+++ /dev/null
-package org.apache.lucene.analysis.ngram;
-
-/**
- * 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.
- */
-
-import org.apache.lucene.analysis.Tokenizer;
-import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
-import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
-import org.apache.lucene.util.AttributeSource;
-
-import java.io.IOException;
-import java.io.Reader;
-
-/**
- * Tokenizes the input into n-grams of the given size(s).
- */
-public final class NGramTokenizer extends Tokenizer {
- public static final int DEFAULT_MIN_NGRAM_SIZE = 1;
- public static final int DEFAULT_MAX_NGRAM_SIZE = 2;
-
- private int minGram, maxGram;
- private int gramSize;
- private int pos = 0;
- private int inLen;
- private String inStr;
- private boolean started = false;
-
- private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
- private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
-
- /**
- * Creates NGramTokenizer with given min and max n-grams.
- * @param input {@link Reader} holding the input to be tokenized
- * @param minGram the smallest n-gram to generate
- * @param maxGram the largest n-gram to generate
- */
- public NGramTokenizer(Reader input, int minGram, int maxGram) {
- super(input);
- init(minGram, maxGram);
- }
-
- /**
- * Creates NGramTokenizer with given min and max n-grams.
- * @param source {@link AttributeSource} to use
- * @param input {@link Reader} holding the input to be tokenized
- * @param minGram the smallest n-gram to generate
- * @param maxGram the largest n-gram to generate
- */
- public NGramTokenizer(AttributeSource source, Reader input, int minGram, int maxGram) {
- super(source, input);
- init(minGram, maxGram);
- }
-
- /**
- * Creates NGramTokenizer with given min and max n-grams.
- * @param factory {@link org.apache.lucene.util.AttributeSource.AttributeFactory} to use
- * @param input {@link Reader} holding the input to be tokenized
- * @param minGram the smallest n-gram to generate
- * @param maxGram the largest n-gram to generate
- */
- public NGramTokenizer(AttributeFactory factory, Reader input, int minGram, int maxGram) {
- super(factory, input);
- init(minGram, maxGram);
- }
-
- /**
- * Creates NGramTokenizer with default min and max n-grams.
- * @param input {@link Reader} holding the input to be tokenized
- */
- public NGramTokenizer(Reader input) {
- this(input, DEFAULT_MIN_NGRAM_SIZE, DEFAULT_MAX_NGRAM_SIZE);
- }
-
- private void init(int minGram, int maxGram) {
- if (minGram < 1) {
- throw new IllegalArgumentException("minGram must be greater than zero");
- }
- if (minGram > maxGram) {
- throw new IllegalArgumentException("minGram must not be greater than maxGram");
- }
- this.minGram = minGram;
- this.maxGram = maxGram;
- }
-
- /** Returns the next token in the stream, or null at EOS. */
- @Override
- public final boolean incrementToken() throws IOException {
- clearAttributes();
- if (!started) {
- started = true;
- gramSize = minGram;
- char[] chars = new char[1024];
- input.read(chars);
- inStr = new String(chars).trim(); // remove any trailing empty strings
- inLen = inStr.length();
- }
-
- if (pos+gramSize > inLen) { // if we hit the end of the string
- pos = 0; // reset to beginning of string
- gramSize++; // increase n-gram size
- if (gramSize > maxGram) // we are done
- return false;
- if (pos+gramSize > inLen)
- return false;
- }
-
- int oldPos = pos;
- pos++;
- termAtt.setEmpty().append(inStr, oldPos, oldPos+gramSize);
- offsetAtt.setOffset(correctOffset(oldPos), correctOffset(oldPos+gramSize));
- return true;
- }
-
- @Override
- public final void end() {
- // set final offset
- final int finalOffset = inLen;
- this.offsetAtt.setOffset(finalOffset, finalOffset);
- }
-
- @Override
- public void reset(Reader input) throws IOException {
- super.reset(input);
- reset();
- }
-
- @Override
- public void reset() throws IOException {
- super.reset();
- started = false;
- pos = 0;
- }
-}
fnp / pylucene.git / blobdiff