}

  // Test for common pitfall regarding sign extension.
  // For example: (long) data[i++] | (long) data[i++] << 8 | ...
  // If data[i] == (byte) 0x80, the first cast will sign-extend it to 0xffffffffffffff80,
  // masking the remaining seven bytes.
  // To test this, we give an input where bit 7 is not cleared. For example:
  // (1) 00 01 02 03 04 05 06 07 80
  // (2) 00 01 02 03 04 05 06 07 81

  }

  // Test for common pitfall regarding sign extension.
  // For example: (long) data[i++] | (long) data[i++] << 8 | ...
  // If data[i] == (byte) 0x80, the first cast will sign-extend it to 0xffffffffffffff80,
  // masking the remaining seven bytes.
  // To test this, we give an input where bit 7 is not cleared. For example:
  // (1) 00 01 02 03 04 05 06 07 80
  // (2) 00 01 02 03 04 05 06 07 81

    } else if (frameLength == PAYLOAD_LONG.toLong()) {
      frameLength = source.readLong()
      if (frameLength < 0L) {
        throw ProtocolException(
          "Frame length 0x${frameLength.toHexString()} > 0x7FFFFFFFFFFFFFFF",
        )
      }
    }

    if (isControlFrame && frameLength > PAYLOAD_BYTE_MAX) {
      throw ProtocolException("Control frame must be less than ${PAYLOAD_BYTE_MAX}B.")
    }