bundles/org.simantics.acorn/src/org/simantics/acorn/lru/ClusterUpdateState.java

   1 package org.simantics.acorn.lru;
   2
   3 import java.util.concurrent.Semaphore;
   4
   5 import org.simantics.db.service.ClusterUID;
   6
   7 public class ClusterUpdateState {
   8
   9         final ClusterUID uid;
  10         final Semaphore lock = new Semaphore(0);
  11         int referenceCount = 0;
  12         boolean inUpdate = false;
  13
  14         ClusterUpdateState(ClusterUID uid) {
  15                 this.uid = uid;
  16         }
  17
  18         public void waitForUpdates() {
  19                 try {
  20                         lock.acquire();
  21                 } catch (InterruptedException e) {
  22                         e.printStackTrace();
  23                 }
  24         }
  25
  26         public synchronized void beginUpdate() {
  27 //          System.err.println("ClusterUpdateState.beginUpdate() for " + uid + ", inUpdate=" + inUpdate);
  28                 assert(!inUpdate);
  29                 inUpdate = true;
  30         }
  31
  32         public synchronized void endUpdate() {
  33 //          System.err.println("ClusterUpdateState.endUpdate() for " + uid + ", inUpdate=" + inUpdate);
  34                 assert(inUpdate);
  35                 inUpdate = false;
  36         }
  37
  38         public synchronized void incRef() {
  39                 referenceCount++;
  40         }
  41
  42         public synchronized ClusterUpdateState decRef() {
  43                 referenceCount--;
  44                 if(referenceCount == 0) {
  45                         lock.release(Integer.MAX_VALUE);
  46                         return null;
  47                 }
  48                 return this;
  49         }
  50
  51 }