Convert EUI64 to EUI48 or MacAddress

Question

I am trying to convert EUI64 to EUI48 using goLang, but I don't seem to find any straight forward solution. Could anyone please help me with this.

Answer 1

You have to clear bytes in the middle (0xfffe) and toggle the 7th most significant bit:

package main

import (
    "fmt"
    "strconv"
    "regexp"
)

func main() {
   var eui64 string = "0221.86ff.feb5.6e10"
   fmt.Printf("%s\n", eui64)
   var eui48 string = from_eui_64_to_48(eui64)
   fmt.Printf("%s\n",eui48)
}

func from_eui_64_to_48(s string) string {
    reg, err := regexp.Compile("[^a-fA-F0-9]+") // keep only hex characters
    if err != nil {
        panic(err)
    }
    hexString := reg.ReplaceAllString(s, "")
    n, err := strconv.ParseInt(hexString, 16, 64) // convert string to int64
    if err != nil {
        panic(err)
    }
    n ^= 0x0200000000000000 // toggle the 7th most significant bit of 64 bits integer
    n = (n >> 12) | (n & 0xffffff) // keep 3 bytes from the left and 3 bytes from the right, clear 0xfffe

    return fmt.Sprintf("%012x",n) // return string
}

input:

0221.86ff.feb5.6e10

output:

02186fffef56