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