cmccabe commented on a change in pull request #9901: URL: https://github.com/apache/kafka/pull/9901#discussion_r567034077
########## File path: metadata/src/main/java/org/apache/kafka/timeline/SnapshotRegistry.java ########## @@ -0,0 +1,251 @@ +/* + * 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.kafka.timeline; + +import java.util.ArrayList; +import java.util.HashMap; +import java.util.Iterator; +import java.util.List; +import java.util.ListIterator; +import java.util.NoSuchElementException; +import java.util.stream.Collectors; + +import org.apache.kafka.common.utils.LogContext; +import org.slf4j.Logger; + + +/** + * A registry containing snapshots of timeline data structures. + * We generally expect a small number of snapshots-- perhaps 1 or 2 at a time. + * Therefore, we use ArrayLists here rather than a data structure with higher overhead. + */ +public class SnapshotRegistry { + class SnapshotIterator implements ListIterator<Snapshot> { + private Snapshot cur; + private Snapshot lastResult = null; + + SnapshotIterator(Snapshot startAfter) { + this.cur = startAfter; + } + + @Override + public boolean hasNext() { + return cur.next() != head; + } + + @Override + public Snapshot next() { + if (!hasNext()) { + throw new NoSuchElementException(); + } + cur = cur.next(); + lastResult = cur; + return cur; + } + + @Override + public boolean hasPrevious() { + return cur != head; + } + + @Override + public Snapshot previous() { + if (!hasPrevious()) { + throw new NoSuchElementException(); + } + Snapshot result = cur; Review comment: Hmm, I'm not sure I follow the question. I might be missing something. startAfter just means start after X. So if your list is A, B, C, D and you pass startAfter = B the first call to next() will return C. If, instead, you choose to iterate backwards using previous() then of course you will get B and then A. But you still "started after" B, you just chose to go backwards. ---------------------------------------------------------------- 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. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
