org.apache.commons.text.translate.LookupTranslator Maven / Gradle / Ivy
/*
*
* * The MIT License (MIT)
* *
* * Copyright (c) 2018 XiaoMiSum ([email protected])
* *
* * Permission is hereby granted, free of charge, to any person obtaining
* * a copy of this software and associated documentation files (the
* * 'Software'), to deal in the Software without restriction, including
* * without limitation the rights to use, copy, modify, merge, publish,
* * distribute, sublicense, and/or sell copies of the Software, and to
* * permit persons to whom the Software is furnished to do so, subject to
* * the following conditions:
* *
* * The above copyright notice and this permission notice shall be
* * included in all copies or substantial portions of the Software.
* *
* * THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
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* * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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package org.apache.commons.text.translate;
import java.io.IOException;
import java.io.Writer;
import java.security.InvalidParameterException;
import java.util.BitSet;
import java.util.HashMap;
import java.util.Map;
/**
* https://gitee.com/mirrors/commons-text
*
* Translates a value using a lookup table.
*
* @since 1.0
*/
public class LookupTranslator extends CharSequenceTranslator {
/** The mapping to be used in translation. */
private final Map lookupMap;
/** The first character of each key in the lookupMap. */
private final BitSet prefixSet;
/** The length of the shortest key in the lookupMap. */
private final int shortest;
/** The length of the longest key in the lookupMap. */
private final int longest;
/**
* Define the lookup table to be used in translation
*
* Note that, as of Lang 3.1 (the origin of this code), the key to the lookup
* table is converted to a java.lang.String. This is because we need the key
* to support hashCode and equals(Object), allowing it to be the key for a
* HashMap. See LANG-882.
*
* @param lookupMap Map<CharSequence, CharSequence> table of translator
* mappings
*/
public LookupTranslator(final Map lookupMap) {
if (lookupMap == null) {
throw new InvalidParameterException("lookupMap cannot be null");
}
this.lookupMap = new HashMap<>();
this.prefixSet = new BitSet();
int currentShortest = Integer.MAX_VALUE;
int currentLongest = 0;
for (final Map.Entry pair : lookupMap.entrySet()) {
this.lookupMap.put(pair.getKey().toString(), pair.getValue().toString());
this.prefixSet.set(pair.getKey().charAt(0));
final int sz = pair.getKey().length();
if (sz < currentShortest) {
currentShortest = sz;
}
if (sz > currentLongest) {
currentLongest = sz;
}
}
this.shortest = currentShortest;
this.longest = currentLongest;
}
/**
* {@inheritDoc}
*/
@Override
public int translate(final CharSequence input, final int index, final Writer out) throws IOException {
// check if translation exists for the input at position index
if (prefixSet.get(input.charAt(index))) {
int max = longest;
if (index + longest > input.length()) {
max = input.length() - index;
}
// implement greedy algorithm by trying maximum match first
for (int i = max; i >= shortest; i--) {
final CharSequence subSeq = input.subSequence(index, index + i);
final String result = lookupMap.get(subSeq.toString());
if (result != null) {
out.write(result);
return i;
}
}
}
return 0;
}
}
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