Source: doctype.go in package golang.org/x/net/html


package html

import (
	"strings"
)

parseDoctype parses the data from a DoctypeToken into a name, public identifier, and system identifier. It returns a Node whose Type is DoctypeNode, whose Data is the name, and which has attributes named "system" and "public" for the two identifiers if they were present. quirks is whether the document should be parsed in "quirks mode".

func parseDoctype(s string) (n *Node, quirks bool) {
	n = &Node{Type: DoctypeNode}

Find the name.

	space := strings.IndexAny(s, whitespace)
	if space == -1 {
		space = len(s)
	}

The comparison to "html" is case-sensitive.

	if n.Data != "html" {
		quirks = true
	}
	n.Data = strings.ToLower(n.Data)
	s = strings.TrimLeft(s[space:], whitespace)

It can't start with "PUBLIC" or "SYSTEM". Ignore the rest of the string.

		return n, quirks || s != ""
	}

	key := strings.ToLower(s[:6])
	s = s[6:]
	for key == "public" || key == "system" {
		s = strings.TrimLeft(s, whitespace)
		if s == "" {
			break
		}
		quote := s[0]
		if quote != '"' && quote != '\'' {
			break
		}
		s = s[1:]
		q := strings.IndexRune(s, rune(quote))
		var id string
		if q == -1 {
			id = s
			s = ""
		} else {
			id = s[:q]
			s = s[q+1:]
		}
		n.Attr = append(n.Attr, Attribute{Key: key, Val: id})
		if key == "public" {
			key = "system"
		} else {
			key = ""
		}
	}

	if key != "" || s != "" {
		quirks = true
	} else if len(n.Attr) > 0 {
		if n.Attr[0].Key == "public" {
			public := strings.ToLower(n.Attr[0].Val)
			switch public {
			case "-//w3o//dtd w3 html strict 3.0//en//", "-/w3d/dtd html 4.0 transitional/en", "html":
				quirks = true
			default:
				for _, q := range quirkyIDs {
					if strings.HasPrefix(public, q) {
						quirks = true
						break
					}
				}

The following two public IDs only cause quirks mode if there is no system ID.

			if len(n.Attr) == 1 && (strings.HasPrefix(public, "-//w3c//dtd html 4.01 frameset//") ||
				strings.HasPrefix(public, "-//w3c//dtd html 4.01 transitional//")) {
				quirks = true
			}
		}
		if lastAttr := n.Attr[len(n.Attr)-1]; lastAttr.Key == "system" &&
			strings.ToLower(lastAttr.Val) == "http://www.ibm.com/data/dtd/v11/ibmxhtml1-transitional.dtd" {
			quirks = true
		}
	}

	return n, quirks
}

quirkyIDs is a list of public doctype identifiers that cause a document to be interpreted in quirks mode. The identifiers should be in lower case.

var quirkyIDs = []string{
	"+//silmaril//dtd html pro v0r11 19970101//",
	"-//advasoft ltd//dtd html 3.0 aswedit + extensions//",
	"-//as//dtd html 3.0 aswedit + extensions//",
	"-//ietf//dtd html 2.0 level 1//",
	"-//ietf//dtd html 2.0 level 2//",
	"-//ietf//dtd html 2.0 strict level 1//",
	"-//ietf//dtd html 2.0 strict level 2//",
	"-//ietf//dtd html 2.0 strict//",
	"-//ietf//dtd html 2.0//",
	"-//ietf//dtd html 2.1e//",
	"-//ietf//dtd html 3.0//",
	"-//ietf//dtd html 3.2 final//",
	"-//ietf//dtd html 3.2//",
	"-//ietf//dtd html 3//",
	"-//ietf//dtd html level 0//",
	"-//ietf//dtd html level 1//",
	"-//ietf//dtd html level 2//",
	"-//ietf//dtd html level 3//",
	"-//ietf//dtd html strict level 0//",
	"-//ietf//dtd html strict level 1//",
	"-//ietf//dtd html strict level 2//",
	"-//ietf//dtd html strict level 3//",
	"-//ietf//dtd html strict//",
	"-//ietf//dtd html//",
	"-//metrius//dtd metrius presentational//",
	"-//microsoft//dtd internet explorer 2.0 html strict//",
	"-//microsoft//dtd internet explorer 2.0 html//",
	"-//microsoft//dtd internet explorer 2.0 tables//",
	"-//microsoft//dtd internet explorer 3.0 html strict//",
	"-//microsoft//dtd internet explorer 3.0 html//",
	"-//microsoft//dtd internet explorer 3.0 tables//",
	"-//netscape comm. corp.//dtd html//",
	"-//netscape comm. corp.//dtd strict html//",
	"-//o'reilly and associates//dtd html 2.0//",
	"-//o'reilly and associates//dtd html extended 1.0//",
	"-//o'reilly and associates//dtd html extended relaxed 1.0//",
	"-//softquad software//dtd hotmetal pro 6.0::19990601::extensions to html 4.0//",
	"-//softquad//dtd hotmetal pro 4.0::19971010::extensions to html 4.0//",
	"-//spyglass//dtd html 2.0 extended//",
	"-//sq//dtd html 2.0 hotmetal + extensions//",
	"-//sun microsystems corp.//dtd hotjava html//",
	"-//sun microsystems corp.//dtd hotjava strict html//",
	"-//w3c//dtd html 3 1995-03-24//",
	"-//w3c//dtd html 3.2 draft//",
	"-//w3c//dtd html 3.2 final//",
	"-//w3c//dtd html 3.2//",
	"-//w3c//dtd html 3.2s draft//",
	"-//w3c//dtd html 4.0 frameset//",
	"-//w3c//dtd html 4.0 transitional//",
	"-//w3c//dtd html experimental 19960712//",
	"-//w3c//dtd html experimental 970421//",
	"-//w3c//dtd w3 html//",
	"-//w3o//dtd w3 html 3.0//",
	"-//webtechs//dtd mozilla html 2.0//",
	"-//webtechs//dtd mozilla html//",