content: /**
   * 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; 
    }
  }
  