67 lines
1.6 KiB
Go
67 lines
1.6 KiB
Go
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package updateip
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import (
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"strings"
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"unicode/utf8"
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)
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// CompressLabel returns the smallest possible subdomain label for the provided record against the domain.
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func CompressLabel(domainName, recordName string) string {
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domainName = UnFqdn(domainName)
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recordName = UnFqdn(recordName)
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if strings.EqualFold(domainName, recordName) {
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return "@"
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} else if i := indexFold(recordName, "."+domainName); i > -1 {
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return recordName[:i]
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}
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return recordName
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}
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// ExapandLabel gives the full DNS label for the (abbreviated) record.
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func ExapandLabel(domainName, recordName string) string {
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if strings.EqualFold(domainName, recordName) {
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return recordName
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} else if IsFqdn(recordName) {
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return recordName
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} else if recordName == "@" {
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return domainName
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} else if i := strings.LastIndex(recordName, ".@"); i > -1 {
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return recordName[:i] + "." + domainName
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}
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return recordName + "." + domainName
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}
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// indexFold returns the index of the first instance of substr in s (case insensitive), or -1 if substr is not present in s.
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func indexFold(s, substr string) int {
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ns := len(s)
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nb := len(substr)
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if ns < nb {
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return -1
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}
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if nb == 0 {
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return 0
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}
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if ns == nb {
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if strings.EqualFold(s, substr) {
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return 0
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}
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return -1
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}
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l := ns - nb
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for i := 0; i <= l; {
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src := s[i : i+nb]
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if strings.EqualFold(src, substr) {
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return i
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}
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_, z := utf8.DecodeRuneInString(src)
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i += z
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}
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return -1
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}
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// hasSuffixFold Tests if the string s ends with the specified suffix (case insensitive).
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func hasSuffixFold(s, suffix string) bool {
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return len(s) >= len(suffix) && strings.EqualFold(s[len(s)-len(suffix):], suffix)
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}
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