dissertation-2-code/udp/packet.go

package udp

import (
	"encoding/binary"
	"mpbl3p/proxy"
	"mpbl3p/shared"
)

type Packet struct {
	ack  uint32
	nack uint32
	seq  uint32

	data proxy.Packet
}

func UnmarshalPacket(b []byte) (p Packet, err error) {
	if len(b) < 12 {
		return Packet{}, shared.ErrNotEnoughBytes
	}

	p.ack = binary.LittleEndian.Uint32(b[0:4])
	p.nack = binary.LittleEndian.Uint32(b[4:8])
	p.seq = binary.LittleEndian.Uint32(b[8:12])

	p.data = proxy.SimplePacket(b[12:])
	return p, nil
}

func (p Packet) Marshal() []byte {
	data := p.data.Marshal()
	header := make([]byte, 12)

	binary.LittleEndian.PutUint32(header[0:4], p.ack)
	binary.LittleEndian.PutUint32(header[4:8], p.nack)
	binary.LittleEndian.PutUint32(header[8:12], p.seq)

	return append(header, data...)
}

func (p Packet) Contents() []byte {
	return p.data.Contents()
}