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annotate app/src/main/java/ch/ethz/ssh2/channel/Channel.java @ 438:d29cce60f393
migrate from Eclipse to Android Studio
| author | Carl Byington <carl@five-ten-sg.com> |
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| date | Thu, 03 Dec 2015 11:23:55 -0800 |
| parents | src/ch/ethz/ssh2/channel/Channel.java@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.channel; |
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6 |
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7 import java.io.IOException; |
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8 |
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9 import ch.ethz.ssh2.transport.TransportManager; |
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10 |
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11 /** |
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12 * Channel. |
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13 * |
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14 * @author Christian Plattner |
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15 * @version $Id: Channel.java 123 2014-04-12 21:11:47Z dkocher@sudo.ch $ |
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16 */ |
| 307 | 17 public class Channel { |
| 18 /* | |
| 19 * OK. Here is an important part of the JVM Specification: | |
| 20 * (http://java.sun.com/docs/books/vmspec/2nd-edition/html/Threads.doc.html#22214) | |
| 21 * | |
| 22 * Any association between locks and variables is purely conventional. | |
| 23 * Locking any lock conceptually flushes all variables from a thread's | |
| 24 * working memory, and unlocking any lock forces the writing out to main | |
| 25 * memory of all variables that the thread has assigned. That a lock may be | |
| 26 * associated with a particular object or a class is purely a convention. | |
| 27 * (...) | |
| 28 * | |
| 29 * If a thread uses a particular shared variable only after locking a | |
| 30 * particular lock and before the corresponding unlocking of that same lock, | |
| 31 * then the thread will read the shared value of that variable from main | |
| 32 * memory after the lock operation, if necessary, and will copy back to main | |
| 33 * memory the value most recently assigned to that variable before the | |
| 34 * unlock operation. | |
| 35 * | |
| 36 * This, in conjunction with the mutual exclusion rules for locks, suffices | |
| 37 * to guarantee that values are correctly transmitted from one thread to | |
| 38 * another through shared variables. | |
| 39 * | |
| 40 * ====> Always keep that in mind when modifying the Channel/ChannelManger | |
| 41 * code. | |
| 42 * | |
| 43 */ | |
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44 |
| 307 | 45 public static final int STATE_OPENING = 1; |
| 46 public static final int STATE_OPEN = 2; | |
| 47 public static final int STATE_CLOSED = 4; | |
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48 |
| 307 | 49 static final int CHANNEL_BUFFER_SIZE = 32 * 1024 * 3 * 2; |
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50 |
| 307 | 51 /* |
| 52 * To achieve correctness, the following rules have to be respected when | |
| 53 * accessing this object: | |
| 54 */ | |
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55 |
| 307 | 56 // These fields can always be read |
| 57 final ChannelManager cm; | |
| 58 final ChannelOutputStream stdinStream; | |
| 59 final ChannelInputStream stdoutStream; | |
| 60 final ChannelInputStream stderrStream; | |
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61 |
| 307 | 62 // In case this channel belongs to a server-side session. |
| 63 ServerSessionImpl ss; | |
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64 |
| 307 | 65 // These two fields will only be written while the Channel is in state |
| 66 // STATE_OPENING. | |
| 67 // The code makes sure that the two fields are written out when the state is | |
| 68 // changing to STATE_OPEN. | |
| 69 // Therefore, if you know that the Channel is in state STATE_OPEN, then you | |
| 70 // can read these two fields without synchronizing on the Channel. However, make | |
| 71 // sure that you get the latest values (e.g., flush caches by synchronizing on any | |
| 72 // object). However, to be on the safe side, you can lock the channel. | |
| 73 | |
| 74 int localID = -1; | |
| 75 int remoteID = -1; | |
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76 |
| 307 | 77 /* |
| 78 * Make sure that we never send a data/EOF/WindowChange msg after a CLOSE | |
| 79 * msg. | |
| 80 * | |
| 81 * This is a little bit complicated, but we have to do it in that way, since | |
| 82 * we cannot keep a lock on the Channel during the send operation (this | |
| 83 * would block sometimes the receiver thread, and, in extreme cases, can | |
| 84 * lead to a deadlock on both sides of the connection (senders are blocked | |
| 85 * since the receive buffers on the other side are full, and receiver | |
| 86 * threads wait for the senders to finish). It all depends on the | |
| 87 * implementation on the other side. But we cannot make any assumptions, we | |
| 88 * have to assume the worst case. Confused? Just believe me. | |
| 89 */ | |
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90 |
