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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements. See the NOTICE file distributed with this
4    * work for additional information regarding copyright ownership. The ASF
5    * licenses this file to you under the Apache License, Version 2.0 (the
6    * "License"); you may not use this file except in compliance with the License.
7    * You may obtain a copy of the License at
8    *
9    * http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
13   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
14   * License for the specific language governing permissions and limitations
15   * under the License.
16   */
17  package org.apache.hadoop.hbase.io.encoding;
18  
19  import java.nio.ByteBuffer;
20  
21  import org.apache.hadoop.hbase.KeyValue;
22  import org.apache.hadoop.hbase.classification.InterfaceAudience;
23  import org.apache.hadoop.hbase.util.ByteBufferUtils;
24  
25  /**
26   * Stores the state of data block encoder at the beginning of new key.
27   */
28  @InterfaceAudience.Private
29  class CompressionState {
30    int keyLength;
31    int valueLength;
32  
33    short rowLength;
34    int prevOffset = FIRST_KEY;
35    byte familyLength;
36    int qualifierLength;
37    byte type;
38  
39    private final static int FIRST_KEY = -1;
40  
41    boolean isFirst() {
42      return prevOffset == FIRST_KEY;
43    }
44  
45    /**
46     * Analyze the key and fill the state.
47     * Uses mark() and reset() in ByteBuffer.
48     * @param in Buffer at the position where key starts
49     * @param keyLength Length of key in bytes
50     * @param valueLength Length of values in bytes
51     */
52    void readKey(ByteBuffer in, int keyLength, int valueLength) {
53      readKey(in, keyLength, valueLength, 0, null);
54    }
55  
56    /** 
57     * Analyze the key and fill the state assuming we know previous state.
58     * Uses mark() and reset() in ByteBuffer to avoid moving the position.
59     * <p>
60     * This method overrides all the fields of this instance, except
61     * {@link #prevOffset}, which is usually manipulated directly by encoders
62     * and decoders.
63     * @param in Buffer at the position where key starts
64     * @param keyLength Length of key in bytes
65     * @param valueLength Length of values in bytes
66     * @param commonPrefix how many first bytes are common with previous KeyValue
67     * @param previousState State from previous KeyValue
68     */
69    void readKey(ByteBuffer in, int keyLength, int valueLength,
70        int commonPrefix, CompressionState previousState) {
71      this.keyLength = keyLength;
72      this.valueLength = valueLength;
73  
74      // fill the state
75      in.mark(); // mark beginning of key
76  
77      if (commonPrefix < KeyValue.ROW_LENGTH_SIZE) {
78        rowLength = in.getShort();
79        ByteBufferUtils.skip(in, rowLength);
80  
81        familyLength = in.get();
82  
83        qualifierLength = keyLength - rowLength - familyLength -
84            KeyValue.KEY_INFRASTRUCTURE_SIZE;
85        ByteBufferUtils.skip(in, familyLength + qualifierLength);
86      } else {
87        rowLength = previousState.rowLength;
88        familyLength = previousState.familyLength;
89        qualifierLength = previousState.qualifierLength +
90            keyLength - previousState.keyLength;
91        ByteBufferUtils.skip(in, (KeyValue.ROW_LENGTH_SIZE +
92            KeyValue.FAMILY_LENGTH_SIZE) +
93            rowLength + familyLength + qualifierLength);
94      }
95  
96      readTimestamp(in);
97  
98      type = in.get();
99  
100     in.reset();
101   }
102 
103   protected void readTimestamp(ByteBuffer in) {
104     // used in subclasses to add timestamp to state
105     ByteBufferUtils.skip(in, KeyValue.TIMESTAMP_SIZE);
106   }
107 
108   void copyFrom(CompressionState state) {
109     keyLength = state.keyLength;
110     valueLength = state.valueLength;
111 
112     rowLength = state.rowLength;
113     prevOffset = state.prevOffset;
114     familyLength = state.familyLength;
115     qualifierLength = state.qualifierLength;
116     type = state.type;
117   }
118 }