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utils.go
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/
utils.go
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package rfc9401
import (
"bytes"
"encoding/binary"
"fmt"
"math/rand"
"strconv"
"strings"
"time"
)
func uint16ToByte(i uint16) []byte {
b := make([]byte, 2)
binary.BigEndian.PutUint16(b, i)
return b
}
func uint32ToByte(i uint32) []byte {
b := make([]byte, 4)
binary.BigEndian.PutUint32(b, i)
return b
}
func byteToUint16(b []byte) uint16 {
return binary.BigEndian.Uint16(b)
}
func byteToUint32(b []byte) uint32 {
return binary.BigEndian.Uint32(b)
}
func sumByteArr(packet []byte) (sum uint) {
for i, _ := range packet {
if i%2 == 0 {
sum += uint(byteToUint16(packet[i:]))
}
}
return sum
}
func calcChecksum(packet []byte) []byte {
// まず16ビット毎に足す
sum := sumByteArr(packet)
// あふれた桁を足す
sum = (sum & 0xffff) + sum>>16
// 論理否定を取った値をbyteにして返す
return uint16ToByte(uint16(sum ^ 0xffff))
}
func addAckNumber(ack []byte, add uint32) []byte {
intack := byteToUint32(ack)
intack += add
return uint32ToByte(intack)
}
func ipv4ToByte(ipv4 string) []byte {
var b bytes.Buffer
str := strings.Split(ipv4, ".")
for _, v := range str {
i, _ := strconv.Atoi(v)
b.Write([]byte{byte(i)})
}
return b.Bytes()
}
func ipv4ByteToString(ipv4 []byte) string {
return fmt.Sprintf("%d.%d.%d.%d", ipv4[0], ipv4[1], ipv4[2], ipv4[3])
}
func getRandomClientPort() int {
rand.Seed(time.Now().UnixNano())
min := 30000
max := 60000
return rand.Intn(max-min+1) + min
}