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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.giraph.mapping;
20  
21  import org.apache.giraph.conf.ImmutableClassesGiraphConfigurable;
22  import org.apache.hadoop.io.Writable;
23  import org.apache.hadoop.io.WritableComparable;
24  
25  /**
26   * MappingStore used to store the vertexId - target map supplied by user
27   * Methods implemented in this class need to be thread safe
28   *
29   * @param <I> vertexId type
30   * @param <B> mappingTarget type
31   */
32  public interface MappingStore<I extends WritableComparable, B extends Writable>
33    extends ImmutableClassesGiraphConfigurable<I, Writable, Writable> {
34  
35    /**
36     * Must be called before anything else can be done
37     * on this instance
38     */
39    void initialize();
40  
41    /**
42     * Add an entry to the mapping store
43     *
44     * @param vertexId vertexId
45     * @param target target
46     */
47    void addEntry(I vertexId, B target);
48  
49    /**
50     * Get target for given vertexId
51     *
52     * @param vertexId vertexId
53     * @param target instance to use for storing target information
54     * @return target instance
55     */
56    B getTarget(I vertexId, B target);
57  
58    /**
59     * Operations to perform after adding entries
60     * to the mapping store
61     */
62    void postFilling();
63  
64    /**
65     * Get stats about the MappingStore
66     *
67     * @return numEntries
68     */
69    long getStats();
70  }