content: package org.apache.lucene.index;
  
  /**
   * 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.
   */
  
  /** Remaps docIDs after a merge has completed, where the
   *  merged segments had at least one deletion.  This is used
   *  to renumber the buffered deletes in IndexWriter when a
   *  merge of segments with deletions commits. */
  
  final class MergeDocIDRemapper {
    int[] starts;                                 // used for binary search of mapped docID
    int[] newStarts;                              // starts, minus the deletes
    int[][] docMaps;                              // maps docIDs in the merged set
    int minDocID;                                 // minimum docID that needs renumbering
    int maxDocID;                                 // 1+ the max docID that needs renumbering
    int docShift;                                 // total # deleted docs that were compacted by this merge
  
    public MergeDocIDRemapper(SegmentInfos infos, int[][] docMaps, int[] delCounts, MergePolicy.OneMerge merge, int mergedDocCount) {
      this.docMaps = docMaps;
      SegmentInfo firstSegment = merge.segments.get(0);
      int i = 0;
      while(true) {
        SegmentInfo info = infos.info(i);
        if (info.equals(firstSegment))
          break;
        minDocID += info.docCount;
        i++;
      }
  
      int numDocs = 0;
      for(int j=0;j<docMaps.length;i++,j++) {
        numDocs += infos.info(i).docCount;
        assert infos.info(i).equals(merge.segments.get(j));
      }
      maxDocID = minDocID + numDocs;
  
      starts = new int[docMaps.length];
      newStarts = new int[docMaps.length];
  
      starts[0] = minDocID;
      newStarts[0] = minDocID;
      for(i=1;i<docMaps.length;i++) {
        final int lastDocCount = merge.segments.get(i-1).docCount;
        starts[i] = starts[i-1] + lastDocCount;
        newStarts[i] = newStarts[i-1] + lastDocCount - delCounts[i-1];
      }
      docShift = numDocs - mergedDocCount;
  
      // There are rare cases when docShift is 0.  It happens
      // if you try to delete a docID that's out of bounds,
      // because the SegmentReader still allocates deletedDocs
      // and pretends it has deletions ... so we can't make
      // this assert here
      // assert docShift > 0;
  
      // Make sure it all adds up:
      assert docShift == maxDocID - (newStarts[docMaps.length-1] + merge.segments.get(docMaps.length-1).docCount - delCounts[docMaps.length-1]);
    }
  
    public int remap(int oldDocID) {
      if (oldDocID < minDocID)
        // Unaffected by merge
        return oldDocID;
      else if (oldDocID >= maxDocID)
        // This doc was "after" the merge, so simple shift
        return oldDocID - docShift;
      else {
        // Binary search to locate this document & find its new docID
        int lo = 0;                                      // search starts array
        int hi = docMaps.length - 1;                  // for first element less
  
        while (hi >= lo) {
          int mid = (lo + hi) >>> 1;
          int midValue = starts[mid];
          if (oldDocID < midValue)
            hi = mid - 1;
          else if (oldDocID > midValue)
            lo = mid + 1;
          else {                                      // found a match
            while (mid+1 < docMaps.length && starts[mid+1] == midValue) {
              mid++;                                  // scan to last match
            }
            if (docMaps[mid] != null)
              return newStarts[mid] + docMaps[mid][oldDocID-starts[mid]];
            else
              return newStarts[mid] + oldDocID-starts[mid];
          }
        }
        if (docMaps[hi] != null)
          return newStarts[hi] + docMaps[hi][oldDocID-starts[hi]];
        else
          return newStarts[hi] + oldDocID-starts[hi];
      }
    }
  }
  