111 lines
2.3 KiB
Java
111 lines
2.3 KiB
Java
package org.gcube.data.streams.delegates;
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import org.gcube.data.streams.Stream;
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import org.gcube.data.streams.exceptions.StreamSkipSignal;
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import org.gcube.data.streams.exceptions.StreamStopSignal;
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import org.gcube.data.streams.generators.Generator;
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/**
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* A {@link Stream} of elements generated by unfolding the elements of an input {@link Stream} into multiple elements.
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*
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* @author Fabio Simeoni
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*
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* @param <E1> the type of elements of the input stream
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* @param <E2> the type of stream elements
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*/
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public class UnfoldedStream<E1,E2> extends AbstractDelegateStream<E1,E2> {
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private final Generator<E1, Stream<E2>> generator;
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private Stream<E2> unfold;
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/**
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* Creates an instance with a {@link Stream} and an element {@link Generator}.
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* @param stream the stream
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* @param generator the generator
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* @throws IllegalArgumentException if the stream or the generator are <code>null</code>
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*/
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public UnfoldedStream(Stream<E1> stream,Generator<E1,Stream<E2>> generator) throws IllegalArgumentException {
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super(stream);
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if (generator == null)
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throw new IllegalArgumentException("invalid null generator");
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this.generator=generator;
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}
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private RuntimeException lookAheadFailure;
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@Override
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protected E2 delegateNext() {
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return lookAheadFailureOrNextInUnfold();
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}
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@Override
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protected boolean delegateHasNext() {
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if (!hasUnfold())
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return false;
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return existsInThisOrNextUnfold();
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}
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@Override
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public void close() {
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if (unfold!=null)
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unfold.close();
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stream().close();
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}
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//helpers
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private boolean hasUnfold() {
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if (unfold==null)
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if (stream().hasNext())
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try {
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unfold = generator.yield(stream().next());
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}
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catch(StreamStopSignal stop) {
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return false;
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}
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catch(StreamSkipSignal skip) {
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return hasUnfold();
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}
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catch(RuntimeException unchecked) {
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lookAheadFailure = unchecked;
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}
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else
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return false;
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return true;
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}
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private boolean existsInThisOrNextUnfold() {
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boolean hasNext = unfold.hasNext();
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if (!hasNext) {
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unfold.close();
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unfold=null;
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return delegateHasNext();
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}
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return hasNext;
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}
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private E2 lookAheadFailureOrNextInUnfold() {
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try {
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if (lookAheadFailure!=null)
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throw lookAheadFailure;
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else
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return unfold.next();
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}
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finally {
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lookAheadFailure=null;
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}
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}
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}
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