102 lines
3.7 KiB
Java
102 lines
3.7 KiB
Java
/*
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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.HashMap;
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import java.util.HashSet;
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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 HashSet<Character> 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 orgin 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 HashSet<>();
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int currentShortest = Integer.MAX_VALUE;
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int currentLongest = 0;
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for (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.add(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.contains(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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}
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