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.hadoop.hbase.regionserver.wal; 20 21 import org.apache.hadoop.classification.InterfaceAudience; 22 23 /** 24 * Dictionary interface 25 * 26 * Dictionary indexes should be either bytes or shorts, only positive. (The 27 * first bit is reserved for detecting whether something is compressed or not). 28 */ 29 @InterfaceAudience.Private 30 interface Dictionary { 31 static final byte NOT_IN_DICTIONARY = -1; 32 33 /** 34 * Gets an entry from the dictionary. 35 * 36 * @param idx index of the entry 37 * @return the entry, or null if non existent 38 */ 39 public byte[] getEntry(short idx); 40 41 /** 42 * Finds the index of an entry. 43 * If no entry found, we add it. 44 * 45 * @param data the byte array that we're looking up 46 * @param offset Offset into <code>data</code> to add to Dictionary. 47 * @param length Length beyond <code>offset</code> that comprises entry; must be > 0. 48 * @return the index of the entry, or {@link #NOT_IN_DICTIONARY} if not found 49 */ 50 public short findEntry(byte[] data, int offset, int length); 51 52 /** 53 * Adds an entry to the dictionary. 54 * Be careful using this method. It will add an entry to the 55 * dictionary even if it already has an entry for the same data. 56 * Call {{@link #findEntry(byte[], int, int)}} to add without duplicating 57 * dictionary entries. 58 * 59 * @param data the entry to add 60 * @param offset Offset into <code>data</code> to add to Dictionary. 61 * @param length Length beyond <code>offset</code> that comprises entry; must be > 0. 62 * @return the index of the entry 63 */ 64 65 public short addEntry(byte[] data, int offset, int length); 66 67 /** 68 * Flushes the dictionary, empties all values. 69 */ 70 public void clear(); 71 }