code: public MessagePacker packBinaryHeader(int len)
              throws IOException
      {
          if (len < (1 << 8)) {
              writeByteAndByte(BIN8, (byte) len);
          }
          else if (len < (1 << 16)) {
              writeByteAndShort(BIN16, (short) len);
          }
          else {
              writeByteAndInt(BIN32, len);
          }
          return this;
      }
docs: Writes header of a Binary value.
  <p>
  You MUST call {@link #writePayload(byte[])} or {@link #addPayload(byte[])} method to write body binary.
  
  @param len number of bytes of a binary to be written
  @return this
  @throws IOException when underlying output throws IOException