private boolean processSpecialTag() throws IOException {
        stream.mark(2);
        if (read() == TAG_START && contains(SPECIAL_TAGS, read())) {
            skipUntil(TAG_END);
            return true;
        }
        stream.reset();
        return false;
    }
A scanner meant to detect charset meta tags in a byte stream
See: https://html.spec.whatwg.org/multipage/parsing.html#prescan-a-byte-stream-to-determine-its-encoding
tika-parsers/tika-parsers-standard/tika-parsers-standard-modules/tika-parser-html-module/src/main/java/org/apache/tika/parser/html/charsetdetector/PreScanner.java