1 package nl
2
3 import "encoding/binary"
4
5 const (
6 MPLS_LS_LABEL_SHIFT = 12
7 MPLS_LS_S_SHIFT = 8
8 )
9
10 func EncodeMPLSStack(labels ...int) []byte {
11 b := make([]byte, 4*len(labels))
12 for idx, label := range labels {
13 l := label << MPLS_LS_LABEL_SHIFT
14 if idx == len(labels)-1 {
15 l |= 1 << MPLS_LS_S_SHIFT
16 }
17 binary.BigEndian.PutUint32(b[idx*4:], uint32(l))
18 }
19 return b
20 }
21
22 func DecodeMPLSStack(buf []byte) []int {
23 if len(buf)%4 != 0 {
24 return nil
25 }
26 stack := make([]int, 0, len(buf)/4)
27 for len(buf) > 0 {
28 l := binary.BigEndian.Uint32(buf[:4])
29 buf = buf[4:]
30 stack = append(stack, int(l)>>MPLS_LS_LABEL_SHIFT)
31 if (l>>MPLS_LS_S_SHIFT)&1 > 0 {
32 break
33 }
34 }
35 return stack
36 }
37
View as plain text