bundles/org.simantics.db.impl/src/org/simantics/db/impl/query/PendingTaskSupport.java

   1 package org.simantics.db.impl.query;
   2
   3 import java.util.ArrayList;
   4 import java.util.Collection;
   5
   6 import org.simantics.db.impl.query.QueryProcessor.SessionTask;
   7
   8 /*
   9  * Support class for queuing pending tasks to be executed when result gets ready
  10  */
  11 public class PendingTaskSupport {
  12
  13     private ArrayList<SessionTask> pendingTasks;
  14     private IPending pending;
  15
  16     public PendingTaskSupport(IPending pending) {
  17         this.pending = pending;
  18     }
  19
  20     /*
  21      * We assume here that the associated IPending performs this atomically
  22      * The caller is responsible for execution of the returned task after the critical section
  23      */
  24     public boolean executeWhenResultIsAvailable(SessionTask task) {
  25         if(pending.isPending()) {
  26             if(pendingTasks == null)
  27                 pendingTasks = new ArrayList<SessionTask>();
  28             pendingTasks.add(task);
  29             return false;
  30         } else {
  31             return true;
  32         }
  33     }
  34
  35     /*
  36      * We assume here that the associated IPending performs this atomically after changing the pending result
  37      * The caller is responsible for execution of the returned task after the critical section
  38      */
  39     public Collection<SessionTask> executePending() {
  40         ArrayList<SessionTask> ret = pendingTasks;
  41         pendingTasks = null;
  42         return ret;
  43     }
  44
  45 }