coredns/plugin/file/tree/less.go
LongKB c8ba2d3ca8 Replacing 'HTTP' by 'HTTPS' for securing links (#2591)
Currently, there are some links that we access with **HTTP**, it is
redirected to **HTTPS** automatically. So this commit aims to
replace **http://...** by **https://...** for security.

Co-Authored-By: Nguyen Phuong An <AnNP@vn.fujitsu.com>
Signed-off-by: Kim Bao Long <longkb@vn.fujitsu.com>
2019-02-21 07:21:25 +00:00

59 lines
1.3 KiB
Go

package tree
import (
"bytes"
"github.com/miekg/dns"
)
// less returns <0 when a is less than b, 0 when they are equal and
// >0 when a is larger than b.
// The function orders names in DNSSEC canonical order: RFC 4034s section-6.1
//
// See https://bert-hubert.blogspot.co.uk/2015/10/how-to-do-fast-canonical-ordering-of.html
// for a blog article on this implementation, although here we still go label by label.
//
// The values of a and b are *not* lowercased before the comparison!
func less(a, b string) int {
i := 1
aj := len(a)
bj := len(b)
for {
ai, oka := dns.PrevLabel(a, i)
bi, okb := dns.PrevLabel(b, i)
if oka && okb {
return 0
}
// sadly this []byte will allocate... TODO(miek): check if this is needed
// for a name, otherwise compare the strings.
ab := []byte(a[ai:aj])
bb := []byte(b[bi:bj])
doDDD(ab)
doDDD(bb)
res := bytes.Compare(ab, bb)
if res != 0 {
return res
}
i++
aj, bj = ai, bi
}
}
func doDDD(b []byte) {
lb := len(b)
for i := 0; i < lb; i++ {
if i+3 < lb && b[i] == '\\' && isDigit(b[i+1]) && isDigit(b[i+2]) && isDigit(b[i+3]) {
b[i] = dddToByte(b[i:])
for j := i + 1; j < lb-3; j++ {
b[j] = b[j+3]
}
lb -= 3
}
}
}
func isDigit(b byte) bool { return b >= '0' && b <= '9' }
func dddToByte(s []byte) byte { return (s[1]-'0')*100 + (s[2]-'0')*10 + (s[3] - '0') }