korlov42 commented on code in PR #7333: URL: https://github.com/apache/ignite-3/pull/7333#discussion_r2654926059
########## modules/core/src/main/java/org/apache/ignite/internal/util/FlatteningIterator.java: ########## @@ -0,0 +1,86 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.ignite.internal.util; + +import java.util.Iterator; +import java.util.NoSuchElementException; +import org.jetbrains.annotations.Nullable; + +/** + * An iterator which implements FLAT MAP operation on the input. + */ +public class FlatteningIterator<T> implements Iterator<T>, AutoCloseable { + private final Iterator<? extends Iterable<T>> source; + + private @Nullable Iterator<T> current; + + /** Constructs the object. */ + public FlatteningIterator(Iterator<? extends Iterable<T>> source) { + this.source = source; + } + + @Override + public boolean hasNext() { + do { + if (current != null) { + if (current.hasNext()) { + return true; + } + + // current is completely drained, reset. + current = null; + } + + if (!source.hasNext()) { + return false; + } + + current = source.next().iterator(); + } while (true); + } + + /** {@inheritDoc} */ + @Override + public T next() { + if (!hasNext()) { + throw new NoSuchElementException(); + } + + assert current != null; + + return current.next(); + } + + /** {@inheritDoc} */ + @Override + public void remove() { + if (current == null) { + throw new IllegalStateException(); + } + + current.remove(); + } + + /** {@inheritDoc} */ + @Override + public void close() throws Exception { + if (source instanceof AutoCloseable) { + ((AutoCloseable) source).close(); + } + } +} Review Comment: tests added -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
