bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/single/wrapper/DeepSingleOrNullProcedure.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.single.wrapper;
  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.utils.Logger;
  19 import org.simantics.db.procedure.AsyncProcedure;
  20
  21 final public class DeepSingleOrNullProcedure<Result> {
  22
  23         private Result result = null;
  24         final AsyncProcedure<Result> procedure;
  25     final AtomicBoolean done = new AtomicBoolean(false);
  26     final AtomicBoolean found = new AtomicBoolean(false);
  27     final AtomicInteger ready = new AtomicInteger(1);
  28
  29     public DeepSingleOrNullProcedure(AsyncProcedure<Result> procedure) {
  30
  31         this.procedure = procedure;
  32
  33     }
  34
  35     public void inc() {
  36
  37         ready.incrementAndGet();
  38
  39     }
  40
  41     public void dec(AsyncReadGraph graph) {
  42
  43         if(ready.decrementAndGet() == 0) {
  44                         // Shall fire exactly once!
  45             if(done.compareAndSet(false, true)) {
  46                 try {
  47                         if(found.compareAndSet(false, true)) {
  48                                         procedure.execute(graph, null);
  49                         } else {
  50                                         procedure.execute(graph, result);
  51                         }
  52                 } catch (Throwable t) {
  53                         Logger.defaultLogError(t);
  54                                         procedure.execute(graph, null);
  55                 }
  56             }
  57         }
  58
  59     }
  60
  61     public void offer(AsyncReadGraph graph, Result result) {
  62
  63                 if(found.compareAndSet(false, true)) {
  64                         this.result = result;
  65                 } else {
  66                         // Shall fire exactly once!
  67                         if(done.compareAndSet(false, true)) {
  68                                 try {
  69                                         procedure.execute(graph, null);
  70                                 } catch (Throwable t) {
  71                                 Logger.defaultLogError(t);
  72                                         procedure.execute(graph, null);
  73                                 }
  74                         }
  75                 }
  76
  77     }
  78
  79     public void exception(AsyncReadGraph graph, Throwable t) {
  80                 // Shall fire exactly once!
  81                 if(done.compareAndSet(false, true)) {
  82                         try {
  83                                 procedure.execute(graph, null);
  84                         } catch (Throwable t2) {
  85                         Logger.defaultLogError(t);
  86                                 procedure.execute(graph, null);
  87                         }
  88                 }
  89     }
  90
  91 }