code: private int getSeparatorIndex(ByteBuffer buf) {
          int colon = BufferUtils.indexOf(buf, (byte) ':');
          if (colon == -1) {
              throw new IllegalStateException("Unknown encoding format: " + ByteBufferUtil.bytesToHex(buf));
          }
          return colon;
      }
docs: Returns the index of the colon that separates the encoding prefix from the body suffix.