docs: private void prefetchASCIIEncodingDecl() throws SAXException, IOException {
          int ch;
          readBufferPos = readBufferLength = 0;
  
          is.mark(readBuffer.length);
          while (true) {
              ch = is.read();
              readBuffer[readBufferLength++] = (char) ch;
              switch (ch) {
                  case '>':
                      return;
                  case -1:
                      fatal(
                              "file ends before end of XML or encoding declaration.",
                              null, "?>");
              }
              if (readBuffer.length == readBufferLength) {
                  fatal("unfinished XML or encoding declaration");
              }
          }
      }