138 |
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139 @Override |
| 307 | 140 public int available() throws IOException { |
| 141 synchronized (synchronizer) { | |
| 142 if (isClosed) | |
| 143 throw new IOException("This StreamGobbler is closed."); | |
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144 |
| 307 | 145 return write_pos - read_pos; |
| 146 } | |
| 147 } | |
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148 |
| 307 | 149 @Override |
| 150 public int read(byte[] b) throws IOException { | |
| 151 return read(b, 0, b.length); | |
| 152 } | |
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153 |
| 307 | 154 @Override |
| 155 public void close() throws IOException { | |
| 156 synchronized (synchronizer) { | |
| 157 if (isClosed) | |
| 158 return; | |
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159 |
| 307 | 160 isClosed = true; |
| 161 isEOF = true; | |
| 162 synchronizer.notifyAll(); | |
| 163 is.close(); | |
| 164 } | |
| 165 } | |
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166 |
| 307 | 167 @Override |
| 168 public int read(byte[] b, int off, int len) throws IOException { | |
| 169 if (b == null) | |
| 170 throw new NullPointerException(); | |
| 171 | |
| 172 if ((off < 0) || (len < 0) || ((off + len) > b.length) || ((off + len) < 0) || (off > b.length)) | |
| 173 throw new IndexOutOfBoundsException(); | |
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174 |
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175 if (len == 0) |
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176 return 0; |
| 307 | 177 |
| 178 synchronized (synchronizer) { | |
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179 if (isClosed) |
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180 throw new IOException("This StreamGobbler is closed."); |
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181 |
| 307 | 182 while (read_pos == write_pos) { |
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183 if (exception != null) |
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184 throw exception; |
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185 |
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186 if (isEOF) |
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187 return -1; |
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188 |
| 307 | 189 try { |
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190 synchronizer.wait(); |
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191 } |
| 307 | 192 catch (InterruptedException e) { |
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193 throw new InterruptedIOException(); |
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194 } |
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195 } |
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196 |
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197 int avail = write_pos - read_pos; |
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198 avail = (avail > len) ? len : avail; |
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199 System.arraycopy(buffer, read_pos, b, off, avail); |
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200 read_pos += avail; |
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201 return avail; |
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202 } |
| 307 | 203 } |
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204 } |