KickJava.com: Code - Class EDU.oswego.cs.dl.util.concurrent.LayeredSync

Java API By Example, From Geeks To Geeks.

| Browse | Search | Books |

Code - Class EDU.oswego.cs.dl.util.concurrent.LayeredSync

1 /*
2 File: LayeredSync.java
3
4 Originally written by Doug Lea and released into the public domain.
5 This may be used for any purposes whatsoever without acknowledgment.
6 Thanks for the assistance and support of Sun Microsystems Labs,
7 and everyone contributing, testing, and using this code.
8
9 History:
10 Date Who What
11 1Aug1998 dl Create public version
12 */
13
14 package EDU.oswego.cs.dl.util.concurrent;
15
16 /**
17 * A class that can be used to compose Syncs.
18 * A LayeredSync object manages two other Sync objects,
19 * outer and inner. The acquire operation
20 * invokes outer.acquire() followed by inner.acquire(),
21 * but backing out of outer (via release) upon an exception in inner.
22 * The other methods work similarly.
23 * 
24 * LayeredSyncs can be used to compose arbitrary chains
25 * by arranging that either of the managed Syncs be another
26 * LayeredSync.
27 *
28 * [<a HREF="http://gee.cs.oswego.edu/dl/classes/EDU/oswego/cs/dl/util/concurrent/intro.html"> Introduction to this package. </a>]
29 **/
30
31
32 public class LayeredSync implements Sync {
33
34 protected final Sync outer_;
35 protected final Sync inner_;
36
37 /**
38 * Create a LayeredSync managing the given outer and inner Sync
39 * objects
40 **/
41
42 public LayeredSync(Sync outer, Sync inner) {
43 outer_ = outer;
44 inner_ = inner;
45 }
46
47 public void acquire() throws InterruptedException {
48 outer_.acquire();
49 try {
50 inner_.acquire();
51 }
52 catch (InterruptedException ex) {
53 outer_.release();
54 throw ex;
55 }
56 }
57
58 public boolean attempt(long msecs) throws InterruptedException {
59
60 long start = (msecs <= 0)? 0 : System.currentTimeMillis();
61 long waitTime = msecs;
62
63 if (outer_.attempt(waitTime)) {
64 try {
65 if (msecs > 0)
66 waitTime = msecs - (System.currentTimeMillis() - start);
67 if (inner_.attempt(waitTime))
68 return true;
69 else {
70 outer_.release();
71 return false;
72 }
73 }
74 catch (InterruptedException ex) {
75 outer_.release();
76 throw ex;
77 }
78 }
79 else
80 return false;
81 }
82
83 public void release() {
84 inner_.release();
85 outer_.release();
86 }
87
88 }
89
90
91