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Lucene example source code file (MappingCharFilter.java)

This example Lucene source code file (MappingCharFilter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

basecharfilter, charstream, io, ioexception, ioexception, linkedlist, linkedlist, mappingcharfilter, mappingcharfilter, normalizecharmap, normalizecharmap, override, reader, string, util

The Lucene MappingCharFilter.java source code

/**
 * 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;

import java.io.IOException;
import java.io.Reader;
import java.util.LinkedList;

/**
 * Simplistic {@link CharFilter} that applies the mappings
 * contained in a {@link NormalizeCharMap} to the character
 * stream, and correcting the resulting changes to the
 * offsets.
 */
public class MappingCharFilter extends BaseCharFilter {

  private final NormalizeCharMap normMap;
  private LinkedList<Character> buffer;
  private String replacement;
  private int charPointer;
  private int nextCharCounter;

  /** Default constructor that takes a {@link CharStream}. */
  public MappingCharFilter(NormalizeCharMap normMap, CharStream in) {
    super(in);
    this.normMap = normMap;
  }

  /** Easy-use constructor that takes a {@link Reader}. */
  public MappingCharFilter(NormalizeCharMap normMap, Reader in) {
    super(CharReader.get(in));
    this.normMap = normMap;
  }

  @Override
  public int read() throws IOException {
    while(true) {
      if (replacement != null && charPointer < replacement.length()) {
        return replacement.charAt(charPointer++);
      }

      int firstChar = nextChar();
      if (firstChar == -1) return -1;
      NormalizeCharMap nm = normMap.submap != null ?
        normMap.submap.get(Character.valueOf((char) firstChar)) : null;
      if (nm == null) return firstChar;
      NormalizeCharMap result = match(nm);
      if (result == null) return firstChar;
      replacement = result.normStr;
      charPointer = 0;
      if (result.diff != 0) {
        int prevCumulativeDiff = getLastCumulativeDiff();
        if (result.diff < 0) {
          for(int i = 0; i < -result.diff ; i++)
            addOffCorrectMap(nextCharCounter + i - prevCumulativeDiff, prevCumulativeDiff - 1 - i);
        } else {
          addOffCorrectMap(nextCharCounter - result.diff - prevCumulativeDiff, prevCumulativeDiff + result.diff);
        }
      }
    }
  }

  private int nextChar() throws IOException {
    nextCharCounter++;
    if (buffer != null && !buffer.isEmpty()) {
      return buffer.removeFirst().charValue();
    }
    return input.read();
  }

  private void pushChar(int c) {
    nextCharCounter--;
    if(buffer == null)
      buffer = new LinkedList<Character>();
    buffer.addFirst(Character.valueOf((char) c));
  }

  private void pushLastChar(int c) {
    if (buffer == null) {
      buffer = new LinkedList<Character>();
    }
    buffer.addLast(Character.valueOf((char) c));
  }

  private NormalizeCharMap match(NormalizeCharMap map) throws IOException {
    NormalizeCharMap result = null;
    if (map.submap != null) {
      int chr = nextChar();
      if (chr != -1) {
        NormalizeCharMap subMap = map.submap.get(Character.valueOf((char) chr));
        if (subMap != null) {
          result = match(subMap);
        }
        if (result == null) {
          pushChar(chr);
        }
      }
    }
    if (result == null && map.normStr != null) {
      result = map;
    }
    return result;
  }

  @Override
  public int read(char[] cbuf, int off, int len) throws IOException {
    char[] tmp = new char[len];
    int l = input.read(tmp, 0, len);
    if (l != -1) {
      for(int i = 0; i < l; i++)
        pushLastChar(tmp[i]);
    }
    l = 0;
    for(int i = off; i < off + len; i++) {
      int c = read();
      if (c == -1) break;
      cbuf[i] = (char) c;
      l++;
    }
    return l == 0 ? -1 : l;
  }
}

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