// ToPunycode converts unicode domain names to DNS-appropriate punycode names.
// This function will return an empty string result for domain names with
// invalid unicode strings. This function expects domain names in lowercase.
func ToPunycode(s string) string {
// Early check to see if encoding is needed.
// This will prevent making heap allocations when not needed.
if !needToPunycode(s) {
return s
}
tokens := dns.SplitDomainName(s)
switch {
case s == "":
return ""
case tokens == nil: // s == .
return "."
case s[len(s)-1] == '.':
tokens = append(tokens, "")
}
for i := range tokens {
t := encode([]byte(tokens[i]))
if t == nil {
return ""
}
tokens[i] = string(t)
}
return strings.Join(tokens, ".")
}
// FromPunycode returns unicode domain name from provided punycode string.
func FromPunycode(s string) string {
tokens := dns.SplitDomainName(s)
switch {
case s == "":
return ""
case tokens == nil: // s == .
return "."
case s[len(s)-1] == '.':
tokens = append(tokens, "")
}
for i := range tokens {
tokens[i] = string(decode([]byte(tokens[i])))
}
return strings.Join(tokens, ".")
}