001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.io.util;
019
020import java.io.IOException;
021import java.io.OutputStream;
022import java.nio.ByteBuffer;
023import org.apache.hadoop.hbase.util.ByteBufferUtils;
024import org.apache.yetus.audience.InterfaceAudience;
025
026/**
027 * Dictionary interface Dictionary indexes should be either bytes or shorts, only positive. (The
028 * first bit is reserved for detecting whether something is compressed or not).
029 */
030@InterfaceAudience.Private
031public interface Dictionary {
032  byte NOT_IN_DICTIONARY = -1;
033
034  void init(int initialSize);
035
036  /**
037   * Gets an entry from the dictionary.
038   * @param idx index of the entry
039   * @return the entry, or null if non existent
040   */
041  byte[] getEntry(short idx);
042
043  /**
044   * Finds the index of an entry. If no entry found, we add it.
045   * @param data   the byte array that we're looking up
046   * @param offset Offset into <code>data</code> to add to Dictionary.
047   * @param length Length beyond <code>offset</code> that comprises entry; must be &gt; 0.
048   * @return the index of the entry, or {@link #NOT_IN_DICTIONARY} if not found
049   */
050  short findEntry(byte[] data, int offset, int length);
051
052  /**
053   * Finds the index of an entry. If no entry found, we add it.
054   * @param data   the ByteBuffer that we're looking up
055   * @param offset Offset into <code>data</code> to add to Dictionary.
056   * @param length Length beyond <code>offset</code> that comprises entry; must be &gt; 0.
057   * @return the index of the entry, or {@link #NOT_IN_DICTIONARY} if not found
058   */
059  short findEntry(ByteBuffer data, int offset, int length);
060
061  /**
062   * Adds an entry to the dictionary. Be careful using this method. It will add an entry to the
063   * dictionary even if it already has an entry for the same data. Call
064   * {{@link #findEntry(byte[], int, int)}} to add without duplicating dictionary entries.
065   * @param data   the entry to add
066   * @param offset Offset into <code>data</code> to add to Dictionary.
067   * @param length Length beyond <code>offset</code> that comprises entry; must be &gt; 0.
068   * @return the index of the entry
069   */
070  short addEntry(byte[] data, int offset, int length);
071
072  /**
073   * Flushes the dictionary, empties all values.
074   */
075  void clear();
076
077  /**
078   * Helper methods to write the dictionary data to the OutputStream
079   * @param out    the outputstream to which data needs to be written
080   * @param data   the data to be written in byte[]
081   * @param offset the offset
082   * @param length length to be written
083   * @param dict   the dictionary whose contents are to written n
084   */
085  public static void write(OutputStream out, byte[] data, int offset, int length, Dictionary dict)
086    throws IOException {
087    short dictIdx = Dictionary.NOT_IN_DICTIONARY;
088    if (dict != null) {
089      dictIdx = dict.findEntry(data, offset, length);
090    }
091    if (dictIdx == Dictionary.NOT_IN_DICTIONARY) {
092      out.write(Dictionary.NOT_IN_DICTIONARY);
093      StreamUtils.writeRawVInt32(out, length);
094      out.write(data, offset, length);
095    } else {
096      StreamUtils.writeShort(out, dictIdx);
097    }
098  }
099
100  /**
101   * Helper methods to write the dictionary data to the OutputStream
102   * @param out    the outputstream to which data needs to be written
103   * @param data   the data to be written in ByteBuffer
104   * @param offset the offset
105   * @param length length to be written
106   * @param dict   the dictionary whose contents are to written n
107   */
108  public static void write(OutputStream out, ByteBuffer data, int offset, int length,
109    Dictionary dict) throws IOException {
110    short dictIdx = Dictionary.NOT_IN_DICTIONARY;
111    if (dict != null) {
112      dictIdx = dict.findEntry(data, offset, length);
113    }
114    if (dictIdx == Dictionary.NOT_IN_DICTIONARY) {
115      out.write(Dictionary.NOT_IN_DICTIONARY);
116      StreamUtils.writeRawVInt32(out, length);
117      ByteBufferUtils.copyBufferToStream(out, data, offset, length);
118    } else {
119      StreamUtils.writeShort(out, dictIdx);
120    }
121  }
122}