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1   /*
2    * Copyright 2010 The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  package org.apache.hadoop.hbase.util;
21  
22  import java.nio.ByteBuffer;
23  
24  /**
25   * Defines the general behavior of a bloom filter.
26   *
27   * <p>
28   * The Bloom filter is a data structure that was introduced in 1970 and that
29   * has been adopted by the networking research community in the past decade
30   * thanks to the bandwidth efficiencies that it offers for the transmission of
31   * set membership information between networked hosts. A sender encodes the
32   * information into a bit vector, the Bloom filter, that is more compact than a
33   * conventional representation. Computation and space costs for construction
34   * are linear in the number of elements. The receiver uses the filter to test
35   * whether various elements are members of the set. Though the filter will
36   * occasionally return a false positive, it will never return a false negative.
37   * When creating the filter, the sender can choose its desired point in a
38   * trade-off between the false positive rate and the size.
39   *
40   * @see BloomFilterWriter for the ability to add elements to a Bloom filter
41   */
42  public interface BloomFilter extends BloomFilterBase {
43  
44    /**
45     * Check if the specified key is contained in the bloom filter.
46     *
47     * @param buf data to check for existence of
48     * @param offset offset into the data
49     * @param length length of the data
50     * @param bloom bloom filter data to search. This can be null if auto-loading
51     *        is supported.
52     * @return true if matched by bloom, false if not
53     */
54    boolean contains(byte [] buf, int offset, int length, ByteBuffer bloom);
55  
56    /**
57     * @return true if this Bloom filter can automatically load its data
58     *         and thus allows a null byte buffer to be passed to contains()
59     */
60    boolean supportsAutoLoading();
61  }