org.apache.solr.analysis.LowerCaseTokenizer Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.solr.analysis;
import java.io.IOException;
import org.apache.lucene.analysis.CharacterUtils;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.core.LetterTokenizer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.util.AttributeFactory;
/**
* LowerCaseTokenizer performs the function of LetterTokenizer
* and LowerCaseFilter together. It divides text at non-letters and converts
* them to lower case. While it is functionally equivalent to the combination
* of LetterTokenizer and LowerCaseFilter, there is a performance advantage
* to doing the two tasks at once, hence this (redundant) implementation.
*
* Note: this does a decent job for most European languages, but does a terrible
* job for some Asian languages, where words are not separated by spaces.
*
*
* @deprecated Use {@link LetterTokenizer} and {@link org.apache.lucene.analysis.LowerCaseFilter}
*/
@Deprecated
public final class LowerCaseTokenizer extends Tokenizer {
/**
* Construct a new LowerCaseTokenizer.
*/
public LowerCaseTokenizer() {
this.maxTokenLen = DEFAULT_MAX_WORD_LEN;
}
/**
* Construct a new LowerCaseTokenizer using a given
* {@link org.apache.lucene.util.AttributeFactory}.
*
* @param factory
* the attribute factory to use for this {@link Tokenizer}
*/
public LowerCaseTokenizer(AttributeFactory factory) {
this(factory, DEFAULT_MAX_WORD_LEN);
}
/**
* Construct a new LowerCaseTokenizer using a given
* {@link org.apache.lucene.util.AttributeFactory}.
*
* @param factory the attribute factory to use for this {@link Tokenizer}
* @param maxTokenLen maximum token length the tokenizer will emit.
* Must be greater than 0 and less than MAX_TOKEN_LENGTH_LIMIT (1024*1024)
* @throws IllegalArgumentException if maxTokenLen is invalid.
*/
public LowerCaseTokenizer(AttributeFactory factory, int maxTokenLen) {
super(factory);
this.maxTokenLen = maxTokenLen;
}
private int offset = 0, bufferIndex = 0, dataLen = 0, finalOffset = 0;
public static final int DEFAULT_MAX_WORD_LEN = 255;
private static final int IO_BUFFER_SIZE = 4096;
private final int maxTokenLen;
private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
private final CharacterUtils.CharacterBuffer ioBuffer = CharacterUtils.newCharacterBuffer(IO_BUFFER_SIZE);
@Override
public final boolean incrementToken() throws IOException {
clearAttributes();
int length = 0;
int start = -1; // this variable is always initialized
int end = -1;
char[] buffer = termAtt.buffer();
while (true) {
if (bufferIndex >= dataLen) {
offset += dataLen;
CharacterUtils.fill(ioBuffer, input); // read supplementary char aware with CharacterUtils
if (ioBuffer.getLength() == 0) {
dataLen = 0; // so next offset += dataLen won't decrement offset
if (length > 0) {
break;
} else {
finalOffset = correctOffset(offset);
return false;
}
}
dataLen = ioBuffer.getLength();
bufferIndex = 0;
}
// use CharacterUtils here to support < 3.1 UTF-16 code unit behavior if the char based methods are gone
final int c = Character.codePointAt(ioBuffer.getBuffer(), bufferIndex, ioBuffer.getLength());
final int charCount = Character.charCount(c);
bufferIndex += charCount;
if (Character.isLetter(c)) { // if it's a token char
if (length == 0) { // start of token
assert start == -1;
start = offset + bufferIndex - charCount;
end = start;
} else if (length >= buffer.length-1) { // check if a supplementary could run out of bounds
buffer = termAtt.resizeBuffer(2+length); // make sure a supplementary fits in the buffer
}
end += charCount;
length += Character.toChars(Character.toLowerCase(c), buffer, length); // buffer it, normalized
if (length >= maxTokenLen) { // buffer overflow! make sure to check for >= surrogate pair could break == test
break;
}
} else if (length > 0) { // at non-Letter w/ chars
break; // return 'em
}
}
termAtt.setLength(length);
assert start != -1;
offsetAtt.setOffset(correctOffset(start), finalOffset = correctOffset(end));
return true;
}
@Override
public final void end() throws IOException {
super.end();
// set final offset
offsetAtt.setOffset(finalOffset, finalOffset);
}
@Override
public void reset() throws IOException {
super.reset();
bufferIndex = 0;
offset = 0;
dataLen = 0;
finalOffset = 0;
ioBuffer.reset(); // make sure to reset the IO buffer!!
}
}