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