35 lines
756 B
Go
35 lines
756 B
Go
package dnsxl
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import (
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"net"
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"strconv"
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"strings"
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)
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// reverseName converts an IPv4 or IPv6 address into the reversed name
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// notation as described in RFC 1034 (for IPv4) or RFC 3596 (for IPv6).
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func reverseName(ip net.IP) string {
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const hexdig = "0123456789abcdef"
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var b strings.Builder
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if ip4 := ip.To4(); ip4 != nil {
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b.WriteString(strconv.Itoa(int(ip4[3])))
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b.WriteByte('.')
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b.WriteString(strconv.Itoa(int(ip4[2])))
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b.WriteByte('.')
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b.WriteString(strconv.Itoa(int(ip4[1])))
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b.WriteByte('.')
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b.WriteString(strconv.Itoa(int(ip4[0])))
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} else {
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for i := 15; i >= 0; i-- {
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x := ip[i]
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b.WriteByte(hexdig[x&15])
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b.WriteByte('.')
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b.WriteByte(hexdig[x>>4])
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if i > 0 {
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b.WriteByte('.')
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}
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}
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}
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return b.String()
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}
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