lucene/analysis/common/src/java/org/apache/lucene/analysis/classic/ClassicTokenizer.java

/*
 * 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.lucene.analysis.classic;

import java.io.IOException;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import org.apache.lucene.analysis.tokenattributes.TypeAttribute;
import org.apache.lucene.util.AttributeFactory;

/**
 * A grammar-based tokenizer constructed with JFlex
 *
 * <p>This should be a good tokenizer for most European-language documents:
 *
 * <ul>
 *   <li>Splits words at punctuation characters, removing punctuation. However, a dot that's not
 *       followed by whitespace is considered part of a token.
 *   <li>Splits words at hyphens, unless there's a number in the token, in which case the whole
 *       token is interpreted as a product number and is not split.
 *   <li>Recognizes email addresses and internet hostnames as one token.
 * </ul>
 *
 * <p>Many applications have specific tokenizer needs. If this tokenizer does not suit your
 * application, please consider copying this source code directory to your project and maintaining
 * your own grammar-based tokenizer.
 *
 * <p>ClassicTokenizer was named StandardTokenizer in Lucene versions prior to 3.1. As of 3.1,
 * {@link StandardTokenizer} implements Unicode text segmentation, as specified by UAX#29.
 */
public final class ClassicTokenizer extends Tokenizer {
  /** A private instance of the JFlex-constructed scanner */
  private ClassicTokenizerImpl scanner;

  public static final int ALPHANUM = 0;
  public static final int APOSTROPHE = 1;
  public static final int ACRONYM = 2;
  public static final int COMPANY = 3;
  public static final int EMAIL = 4;
  public static final int HOST = 5;
  public static final int NUM = 6;
  public static final int CJ = 7;

  public static final int ACRONYM_DEP = 8;

  /** String token types that correspond to token type int constants */
  public static final String[] TOKEN_TYPES =
      new String[] {
        "<ALPHANUM>",
        "<APOSTROPHE>",
        "<ACRONYM>",
        "<COMPANY>",
        "<EMAIL>",
        "<HOST>",
        "<NUM>",
        "<CJ>",
        "<ACRONYM_DEP>"
      };

  private int skippedPositions;

  private int maxTokenLength = StandardAnalyzer.DEFAULT_MAX_TOKEN_LENGTH;

  /** Set the max allowed token length. Any token longer than this is skipped. */
  public void setMaxTokenLength(int length) {
    if (length < 1) {
      throw new IllegalArgumentException("maxTokenLength must be greater than zero");
    }
    this.maxTokenLength = length;
  }

  /** @see #setMaxTokenLength */
  public int getMaxTokenLength() {
    return maxTokenLength;
  }

  /**
   * Creates a new instance of the {@link ClassicTokenizer}. Attaches the <code>input</code> to the
   * newly created JFlex scanner.
   *
   * <p>See http://issues.apache.org/jira/browse/LUCENE-1068
   */
  public ClassicTokenizer() {
    init();
  }

  /** Creates a new ClassicTokenizer with a given {@link org.apache.lucene.util.AttributeFactory} */
  public ClassicTokenizer(AttributeFactory factory) {
    super(factory);
    init();
  }

  private void init() {
    this.scanner = new ClassicTokenizerImpl(input);
  }

  // this tokenizer generates three attributes:
  // term offset, positionIncrement and type
  private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
  private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
  private final PositionIncrementAttribute posIncrAtt =
      addAttribute(PositionIncrementAttribute.class);
  private final TypeAttribute typeAtt = addAttribute(TypeAttribute.class);

  /*
   * (non-Javadoc)
   *
   * @see org.apache.lucene.analysis.TokenStream#next()
   */
  @Override
  public final boolean incrementToken() throws IOException {
    clearAttributes();
    skippedPositions = 0;

    while (true) {
      int tokenType = scanner.getNextToken();

      if (tokenType == ClassicTokenizerImpl.YYEOF) {
        return false;
      }

      if (scanner.yylength() <= maxTokenLength) {
        posIncrAtt.setPositionIncrement(skippedPositions + 1);
        scanner.getText(termAtt);
        final int start = scanner.yychar();
        offsetAtt.setOffset(correctOffset(start), correctOffset(start + termAtt.length()));

        if (tokenType == ClassicTokenizer.ACRONYM_DEP) {
          typeAtt.setType(ClassicTokenizer.TOKEN_TYPES[ClassicTokenizer.HOST]);
          termAtt.setLength(termAtt.length() - 1); // remove extra '.'
        } else {
          typeAtt.setType(ClassicTokenizer.TOKEN_TYPES[tokenType]);
        }
        return true;
      } else
        // When we skip a too-long term, we still increment the
        // position increment
        skippedPositions++;
    }
  }

  @Override
  public final void end() throws IOException {
    super.end();
    // set final offset
    int finalOffset = correctOffset(scanner.yychar() + scanner.yylength());
    offsetAtt.setOffset(finalOffset, finalOffset);
    // adjust any skipped tokens
    posIncrAtt.setPositionIncrement(posIncrAtt.getPositionIncrement() + skippedPositions);
  }

  @Override
  public void close() throws IOException {
    super.close();
    scanner.yyreset(input);
  }

  @Override
  public void reset() throws IOException {
    super.reset();
    scanner.yyreset(input);
    skippedPositions = 0;
  }
}