bundles/org.simantics.graphviz/src/org/simantics/graphviz/continuation/Computation.java

   1 package org.simantics.graphviz.continuation;
   2
   3 import java.util.ArrayList;
   4 import java.util.concurrent.CancellationException;
   5 import java.util.concurrent.CountDownLatch;
   6
   7 public abstract class Computation<T> {
   8     T result;
   9     Exception exception;
  10     ArrayList<Continuation<T>> continuations = new ArrayList<Continuation<T>>();
  11     CountDownLatch doneGate = new CountDownLatch(1);
  12
  13     public void addContinuation(Continuation<T> continuation) {
  14         synchronized(doneGate) {
  15             if(doneGate.getCount() == 0) {
  16                 if(exception == null)
  17                     continuation.succeeded(result);
  18                 else
  19                     continuation.failed(exception);
  20             }
  21             else
  22                 continuations.add(continuation);
  23         }
  24     }
  25
  26     public boolean isDone() {
  27         return doneGate.getCount() == 0;
  28     }
  29
  30     protected void failWith(Exception exception) {
  31         this.exception = exception;
  32         ArrayList<Continuation<T>> cs;
  33         synchronized (doneGate) {
  34             cs = this.continuations;
  35             this.continuations = null;
  36             doneGate.countDown();
  37         }
  38         if(cs != null)
  39             for(Continuation<T> continuation : cs)
  40                 continuation.failed(exception);
  41     }
  42
  43     protected void doneWith(T result) {
  44         this.result = result;
  45         ArrayList<Continuation<T>> cs;
  46         synchronized (doneGate) {
  47             cs = this.continuations;
  48             this.continuations = null;
  49             doneGate.countDown();
  50         }
  51         if(cs != null)
  52             for(Continuation<T> continuation : cs)
  53                 continuation.succeeded(result);
  54     }
  55
  56     public void cancel() {
  57         failWith(new CancellationException());
  58     }
  59
  60     public T get() throws Exception {
  61         doneGate.await();
  62         if(exception != null)
  63             throw exception;
  64         return result;
  65     }
  66 }