code: protected void fill() throws IOException {
          ensureOpen();
          len = in.read(buf, 0, buf.length);
          if (len == -1) {
              throw new EOFException("Unexpected end of ZLIB input stream");
          }
          inf.setInput(buf, 0, len);
      }
docs: Fills input buffer with more data to decompress.
  @exception IOException if an I/O error has occurred