Github user ajs6f commented on a diff in the pull request:
https://github.com/apache/jena/pull/157#discussion_r71167748
--- Diff:
jena-arq/src/main/java/org/apache/jena/atlas/data/SortedDataBag.java ---
@@ -69,19 +69,81 @@
protected final ThresholdPolicy<E> policy;
protected final SerializationFactory<E> serializationFactory;
- protected final Comparator<? super E> comparator;
+ protected final CanAbortComparator comparator;
protected boolean finishedAdding = false;
protected boolean spilled = false;
protected boolean closed = false;
+ protected volatile boolean cancelled;
public SortedDataBag(ThresholdPolicy<E> policy,
SerializationFactory<E> serializerFactory, Comparator<? super E> comparator)
{
this.policy = policy;
this.serializationFactory = serializerFactory;
- this.comparator = comparator;
+ this.comparator = new CanAbortComparator(comparator);
}
+ private final class CanAbortComparator implements Comparator<E>
+ {
+ /**
+ The test for whether the sort has been cancelled is
+ performed every <code>cancelTestFrequency</code>
comparisons.
+ This reduces the (presumed) overhead of access to a
+ volatile boolean.
+ */
+ static final int cancelTestFrequency = 10000;
+
+ /**
+ Count of the number of times this comparator has been
called.
+ */
+ int count = 0;
+
+ final Comparator<? super E> baseComparator;
+
+ public CanAbortComparator(Comparator<? super E> comparator)
+ {
+ this.baseComparator = comparator;
+ }
+
+ @Override public int compare(E o1, E o2)
+ {
+ count += 1;
+ if (count % cancelTestFrequency == 0)
+ {
+ if (cancelled) throw new AbandonSort();
+ }
+ return baseComparator.compare(o1, o2);
+ }
+
+ /**
+ Sort the array <code>e</code> using this comparator
+ with the additional ability to abort the sort.
+ */
+ public boolean abortableSort(E[] e) {
+ try { Arrays.sort(e, this); }
+ catch (AbandonSort s) { return true; }
--- End diff --
Maybe it's just me, but this seems a little backwardsish. I would expect
`true` to indicate successful completion. Maybe it's better to introduce a
simple `enum Finish { COMPLETED, ABORTED }` here, for clarity?
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