bundles/org.simantics.db.impl/src/org/simantics/db/impl/query/ExternalReadEntry.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.impl.query;
  13
  14 import java.util.ArrayList;
  15 import java.util.LinkedList;
  16
  17 import org.simantics.db.exception.DatabaseException;
  18 import org.simantics.db.impl.DebugPolicy;
  19 import org.simantics.db.impl.graph.ReadGraphImpl;
  20 import org.simantics.db.procedure.AsyncProcedure;
  21 import org.simantics.db.procedure.Procedure;
  22 import org.simantics.db.request.ExternalRead;
  23 import org.simantics.db.request.RequestFlags;
  24
  25 final public class ExternalReadEntry<T> extends CacheEntryBase<AsyncProcedure<T>> {
  26
  27     final LinkedList<T> items = new LinkedList<T>();
  28
  29     protected ExternalRead<T> request;
  30
  31     @Override
  32     int makeHash() {
  33         return request.hashCode();
  34     }
  35
  36     @Override
  37     public Object getOriginalRequest() {
  38         return request;
  39     }
  40
  41     @Override
  42     public void clearResult(QuerySupport support) {
  43     }
  44
  45     @Override
  46     public void discard() {
  47         request.unregistered();
  48         request = null;
  49         super.discard();
  50     }
  51
  52     @Override
  53     public void setPending() {
  54         if(result != NO_RESULT) {
  55             //new Exception("result = " + result).printStackTrace();
  56         }
  57         statusOrException = PENDING;
  58         result = REQUIRES_COMPUTATION;
  59     }
  60
  61     public ExternalReadEntry(ExternalRead<T> request) {
  62         assert request != null;
  63         this.request = request;
  64     }
  65
  66     final public void queue(T item) {
  67         synchronized(items) {
  68                 items.addLast(item);
  69                 // TODO: implement flags/logic in ExternalRead to state that all but the latest request result can be evaporated
  70                 // In some cases where data is produced really fast this might be necessary but currently this queueing will do.
  71         }
  72     }
  73
  74     final public void addOrSet(QueryProcessor processor, Object item) {
  75
  76         try {
  77
  78             assert(isPending());
  79
  80             ArrayList<Procedure<T>> p = null;
  81
  82             synchronized(this) {
  83
  84                 setResult(item);
  85                 setReady();
  86 //                p = procs;
  87 //                procs = null;
  88
  89             }
  90
  91 //            if(p != null)
  92 //                for(Procedure proc : p) {
  93 //                    proc.execute((T)item);
  94 //                }
  95
  96         } catch (Throwable t) {
  97             t.printStackTrace();
  98         }
  99
 100     }
 101
 102     @Override
 103     public void except(Throwable t) {
 104         if(DebugPolicy.QUERY_STATE) System.out.println("[QUERY STATE]: excepted " + this);
 105         if(statusOrException != DISCARDED) {
 106             statusOrException = EXCEPTED;
 107             result = t;
 108         } else {
 109             result = t;
 110         }
 111         assert(isExcepted());
 112     }
 113
 114     @Override
 115     public void setResult(Object result) {
 116         super.setResult(result);
 117         assert(!(result instanceof Throwable));
 118         assert(!isExcepted());
 119     }
 120
 121     @Override
 122     final public Query getQuery() {
 123
 124         return new Query() {
 125
 126                         @Override
 127                         public void recompute(ReadGraphImpl graph) {
 128
 129                                 synchronized(items) {
 130
 131
 132                                         // Update
 133                                         if(!items.isEmpty()) {
 134                                             setReady();
 135                                                 setResult(items.removeFirst());
 136                                         }
 137                                         // Reschedule
 138                                         if(!items.isEmpty()) {
 139                                                 graph.processor.updatePrimitive(request);
 140                                         }
 141
 142                                 }
 143
 144                         }
 145
 146                         @Override
 147                         public void removeEntry(QueryProcessor processor) {
 148                                 processor.cache.remove(ExternalReadEntry.this);
 149                         }
 150
 151                         @Override
 152                         public int type() {
 153                                 return RequestFlags.IMMEDIATE_UPDATE;
 154                         }
 155
 156                         @Override
 157                         public String toString() {
 158                                 if(request == null) return "DISCARDED ExternalRead";
 159                                 else return request.toString();
 160                         }
 161
 162         };
 163
 164     }
 165
 166         @Override
 167         public String toString() {
 168                 if(request == null) return "DISCARDED ExternalRead " + System.identityHashCode(this);
 169                 else return request.toString() + " " + + System.identityHashCode(this);
 170         }
 171
 172     @Override
 173     public Object performFromCache(ReadGraphImpl graph, AsyncProcedure<T> procedure) {
 174
 175         AsyncProcedure<T> proc = (AsyncProcedure<T>)procedure;
 176
 177             if(isExcepted()) {
 178
 179             proc.exception(graph, (Throwable)getResult());
 180
 181         } else {
 182
 183             proc.execute(graph, (T)getResult());
 184
 185         }
 186
 187             return getResult();
 188
 189     }
 190
 191     @Override
 192     void prepareRecompute(QuerySupport querySupport) {
 193         // Do nothing - the state is already set and cannot be recomputed on demand
 194     }
 195
 196         @Override
 197         public Object compute(ReadGraphImpl graph, AsyncProcedure<T> procedure) throws DatabaseException {
 198         return graph.processor.cache.performQuery(graph, request, this, procedure);
 199         }
 200
 201 }