migrate code for github

vendor/github.com/miekg/dns/dnsutil/util.go

@@ -0,0 +1,79 @@
+// Package dnsutil contains higher-level methods useful with the dns
+// package.  While package dns implements the DNS protocols itself,
+// these functions are related but not directly required for protocol
+// processing.  They are often useful in preparing input/output of the
+// functions in package dns.
+package dnsutil
+
+import (
+	"strings"
+
+	"github.com/miekg/dns"
+)
+
+// AddDomain adds origin to s if s is not already a FQDN.
+// Note that the result may not be a FQDN.  If origin does not end
+// with a ".", the result won't either.
+// This implements the zonefile convention (specified in RFC 1035,
+// Section "5.1. Format") that "@" represents the
+// apex (bare) domain. i.e. AddOrigin("@", "foo.com.") returns "foo.com.".
+func AddOrigin(s, origin string) string {
+	// ("foo.", "origin.") -> "foo." (already a FQDN)
+	// ("foo", "origin.") -> "foo.origin."
+	// ("foo"), "origin" -> "foo.origin"
+	// ("@", "origin.") -> "origin." (@ represents the apex (bare) domain)
+	// ("", "origin.") -> "origin." (not obvious)
+	// ("foo", "") -> "foo" (not obvious)
+
+	if dns.IsFqdn(s) {
+		return s // s is already a FQDN, no need to mess with it.
+	}
+	if len(origin) == 0 {
+		return s // Nothing to append.
+	}
+	if s == "@" || len(s) == 0 {
+		return origin // Expand apex.
+	}
+
+	if origin == "." {
+		return s + origin // AddOrigin(s, ".") is an expensive way to add a ".".
+	}
+
+	return s + "." + origin // The simple case.
+}
+
+// TrimDomainName trims origin from s if s is a subdomain.
+// This function will never return "", but returns "@" instead (@ represents the apex (bare) domain).
+func TrimDomainName(s, origin string) string {
+	// An apex (bare) domain is always returned as "@".
+	// If the return value ends in a ".", the domain was not the suffix.
+	// origin can end in "." or not. Either way the results should be the same.
+
+	if len(s) == 0 {
+		return "@" // Return the apex (@) rather than "".
+	}
+	// Someone is using TrimDomainName(s, ".") to remove a dot if it exists.
+	if origin == "." {
+		return strings.TrimSuffix(s, origin)
+	}
+
+	// Dude, you aren't even if the right subdomain!
+	if !dns.IsSubDomain(origin, s) {
+		return s
+	}
+
+	slabels := dns.Split(s)
+	olabels := dns.Split(origin)
+	m := dns.CompareDomainName(s, origin)
+	if len(olabels) == m {
+		if len(olabels) == len(slabels) {
+			return "@" // origin == s
+		}
+		if (s[0] == '.') && (len(slabels) == (len(olabels) + 1)) {
+			return "@" // TrimDomainName(".foo.", "foo.")
+		}
+	}
+
+	// Return the first (len-m) labels:
+	return s[:slabels[len(slabels)-m]-1]
+}