go/src/mime/grammar.go

// isTSpecial reports whether rune is in 'tspecials' as defined by RFC
// 1521 and RFC 2045.
func isTSpecial(r rune) bool { … }

// isTokenChar reports whether rune is in 'token' as defined by RFC
// 1521 and RFC 2045.
func isTokenChar(r rune) bool { … }

// isToken reports whether s is a 'token' as defined by RFC 1521
// and RFC 2045.
func isToken(s string) bool { … }