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1   /*
2    * Copyright 2015 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.util.internal;
17  
18  /**
19   * Provides methods for {@link DefaultPriorityQueue} to maintain internal state. These methods should generally not be
20   * used outside the scope of {@link DefaultPriorityQueue}.
21   */
22  public interface PriorityQueueNode {
23      /**
24       * This should be used to initialize the storage returned by {@link #priorityQueueIndex(DefaultPriorityQueue)}.
25       */
26      int INDEX_NOT_IN_QUEUE = -1;
27  
28      /**
29       * Get the last value set by {@link #priorityQueueIndex(DefaultPriorityQueue, int)} for the value corresponding to
30       * {@code queue}.
31       * <p>
32       * Throwing exceptions from this method will result in undefined behavior.
33       */
34      int priorityQueueIndex(DefaultPriorityQueue<?> queue);
35  
36      /**
37       * Used by {@link DefaultPriorityQueue} to maintain state for an element in the queue.
38       * <p>
39       * Throwing exceptions from this method will result in undefined behavior.
40       * @param queue The queue for which the index is being set.
41       * @param i The index as used by {@link DefaultPriorityQueue}.
42       */
43      void priorityQueueIndex(DefaultPriorityQueue<?> queue, int i);
44  }