code: public ArrayList<FileSlice> mapBlock(int piece, long offset, int size) {
          return mapBlock(fs.map_block(piece, offset, size));
      }
docs: Returns a list of {@link com.frostwire.jlibtorrent.FileSlice} objects representing the portions of
  files the specified piece index, byte offset and size range overlaps.
  <p>
  This is the inverse mapping of {@link #mapFile(int, long, int)}.
  
  @param piece
  @param offset
  @param size
  @return