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Lucene example source code file (BaseCharFilter.java)

This example Lucene source code file (BaseCharFilter.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, basecharfilter, charfilter, charfilter, override, override

The Lucene BaseCharFilter.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 org.apache.lucene.util.ArrayUtil;

/**
 * Base utility class for implementing a {@link CharFilter}.
 * You subclass this, and then record mappings by calling
 * {@link #addOffCorrectMap}, and then invoke the correct
 * method to correct an offset.
 */
public abstract class BaseCharFilter extends CharFilter {

  private int offsets[];
  private int diffs[];
  private int size = 0;
  
  public BaseCharFilter(CharStream in) {
    super(in);
  }

  /** Retrieve the corrected offset. */
  @Override
  protected int correct(int currentOff) {
    if (offsets == null || currentOff < offsets[0]) {
      return currentOff;
    }
    
    int hi = size - 1;
    if(currentOff >= offsets[hi])
      return currentOff + diffs[hi];

    int lo = 0;
    int mid = -1;
    
    while (hi >= lo) {
      mid = (lo + hi) >>> 1;
      if (currentOff < offsets[mid])
        hi = mid - 1;
      else if (currentOff > offsets[mid])
        lo = mid + 1;
      else
        return currentOff + diffs[mid];
    }

    if (currentOff < offsets[mid])
      return mid == 0 ? currentOff : currentOff + diffs[mid-1];
    else
      return currentOff + diffs[mid];
  }
  
  protected int getLastCumulativeDiff() {
    return offsets == null ?
      0 : diffs[size-1];
  }

  protected void addOffCorrectMap(int off, int cumulativeDiff) {
    if (offsets == null) {
      offsets = new int[64];
      diffs = new int[64];
    } else if (size == offsets.length) {
      offsets = ArrayUtil.grow(offsets);
      diffs = ArrayUtil.grow(diffs);
    }
    
    offsets[size] = off;
    diffs[size++] = cumulativeDiff; 
  }
}

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