1 package network
2
3 import (
4 "encoding/binary"
5 )
6
7 type header struct {
8 Checksum uint32
9 Ack uint8
10 AckReturn uint8
11 PacketType packettype_t
12 Reserved uint8
13 }
14
15 type checksumCalculator struct {
16 checksum uint32
17 term int
18 }
19
20 func newChecksumCalculator() *checksumCalculator {
21 return &checksumCalculator{0x1234567, 1}
22 }
23
24 func (c *checksumCalculator) Write(data []byte) (n int, err error) {
25 var skip = 0
26
27 if c.term == 1 {
28 skip = 4
29 }
30 for _, d := range data[skip:] {
31 c.checksum += uint32(d) * uint32(c.term)
32 c.term += 1
33 }
34 return len(data), nil
35 }
36
37 func (c *checksumCalculator) setChecksum(h *header, data any) {
38 err := binary.Write(c, binary.LittleEndian, h)
39 if err != nil {
40 panic(err)
41 }
42 err = binary.Write(c, binary.LittleEndian, data)
43 if err != nil {
44 panic(err)
45 }
46 h.Checksum = c.checksum
47 }
48
49 func makeHeader(packetType packettype_t, packetData any) header {
50 h := header{0, 0, 0, packetType, 0}
51 c := newChecksumCalculator()
52 c.setChecksum(&h, packetData)
53 return h
54 }
55
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