public void seek(TermEnum terms) throws IOException {
      original.seek(terms);

      docFreq = terms.docFreq();
      pointer = -1;

      if (docFreq > postingMaps.length) { // grow postingsMap
        PostingMap[] newMap = new PostingMap[docFreq];
        System.arraycopy(postingMaps, 0, newMap, 0, postingMaps.length);
        for (int i = postingMaps.length; i < docFreq; i++) {
          newMap[i] = new PostingMap();
        }
        postingMaps = newMap;
      }

      out.reset();

      int i = 0;
      while (original.next()) {
        PostingMap map = postingMaps[i++];
        map.newDoc = oldToNew[original.doc()]; // remap the newDoc id
        map.offset = out.getFilePointer(); // save pointer to buffer

        final int tf = original.freq(); // buffer tf & positions
        out.writeVInt(tf);
        int prevPosition = 0;
        for (int j = tf; j > 0; j--) { // delta encode positions
          int p = original.nextPosition();
          out.writeVInt(p - prevPosition);
          prevPosition = p;
        }
      }
      out.flush();
      docFreq = i; // allow for deletions

      Arrays.sort(postingMaps, 0, docFreq); // resort by mapped doc ids
      // HeapSorter.sort(postingMaps,docFreq); // TODO MC - due to the lack of space

      // NOTE: this might be substantially faster if RAMInputStream were public
      // and supported a reset() operation.
      in = tempDir.openInput(TEMP_FILE);
    }
 public void close() throws IOException {
   original.close();
 }