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     */
017    package org.apache.commons.lang3.text.translate;
018    
019    import java.io.IOException;
020    import java.io.Writer;
021    import java.util.HashMap;
022    
023    /**
024     * Translates a value using a lookup table.
025     * 
026     * @author Apache Software Foundation
027     * @since 3.0
028     * @version $Id: LookupTranslator.java 967237 2010-07-23 20:08:57Z mbenson $
029     */
030    // TODO: Replace with a RegexLookup? Performance test.
031    public class LookupTranslator extends CharSequenceTranslator {
032    
033        private final HashMap<CharSequence, CharSequence> lookupMap;
034        private final int shortest;
035        private final int longest;
036    
037        /**
038         * Define the lookup table to be used in translation
039         *
040         * @param lookup CharSequence[][] table of size [*][2]
041         */
042        public LookupTranslator(CharSequence[][] lookup) {
043            lookupMap = new HashMap<CharSequence, CharSequence>();
044            int _shortest = Integer.MAX_VALUE;
045            int _longest = 0;
046            for(CharSequence[] seq : lookup) {
047                this.lookupMap.put(seq[0], seq[1]);
048                int sz = seq[0].length();
049                if(sz < _shortest) {
050                    _shortest = sz;
051                }
052                if(sz > _longest) {
053                    _longest = sz;
054                }
055            }
056            shortest = _shortest;
057            longest = _longest;
058        }
059    
060        /**
061         * {@inheritDoc}
062         */
063        @Override
064        public int translate(CharSequence input, int index, Writer out) throws IOException {
065            int max = longest;
066            if(index + longest > input.length()) {
067                max = input.length() - index;
068            }
069            // descend so as to get a greedy algorithm
070            for(int i=max; i >= shortest; i--) {
071                CharSequence subSeq = input.subSequence(index, index + i);
072                CharSequence result = lookupMap.get(subSeq);
073                if(result != null) {
074                    out.write(result.toString());
075                    return i;
076                }
077            }
078            return 0;
079        }
080    }