code: private static Integer legalCharacter(final Opt<Integer> data,
          final ByteArrayOutputStream baos, final Integer position)
          throws HttpException {
          // @checkstyle MagicNumber (1 line)
          if ((data.get() > 0x7f || data.get() < 0x20)
              && data.get() != '\t') {
              throw new HttpException(
                  HttpURLConnection.HTTP_BAD_REQUEST,
                  String.format(
                      "illegal character 0x%02X in HTTP header line #%d: \"%s\"",
                      data.get(),
                      position,
                      new Utf8String(baos.toByteArray()).asString()
                  )
              );
          }
          return data.get();
      }
docs: Returns a legal character based n the read character.
  @param data Character read
  @param baos Byte stream containing read header
  @param position Header line number
  @return A legal character
  @throws HttpException if character is illegal