bundles/org.simantics.db.common/src/org/simantics/db/common/procedure/single/wrapper/NullSingleOrExceptionProcedure.java

   1 /*******************************************************************************\r
   2  * Copyright (c) 2007, 2010 Association for Decentralized Information Management\r
   3  * in Industry THTH ry.\r
   4  * All rights reserved. This program and the accompanying materials\r
   5  * are made available under the terms of the Eclipse Public License v1.0\r
   6  * which accompanies this distribution, and is available at\r
   7  * http://www.eclipse.org/legal/epl-v10.html\r
   8  *\r
   9  * Contributors:\r
  10  *     VTT Technical Research Centre of Finland - initial API and implementation\r
  11  *******************************************************************************/\r
  12 package org.simantics.db.common.procedure.single.wrapper;\r
  13 \r
  14 import java.util.concurrent.atomic.AtomicBoolean;\r
  15 import java.util.concurrent.atomic.AtomicInteger;\r
  16 \r
  17 import org.simantics.db.AsyncReadGraph;\r
  18 import org.simantics.db.common.utils.Logger;\r
  19 import org.simantics.db.exception.NoSingleResultException;\r
  20 import org.simantics.db.procedure.AsyncProcedure;\r
  21 \r
  22 final public class NullSingleOrExceptionProcedure<Result> {\r
  23 \r
  24         private Result result = null;\r
  25         final AsyncProcedure<Result> procedure;\r
  26         final AtomicBoolean done = new AtomicBoolean(false);\r
  27         final AtomicBoolean found = new AtomicBoolean(false);\r
  28         final AtomicInteger ready = new AtomicInteger(1);\r
  29 \r
  30         public NullSingleOrExceptionProcedure(AsyncProcedure<Result> procedure) {\r
  31 \r
  32                 this.procedure = procedure;\r
  33 \r
  34         }\r
  35 \r
  36         public void inc() {\r
  37 \r
  38                 ready.incrementAndGet();\r
  39 \r
  40         }\r
  41 \r
  42         public void dec(AsyncReadGraph graph) {\r
  43 \r
  44                 if(ready.decrementAndGet() == 0) {\r
  45                         // Shall fire exactly once!\r
  46                         if(done.compareAndSet(false, true)) {\r
  47                                 try {\r
  48                                         procedure.execute(graph, result);\r
  49                                 } catch (Throwable t) {\r
  50                                 Logger.defaultLogError(t);\r
  51                                 }\r
  52                         }\r
  53                 }\r
  54 \r
  55         }\r
  56 \r
  57         public void offer(AsyncReadGraph graph, Result result) {\r
  58 \r
  59                 if(found.compareAndSet(false, true)) {\r
  60                         this.result = result;\r
  61                 } else {\r
  62                         // Shall fire exactly once!\r
  63                         if(done.compareAndSet(false, true)) {\r
  64                                 try {\r
  65                                         procedure.exception(graph, new NoSingleResultException(procedure.toString()));\r
  66                                 } catch (Throwable t) {\r
  67                                 Logger.defaultLogError(t);\r
  68                                 }\r
  69                         }\r
  70                 }\r
  71 \r
  72         }\r
  73 \r
  74         public void exception(AsyncReadGraph graph, Throwable t) {\r
  75                 // Shall fire exactly once!\r
  76                 if(done.compareAndSet(false, true)) {\r
  77                         try {\r
  78                                 procedure.exception(graph, t);\r
  79                         } catch (Throwable t2) {\r
  80                         Logger.defaultLogError(t2);\r
  81                         }\r
  82                 }\r
  83         }\r
  84 \r
  85 }\r