Semaphore


1   /*******************************************************************************
2    * Copyright (c) 2000, 2006 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    *
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   *******************************************************************************/
11  package org.eclipse.ui.internal;
12  
13  public class Semaphore {
14      protected long notifications;
15  
16      protected Thread   operation;
17  
18      protected Runnable   runnable;
19  
20      public Semaphore(Runnable   runnable) {
21          this.runnable = runnable;
22          notifications = 0;
23      }
24  
25      /**
26       * Attempts to acquire this semaphore.  Returns true if it was successfully acquired,
27       * and false otherwise.
28       */
29      public synchronized boolean acquire(long delay) throws InterruptedException   {
30          if (Thread.interrupted()) {
31              throw new InterruptedException  ();
32          }
33          long start = System.currentTimeMillis();
34          long timeLeft = delay;
35          while (true) {
36              if (notifications > 0) {
37                  notifications--;
38                  return true;
39              }
40              if (timeLeft <= 0) {
41                  return false;
42              }
43              wait(timeLeft);
44              timeLeft = start + delay - System.currentTimeMillis();
45          }
46      }
47  
48      public boolean equals(Object   obj) {
49          return (runnable == ((Semaphore) obj).runnable);
50      }
51  
52      public Thread   getOperationThread() {
53          return operation;
54      }
55  
56      public Runnable   getRunnable() {
57          return runnable;
58      }
59  
60      public int hashCode() {
61          return runnable == null ? 0 : runnable.hashCode();
62      }
63  
64      public synchronized void release() {
65          notifications++;
66          notifyAll();
67      }
68  
69      public void setOperationThread(Thread   operation) {
70          this.operation = operation;
71      }
72  
73      // for debug only
74      public String   toString() {
75          return "Semaphore(" + runnable + ")"; //$NON-NLS-1$ //$NON-NLS-2$
76      }
77  }
78
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