Mercurial > hg > blitz_stable

annotate src/EDU/oswego/cs/dl/util/concurrent/LayeredSync.java @ 27:511648fa4d64 Version 2.1

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Version to 2.1
author Dan Creswell <dan.creswell@gmail.com>
date Mon, 04 Jan 2010 13:00:40 +0000
parents 3dc0c5604566
children
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1 /*
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2 File: LayeredSync.java
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3
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4 Originally written by Doug Lea and released into the public domain.
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5 This may be used for any purposes whatsoever without acknowledgment.
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6 Thanks for the assistance and support of Sun Microsystems Labs,
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7 and everyone contributing, testing, and using this code.
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8
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9 History:
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10 Date Who What
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11 1Aug1998 dl Create public version
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12 */
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13
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14 package EDU.oswego.cs.dl.util.concurrent;
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15
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16 /**
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17 * A class that can be used to compose Syncs.
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18 * A LayeredSync object manages two other Sync objects,
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19 * <em>outer</em> and <em>inner</em>. The acquire operation
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20 * invokes <em>outer</em>.acquire() followed by <em>inner</em>.acquire(),
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21 * but backing out of outer (via release) upon an exception in inner.
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22 * The other methods work similarly.
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23 * <p>
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24 * LayeredSyncs can be used to compose arbitrary chains
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25 * by arranging that either of the managed Syncs be another
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26 * LayeredSync.
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27 *
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28 * <p>[<a href="http://gee.cs.oswego.edu/dl/classes/EDU/oswego/cs/dl/util/concurrent/intro.html"> Introduction to this package. </a>]
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29 **/
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30
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31
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32 public class LayeredSync implements Sync {
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33
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34 protected final Sync outer_;
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35 protected final Sync inner_;
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36
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37 /**
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38 * Create a LayeredSync managing the given outer and inner Sync
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39 * objects
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40 **/
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41
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42 public LayeredSync(Sync outer, Sync inner) {
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43 outer_ = outer;
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44 inner_ = inner;
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45 }
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46
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47 public void acquire() throws InterruptedException {
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48 outer_.acquire();
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49 try {
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50 inner_.acquire();
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51 }
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52 catch (InterruptedException ex) {
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53 outer_.release();
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54 throw ex;
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55 }
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56 }
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57
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58 public boolean attempt(long msecs) throws InterruptedException {
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59
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60 long start = (msecs <= 0)? 0 : System.currentTimeMillis();
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61 long waitTime = msecs;
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62
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63 if (outer_.attempt(waitTime)) {
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64 try {
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65 if (msecs > 0)
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66 waitTime = msecs - (System.currentTimeMillis() - start);
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67 if (inner_.attempt(waitTime))
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68 return true;
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69 else {
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70 outer_.release();
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71 return false;
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72 }
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73 }
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74 catch (InterruptedException ex) {
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75 outer_.release();
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76 throw ex;
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77 }
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78 }
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79 else
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80 return false;
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81 }
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82
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83 public void release() {
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84 inner_.release();
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85 outer_.release();
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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