code: public ArchiveRecord get(long offset) throws IOException {
          cleanupCurrentRecord();
          long posn = positionForRecord(in); 
          if(offset>=posn) {
              in.skip(offset-posn); 
          } else {
              throw new UnsupportedOperationException("no reverse seeking: at "+posn+" requested "+offset); 
          }
          return createArchiveRecord(this.in, offset);
      }
docs: Get record at passed <code>offset</code>.
  
  @param offset Byte index into file at which a record starts.
  @return An Archive Record reference.
  @throws IOException