Sharing org.simantics.acorn for everyone to use

[simantics/platform.git] / bundles / org.simantics.acorn / src / org / simantics / acorn / lru / ClusterUpdateState.java

diff --git a/bundles/org.simantics.acorn/src/org/simantics/acorn/lru/ClusterUpdateState.java b/bundles/org.simantics.acorn/src/org/simantics/acorn/lru/ClusterUpdateState.java
new file mode 100644 (file)
index 0000000..5ce4688
--- /dev/null
+++ b/bundles/org.simantics.acorn/src/org/simantics/acorn/lru/ClusterUpdateState.java
@@ -0,0 +1,51 @@
+package org.simantics.acorn.lru;
+
+import java.util.concurrent.Semaphore;
+
+import org.simantics.db.service.ClusterUID;
+
+public class ClusterUpdateState {
+       
+       final ClusterUID uid;
+       final Semaphore lock = new Semaphore(0);
+       int referenceCount = 0;
+       boolean inUpdate = false;
+       
+       ClusterUpdateState(ClusterUID uid) {
+               this.uid = uid;
+       }
+       
+       public void waitForUpdates() {
+               try {
+                       lock.acquire();
+               } catch (InterruptedException e) {
+                       e.printStackTrace();
+               }
+       }
+       
+       public synchronized void beginUpdate() {
+//         System.err.println("ClusterUpdateState.beginUpdate() for " + uid + ", inUpdate=" + inUpdate);
+               assert(!inUpdate);
+               inUpdate = true;
+       }
+       
+       public synchronized void endUpdate() {
+//         System.err.println("ClusterUpdateState.endUpdate() for " + uid + ", inUpdate=" + inUpdate);
+               assert(inUpdate);
+               inUpdate = false;
+       }
+       
+       public synchronized void incRef() {
+               referenceCount++;
+       }
+       
+       public synchronized ClusterUpdateState decRef() {
+               referenceCount--;
+               if(referenceCount == 0) {
+                       lock.release(Integer.MAX_VALUE);
+                       return null;
+               }
+               return this;
+       }
+       
+}
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