| 307 | 91 /* |
| 92 * If you send a message on a channel, then you have to aquire the | |
| 93 * "channelSendLock" and check the "closeMessageSent" flag (this variable | |
| 94 * may only be accessed while holding the "channelSendLock" !!! | |
| 95 * | |
| 96 * BTW: NEVER EVER SEND MESSAGES FROM THE RECEIVE THREAD - see explanation | |
| 97 * above. | |
| 98 */ | |
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99 |
| 307 | 100 final Object channelSendLock = new Object(); |
| 101 boolean closeMessageSent = false; | |
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102 |
| 307 | 103 /* |
| 104 * Stop memory fragmentation by allocating this often used buffer. | |
| 105 * May only be used while holding the channelSendLock | |
| 106 */ | |
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107 |
| 307 | 108 final byte[] msgWindowAdjust = new byte[9]; |
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109 |
| 307 | 110 // If you access (read or write) any of the following fields, then you have |
| 111 // to synchronize on the channel. | |
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112 |
| 307 | 113 int state = STATE_OPENING; |
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114 |
| 307 | 115 boolean closeMessageRecv = false; |
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116 |
| 307 | 117 /* This is a stupid implementation. At the moment we can only wait |
| 118 * for one pending request per channel. | |
| 119 */ | |
| 120 int successCounter = 0; | |
| 121 int failedCounter = 0; | |
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122 |
| 307 | 123 int localWindow = 0; /* locally, we use a small window, < 2^31 */ |
| 124 long remoteWindow = 0; /* long for readable 2^32 - 1 window support */ | |
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125 |
| 307 | 126 int localMaxPacketSize = -1; |
| 127 int remoteMaxPacketSize = -1; | |
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128 |
| 307 | 129 final byte[] stdoutBuffer = new byte[CHANNEL_BUFFER_SIZE]; |
| 130 final byte[] stderrBuffer = new byte[CHANNEL_BUFFER_SIZE]; | |
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131 |
| 307 | 132 int stdoutReadpos = 0; |
| 133 int stdoutWritepos = 0; | |
| 134 int stderrReadpos = 0; | |
| 135 int stderrWritepos = 0; | |
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136 |
| 307 | 137 boolean EOF = false; |
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138 |
| 307 | 139 Integer exit_status; |
| 140 | |
| 141 String exit_signal; | |
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142 |
| 307 | 143 // we keep the x11 cookie so that this channel can be closed when this |
| 144 // specific x11 forwarding gets stopped | |
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145 |
| 307 | 146 String hexX11FakeCookie; |
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147 |
| 307 | 148 // reasonClosed is special, since we sometimes need to access it |
| 149 // while holding the channelSendLock. | |
| 150 // We protect it with a private short term lock. | |
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151 |
| 307 | 152 private final Object reasonClosedLock = new Object(); |
| 153 private IOException reasonClosed = null; | |
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154 |
| 307 | 155 public Channel(ChannelManager cm) { |
| 156 this.cm = cm; | |
| 157 this.localWindow = CHANNEL_BUFFER_SIZE; | |
| 158 this.localMaxPacketSize = TransportManager.MAX_PACKET_SIZE; | |
| 159 this.stdinStream = new ChannelOutputStream(this); | |
| 160 this.stdoutStream = new ChannelInputStream(this, false); | |
| 161 this.stderrStream = new ChannelInputStream(this, true); | |
| 162 } | |
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163 |
| 307 | 164 /* Methods to allow access from classes outside of this package */ |
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165 |
| 307 | 166 public ChannelInputStream getStderrStream() { |
| 167 return stderrStream; | |
| 168 } | |
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169 |
| 307 | 170 public ChannelOutputStream getStdinStream() { |
| 171 return stdinStream; | |
| 172 } | |
| 173 | |
| 174 public ChannelInputStream getStdoutStream() { | |
| 175 return stdoutStream; | |
| 176 } | |
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177 |
| 307 | 178 public String getExitSignal() { |
| 179 synchronized (this) { | |
| 180 return exit_signal; | |
| 181 } | |
| 182 } | |
| 183 | |
| 184 public Integer getExitStatus() { | |
| 185 synchronized (this) { | |
| 186 return exit_status; | |
| 187 } | |
| 188 } | |
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189 |
| 307 | 190 public IOException getReasonClosed() { |
| 191 synchronized (reasonClosedLock) { | |
| 192 return reasonClosed; | |
| 193 } | |
| 194 } | |
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195 |
| 307 | 196 public void setReasonClosed(IOException e) { |
| 197 synchronized (reasonClosedLock) { | |
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198 this.reasonClosed = e; |
| 307 | 199 } |
| 200 } | |
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201 |
| 307 | 202 public int getState() { |
| 203 return this.state; | |
| 204 } | |
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205 } |