registry/vendor/github.com/miekg/dns/labels.go
Derek McGowan a685e3fc98
Replace godep with vndr
Vndr has a simpler configuration and allows pointing to forked
packages. Additionally other docker projects are now using
vndr making vendoring in distribution more consistent.

Updates letsencrypt to use fork.
No longer uses sub-vendored packages.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)
2016-11-23 15:07:06 -08:00

168 lines
3.6 KiB
Go

package dns
// Holds a bunch of helper functions for dealing with labels.
// SplitDomainName splits a name string into it's labels.
// www.miek.nl. returns []string{"www", "miek", "nl"}
// .www.miek.nl. returns []string{"", "www", "miek", "nl"},
// The root label (.) returns nil. Note that using
// strings.Split(s) will work in most cases, but does not handle
// escaped dots (\.) for instance.
// s must be a syntactically valid domain name, see IsDomainName.
func SplitDomainName(s string) (labels []string) {
if len(s) == 0 {
return nil
}
fqdnEnd := 0 // offset of the final '.' or the length of the name
idx := Split(s)
begin := 0
if s[len(s)-1] == '.' {
fqdnEnd = len(s) - 1
} else {
fqdnEnd = len(s)
}
switch len(idx) {
case 0:
return nil
case 1:
// no-op
default:
end := 0
for i := 1; i < len(idx); i++ {
end = idx[i]
labels = append(labels, s[begin:end-1])
begin = end
}
}
labels = append(labels, s[begin:fqdnEnd])
return labels
}
// CompareDomainName compares the names s1 and s2 and
// returns how many labels they have in common starting from the *right*.
// The comparison stops at the first inequality. The names are not downcased
// before the comparison.
//
// www.miek.nl. and miek.nl. have two labels in common: miek and nl
// www.miek.nl. and www.bla.nl. have one label in common: nl
//
// s1 and s2 must be syntactically valid domain names.
func CompareDomainName(s1, s2 string) (n int) {
s1 = Fqdn(s1)
s2 = Fqdn(s2)
l1 := Split(s1)
l2 := Split(s2)
// the first check: root label
if l1 == nil || l2 == nil {
return
}
j1 := len(l1) - 1 // end
i1 := len(l1) - 2 // start
j2 := len(l2) - 1
i2 := len(l2) - 2
// the second check can be done here: last/only label
// before we fall through into the for-loop below
if s1[l1[j1]:] == s2[l2[j2]:] {
n++
} else {
return
}
for {
if i1 < 0 || i2 < 0 {
break
}
if s1[l1[i1]:l1[j1]] == s2[l2[i2]:l2[j2]] {
n++
} else {
break
}
j1--
i1--
j2--
i2--
}
return
}
// CountLabel counts the the number of labels in the string s.
// s must be a syntactically valid domain name.
func CountLabel(s string) (labels int) {
if s == "." {
return
}
off := 0
end := false
for {
off, end = NextLabel(s, off)
labels++
if end {
return
}
}
}
// Split splits a name s into its label indexes.
// www.miek.nl. returns []int{0, 4, 9}, www.miek.nl also returns []int{0, 4, 9}.
// The root name (.) returns nil. Also see SplitDomainName.
// s must be a syntactically valid domain name.
func Split(s string) []int {
if s == "." {
return nil
}
idx := make([]int, 1, 3)
off := 0
end := false
for {
off, end = NextLabel(s, off)
if end {
return idx
}
idx = append(idx, off)
}
}
// NextLabel returns the index of the start of the next label in the
// string s starting at offset.
// The bool end is true when the end of the string has been reached.
// Also see PrevLabel.
func NextLabel(s string, offset int) (i int, end bool) {
quote := false
for i = offset; i < len(s)-1; i++ {
switch s[i] {
case '\\':
quote = !quote
default:
quote = false
case '.':
if quote {
quote = !quote
continue
}
return i + 1, false
}
}
return i + 1, true
}
// PrevLabel returns the index of the label when starting from the right and
// jumping n labels to the left.
// The bool start is true when the start of the string has been overshot.
// Also see NextLabel.
func PrevLabel(s string, n int) (i int, start bool) {
if n == 0 {
return len(s), false
}
lab := Split(s)
if lab == nil {
return 0, true
}
if n > len(lab) {
return 0, true
}
return lab[len(lab)-n], false
}