mirror of
https://github.com/soypat/lneto.git
synced 2026-07-26 10:38:47 +00:00
Marvin Drees
65 lines
1.5 KiB
Go
65 lines
1.5 KiB
Go
package ipv6
|
|
|
|
import "github.com/soypat/lneto/ipv4"
|
|
|
|
const (
|
|
sizeHeader = 40
|
|
)
|
|
|
|
type ToS = ipv4.ToS
|
|
|
|
// AppendFormatAddr appends the canonical text representation of an IPv6 address
|
|
// to dst following RFC 5952 conventions (lowercase hex, :: compression for the
|
|
// longest run of consecutive zero groups of length ≥ 2). Zero heap allocations.
|
|
func AppendFormatAddr(dst []byte, addr [16]byte) []byte {
|
|
const hexDigits = "0123456789abcdef"
|
|
|
|
// Find the longest run of consecutive all-zero 16-bit groups for :: compression.
|
|
bestStart, bestLen := 0, 0
|
|
curStart := -1
|
|
for i := range 8 {
|
|
if addr[i*2] == 0 && addr[i*2+1] == 0 {
|
|
if curStart < 0 {
|
|
curStart = i
|
|
}
|
|
if i-curStart+1 > bestLen {
|
|
bestStart = curStart
|
|
bestLen = i - curStart + 1
|
|
}
|
|
} else {
|
|
curStart = -1
|
|
}
|
|
}
|
|
if bestLen < 2 {
|
|
bestLen = 0 // RFC 5952 §4.2.2: do not compress a single 16-bit group.
|
|
}
|
|
|
|
needColon := false
|
|
for i := 0; i < 8; i++ {
|
|
if bestLen > 0 && i == bestStart {
|
|
dst = append(dst, ':', ':')
|
|
i += bestLen - 1 // skip compressed groups; loop increments i.
|
|
needColon = false
|
|
continue
|
|
}
|
|
if needColon {
|
|
dst = append(dst, ':')
|
|
}
|
|
needColon = true
|
|
hi := addr[i*2]
|
|
lo := addr[i*2+1]
|
|
v := uint16(hi)<<8 | uint16(lo)
|
|
if v >= 0x1000 {
|
|
dst = append(dst, hexDigits[hi>>4])
|
|
}
|
|
if v >= 0x100 {
|
|
dst = append(dst, hexDigits[hi&0xf])
|
|
}
|
|
if v >= 0x10 {
|
|
dst = append(dst, hexDigits[lo>>4])
|
|
}
|
|
dst = append(dst, hexDigits[lo&0xf])
|
|
}
|
|
return dst
|
|
}
|