001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.text.translate; 018 019import java.io.IOException; 020import java.io.Writer; 021import java.security.InvalidParameterException; 022import java.util.BitSet; 023import java.util.HashMap; 024import java.util.Map; 025 026/** 027 * Translates a value using a lookup table. 028 * 029 * @since 1.0 030 */ 031public class LookupTranslator extends CharSequenceTranslator { 032 033 /** The mapping to be used in translation. */ 034 private final Map<String, String> lookupMap; 035 /** The first character of each key in the lookupMap. */ 036 private final BitSet prefixSet; 037 /** The length of the shortest key in the lookupMap. */ 038 private final int shortest; 039 /** The length of the longest key in the lookupMap. */ 040 private final int longest; 041 042 /** 043 * Define the lookup table to be used in translation 044 * 045 * Note that, as of Lang 3.1 (the origin of this code), the key to the lookup 046 * table is converted to a java.lang.String. This is because we need the key 047 * to support hashCode and equals(Object), allowing it to be the key for a 048 * HashMap. See LANG-882. 049 * 050 * @param lookupMap Map<CharSequence, CharSequence> table of translator 051 * mappings 052 */ 053 public LookupTranslator(final Map<CharSequence, CharSequence> lookupMap) { 054 if (lookupMap == null) { 055 throw new InvalidParameterException("lookupMap cannot be null"); 056 } 057 this.lookupMap = new HashMap<>(); 058 this.prefixSet = new BitSet(); 059 int currentShortest = Integer.MAX_VALUE; 060 int currentLongest = 0; 061 062 for (final Map.Entry<CharSequence, CharSequence> pair : lookupMap.entrySet()) { 063 this.lookupMap.put(pair.getKey().toString(), pair.getValue().toString()); 064 this.prefixSet.set(pair.getKey().charAt(0)); 065 final int sz = pair.getKey().length(); 066 if (sz < currentShortest) { 067 currentShortest = sz; 068 } 069 if (sz > currentLongest) { 070 currentLongest = sz; 071 } 072 } 073 this.shortest = currentShortest; 074 this.longest = currentLongest; 075 } 076 077 /** 078 * {@inheritDoc} 079 */ 080 @Override 081 public int translate(final CharSequence input, final int index, final Writer out) throws IOException { 082 // check if translation exists for the input at position index 083 if (prefixSet.get(input.charAt(index))) { 084 int max = longest; 085 if (index + longest > input.length()) { 086 max = input.length() - index; 087 } 088 // implement greedy algorithm by trying maximum match first 089 for (int i = max; i >= shortest; i--) { 090 final CharSequence subSeq = input.subSequence(index, index + i); 091 final String result = lookupMap.get(subSeq.toString()); 092 093 if (result != null) { 094 out.write(result); 095 return i; 096 } 097 } 098 } 099 return 0; 100 } 101}