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2 package com.trilead.ssh2.util;
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3
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4 import java.io.PrintWriter;
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5 import java.io.StringWriter;
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6 import java.util.Collections;
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7 import java.util.LinkedList;
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8
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9 import com.trilead.ssh2.log.Logger;
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10
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11
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12 /**
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13 * TimeoutService (beta). Here you can register a timeout.
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14 * <p>
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15 * Implemented having large scale programs in mind: if you open many concurrent SSH connections
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16 * that rely on timeouts, then there will be only one timeout thread. Once all timeouts
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17 * have expired/are cancelled, the thread will (sooner or later) exit.
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18 * Only after new timeouts arrive a new thread (singleton) will be instantiated.
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19 *
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20 * @author Christian Plattner, plattner@trilead.com
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21 * @version $Id: TimeoutService.java,v 1.1 2007/10/15 12:49:57 cplattne Exp $
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22 */
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23 public class TimeoutService {
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24 private static final Logger log = Logger.getLogger(TimeoutService.class);
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25
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26 public static class TimeoutToken implements Comparable {
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27 private long runTime;
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28 private Runnable handler;
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29
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30 private TimeoutToken(long runTime, Runnable handler) {
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31 this.runTime = runTime;
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32 this.handler = handler;
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33 }
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34
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35 public int compareTo(Object o) {
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36 TimeoutToken t = (TimeoutToken) o;
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37
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38 if (runTime > t.runTime)
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39 return 1;
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40
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41 if (runTime == t.runTime)
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42 return 0;
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43
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44 return -1;
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45 }
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46 }
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47
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48 private static class TimeoutThread extends Thread {
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49 public void run() {
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50 synchronized (todolist) {
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51 while (true) {
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52 if (todolist.size() == 0) {
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53 timeoutThread = null;
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54 return;
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55 }
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56
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57 long now = System.currentTimeMillis();
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58 TimeoutToken tt = (TimeoutToken) todolist.getFirst();
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59
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60 if (tt.runTime > now) {
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61 /* Not ready yet, sleep a little bit */
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62 try {
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63 todolist.wait(tt.runTime - now);
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64 }
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65 catch (InterruptedException e) {
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66 }
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67
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68 /* We cannot simply go on, since it could be that the token
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69 * was removed (cancelled) or another one has been inserted in
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70 * the meantime.
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71 */
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72 continue;
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73 }
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74
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75 todolist.removeFirst();
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76
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77 try {
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78 tt.handler.run();
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79 }
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80 catch (Exception e) {
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81 StringWriter sw = new StringWriter();
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82 e.printStackTrace(new PrintWriter(sw));
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83 log.log(20, "Exeception in Timeout handler:" + e.getMessage() + "(" + sw.toString() + ")");
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84 }
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85 }
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86 }
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87 }
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88 }
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89
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90 /* The list object is also used for locking purposes */
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91 private static final LinkedList todolist = new LinkedList();
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92
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93 private static Thread timeoutThread = null;
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94
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95 /**
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96 * It is assumed that the passed handler will not execute for a long time.
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97 *
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98 * @param runTime
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99 * @param handler
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100 * @return a TimeoutToken that can be used to cancel the timeout.
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101 */
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102 public static final TimeoutToken addTimeoutHandler(long runTime, Runnable handler) {
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103 TimeoutToken token = new TimeoutToken(runTime, handler);
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104
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105 synchronized (todolist) {
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106 todolist.add(token);
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107 Collections.sort(todolist);
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108
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109 if (timeoutThread != null)
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110 timeoutThread.interrupt();
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111 else {
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112 timeoutThread = new TimeoutThread();
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113 timeoutThread.setDaemon(true);
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114 timeoutThread.start();
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115 }
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116 }
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117
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118 return token;
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119 }
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120
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121 public static final void cancelTimeoutHandler(TimeoutToken token) {
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122 synchronized (todolist) {
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123 todolist.remove(token);
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124
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125 if (timeoutThread != null)
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126 timeoutThread.interrupt();
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127 }
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128 }
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129
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130 }
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