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