func extractACMeta(r io.Reader) []acMeta {
var meta []acMeta
z := html.NewTokenizer(r)
for {
switch z.Next() {
case html.ErrorToken:
return meta
case html.StartTagToken, html.SelfClosingTagToken:
tok := z.Token()
if tok.DataAtom == atom.Meta {
meta = appendMeta(meta, tok.Attr)
}
}
}
}
func prescan(content []byte) (e encoding.Encoding, name string) {
z := html.NewTokenizer(bytes.NewReader(content))
for {
switch z.Next() {
case html.ErrorToken:
return nil, ""
case html.StartTagToken, html.SelfClosingTagToken:
tagName, hasAttr := z.TagName()
if !bytes.Equal(tagName, []byte("meta")) {
continue
}
attrList := make(map[string]bool)
gotPragma := false
const (
dontKnow = iota
doNeedPragma
doNotNeedPragma
)
needPragma := dontKnow
name = ""
e = nil
for hasAttr {
var key, val []byte
key, val, hasAttr = z.TagAttr()
ks := string(key)
if attrList[ks] {
continue
}
attrList[ks] = true
for i, c := range val {
if 'A' <= c && c <= 'Z' {
val[i] = c + 0x20
}
}
switch ks {
case "http-equiv":
if bytes.Equal(val, []byte("content-type")) {
gotPragma = true
}
case "content":
if e == nil {
name = fromMetaElement(string(val))
if name != "" {
e, name = Lookup(name)
if e != nil {
needPragma = doNeedPragma
}
}
}
case "charset":
e, name = Lookup(string(val))
needPragma = doNotNeedPragma
}
}
if needPragma == dontKnow || needPragma == doNeedPragma && !gotPragma {
continue
}
if strings.HasPrefix(name, "utf-16") {
name = "utf-8"
e = encoding.Nop
}
if e != nil {
return e, name
}
}
}
}