16進数、バイナリ、base64の相互変換をCLIとGo(Golang)でやる

要はこれをやるのだ（相互変換）

hexadecimal
 ↓       ↑
  binary
 ↓       ↑
  base64

CLIでやる

まず 16進数 to base64

echo "0123456789abcdef" | xxd -r -p | base64 # ASNFZ4mrze8=

base64 to 16進数

echo "ASNFZ4mrze8=" | base64 -d | hexdump # 0000000 01 23 45 67 89 ab cd ef

Golangでやる

package main

import (
    "encoding/base64"
    "encoding/hex"
    "fmt"
)

func main() {
    hexStr := "0123456789abcdef"

    // hexadecimal string -> byte -> base64 string
    b64Str, _ := hexToBase64(hexStr) // ASNFZ4mrze8=
    fmt.Printf("hex string -> byte -> base64 string: %s\n", b64Str)

    // base64 string -> byte -> hexadecimal string
    hexStr, _ = base64ToHex(b64Str) // 0123456789abcdef
    fmt.Printf("base64 string -> byte -> hex string: %s\n", hexStr)
}

func hexToBase64(in string) (out string, err error) {
    hexStr, err := hex.DecodeString(in)
    out = base64.StdEncoding.EncodeToString(hexStr)
    return
}

func base64ToHex(in string) (out string, err error) {
    b64Str, err := base64.StdEncoding.DecodeString(in)
    out = hex.EncodeToString(b64Str)
    return
}

結果

hex string -> byte -> base64 string: ASNFZ4mrze8=
base64 string -> byte -> hex string: 0123456789abcdef