| /* |
| * 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.sling.distribution.journal.impl.queue; |
| |
| import javax.annotation.CheckForNull; |
| import javax.annotation.Nonnull; |
| |
| /** |
| * A queue of {@code T} items indexed by offsets. |
| * |
| * The items are ordered in the queue according to their offset. |
| * The item with the smallest offset is the head of the queue. |
| * The item with the largest offset is the tail of the queue. |
| * |
| * @param <T> the type of the items stored in the queue |
| */ |
| public interface OffsetQueue<T> { |
| |
| /** |
| * Put an item in the queue at the given offset. |
| * |
| * @param offset the offset associated to the item |
| * @param item the item to be stored at the given offset |
| */ |
| void putItem(long offset, T item); |
| |
| /** |
| * Put all the items from the #offsetQueue in this queue. |
| * |
| * @param offsetQueue the queue to be merged into this queue |
| */ |
| void putItems(OffsetQueue<T> offsetQueue); |
| |
| /** |
| * Return the item at the given #offset. |
| * |
| * @param offset the offset of the item to be returned |
| * @return the item ; or {@code null} if no item could be found |
| * at the given offset |
| */ |
| @CheckForNull |
| T getItem(long offset); |
| |
| /** |
| * Return the item with the smallest offset in the queue. |
| * |
| * @return the first item in the queue ; or |
| * {@code null} if the queue is empty |
| */ |
| @CheckForNull |
| T getHeadItem(); |
| |
| /** |
| * Return #limit items after skipping #skip items from the queue. |
| * |
| * @param skip the number of items to skip |
| * @param limit the maximum number of items to return. -1 will return all items. |
| * @return an iterable containing the items |
| */ |
| @Nonnull |
| Iterable<T> getHeadItems(int skip, int limit); |
| |
| /** |
| * @return the smallest offset stored in the queue ; or |
| * {@code -1} if the queue is empty. |
| */ |
| long getHeadOffset(); |
| |
| /** |
| * @return the largest offset stored in the queue ; or |
| * {@code -1} if the queue is empty. |
| */ |
| long getTailOffset(); |
| |
| /** |
| * @return {@code true} if the queue is empty ; |
| * {@code false} otherwise |
| */ |
| boolean isEmpty(); |
| |
| /** |
| * @return the number of items in the queue |
| */ |
| int getSize(); |
| |
| /** |
| * Return an {@link OffsetQueue} offset queue which |
| * contains all the items from the current queue at |
| * an offset greater or equal to #minOffset. |
| * |
| * @param minOffset the minimal offset of the items |
| * in the returned offset queue |
| * @return the offset queue |
| */ |
| @Nonnull |
| OffsetQueue<T> getMinOffsetQueue(long minOffset); |
| } |