bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/guarded/GuardedAsyncMultiProcedure.java

   1 /*******************************************************************************
   2  * Copyright (c) 2007, 2010 Association for Decentralized Information Management
   3  * in Industry THTH ry.
   4  * All rights reserved. This program and the accompanying materials
   5  * are made available under the terms of the Eclipse Public License v1.0
   6  * which accompanies this distribution, and is available at
   7  * http://www.eclipse.org/legal/epl-v10.html
   8  *
   9  * Contributors:
  10  *     VTT Technical Research Centre of Finland - initial API and implementation
  11  *******************************************************************************/
  12 package org.simantics.db.common.procedure.guarded;
  13
  14 import java.util.concurrent.atomic.AtomicBoolean;
  15 import java.util.concurrent.atomic.AtomicInteger;
  16
  17 import org.simantics.db.AsyncReadGraph;
  18 import org.simantics.db.common.procedure.adapter.AsyncProcedureSupport;
  19 import org.simantics.db.procedure.AsyncMultiProcedure;
  20
  21 abstract public class GuardedAsyncMultiProcedure<T> implements AsyncMultiProcedure<T>, AsyncProcedureSupport {
  22
  23     private final AsyncMultiProcedure<T> procedure;
  24     private final AtomicBoolean     onceGuard = new AtomicBoolean(false);
  25     private final AtomicInteger     resultCounter;
  26
  27     public GuardedAsyncMultiProcedure(AsyncMultiProcedure<T> procedure) {
  28         this.procedure = procedure;
  29         this.resultCounter = new AtomicInteger(1);
  30     }
  31
  32     @Override
  33     final public void exception(AsyncReadGraph graph, Throwable t) {
  34         except(graph, t);
  35     }
  36
  37     protected void except(AsyncReadGraph graph, Throwable t) {
  38         if (onceGuard.compareAndSet(false, true)) {
  39             procedure.exception(graph, t);
  40         }
  41     }
  42
  43     protected void offer(AsyncReadGraph graph, T item) {
  44         if (!onceGuard.get()) {
  45                 procedure.execute(graph, item);
  46         }
  47     }
  48
  49     protected void dec(AsyncReadGraph graph) {
  50         if (resultCounter.decrementAndGet() <= 0) {
  51             if (onceGuard.compareAndSet(false, true)) {
  52                 procedure.finished(graph);
  53             }
  54         }
  55     }
  56
  57     protected void inc() {
  58         resultCounter.incrementAndGet();
  59     }
  60
  61         @Override
  62         final public void finished(AsyncReadGraph graph) {
  63                 dec(graph);
  64         }
  65
  66 }