/* |
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* Licensed to the Apache Software Foundation (ASF) under one or more |
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* contributor license agreements. See the NOTICE file distributed with |
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* this work for additional information regarding copyright ownership. |
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* The ASF licenses this file to You under the Apache License, Version 2.0 |
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* (the "License"); you may not use this file except in compliance with |
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* the License. You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0 |
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package org.apache.commons.text.translate; |
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import java.io.IOException; |
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import java.io.Writer; |
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import java.security.InvalidParameterException; |
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import java.util.BitSet; |
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import java.util.HashMap; |
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import java.util.Map; |
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/** |
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* Translates a value using a lookup table. |
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* |
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* @since 1.0 |
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*/ |
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public class LookupTranslator extends CharSequenceTranslator { |
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/** The mapping to be used in translation. */ |
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private final Map<String, String> lookupMap; |
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/** The first character of each key in the lookupMap. */ |
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private final BitSet prefixSet; |
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/** The length of the shortest key in the lookupMap. */ |
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private final int shortest; |
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/** The length of the longest key in the lookupMap. */ |
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private final int longest; |
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/** |
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* Define the lookup table to be used in translation |
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* |
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* Note that, as of Lang 3.1 (the origin of this code), the key to the lookup |
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* table is converted to a java.lang.String. This is because we need the key |
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* to support hashCode and equals(Object), allowing it to be the key for a |
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* HashMap. See LANG-882. |
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* |
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* @param lookupMap Map<CharSequence, CharSequence> table of translator |
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* mappings |
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*/ |
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public LookupTranslator(final Map<CharSequence, CharSequence> lookupMap) { |
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if (lookupMap == null) { |
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throw new InvalidParameterException("lookupMap cannot be null"); |
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} |
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this.lookupMap = new HashMap<>(); |
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this.prefixSet = new BitSet(); |
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int currentShortest = Integer.MAX_VALUE; |
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int currentLongest = 0; |
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for (final Map.Entry<CharSequence, CharSequence> pair : lookupMap.entrySet()) { |
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this.lookupMap.put(pair.getKey().toString(), pair.getValue().toString()); |
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this.prefixSet.set(pair.getKey().charAt(0)); |
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final int sz = pair.getKey().length(); |
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if (sz < currentShortest) { |
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currentShortest = sz; |
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} |
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if (sz > currentLongest) { |
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currentLongest = sz; |
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} |
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} |
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this.shortest = currentShortest; |
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this.longest = currentLongest; |
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} |
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/** |
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* {@inheritDoc} |
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*/ |
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@Override |
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public int translate(final CharSequence input, final int index, final Writer out) throws IOException { |
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// check if translation exists for the input at position index |
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if (prefixSet.get(input.charAt(index))) { |
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int max = longest; |
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if (index + longest > input.length()) { |
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max = input.length() - index; |
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} |
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// implement greedy algorithm by trying maximum match first |
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for (int i = max; i >= shortest; i--) { |
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final CharSequence subSeq = input.subSequence(index, index + i); |
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final String result = lookupMap.get(subSeq.toString()); |
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if (result != null) { |
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out.write(result); |
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return i; |
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} |
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} |
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} |
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return 0; |
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} |
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} |