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package nl
import "encoding/binary"
const (
MPLS_LS_LABEL_SHIFT = 12
MPLS_LS_S_SHIFT = 8
)
func EncodeMPLSStack(labels ...int) []byte {
b := make([]byte, 4*len(labels))
for idx, label := range labels {
l := label << MPLS_LS_LABEL_SHIFT
if idx == len(labels)-1 {
l |= 1 << MPLS_LS_S_SHIFT
}
binary.BigEndian.PutUint32(b[idx*4:], uint32(l))
}
return b
}
func DecodeMPLSStack(buf []byte) []int {
if len(buf)%4 != 0 {
return nil
}
stack := make([]int, 0, len(buf)/4)
for len(buf) > 0 {
l := binary.BigEndian.Uint32(buf[:4])
buf = buf[4:]
stack = append(stack, int(l)>>MPLS_LS_LABEL_SHIFT)
if (l>>MPLS_LS_S_SHIFT)&1 > 0 {
break
}
}
return stack
}
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