TTuck
Encoding · Example 61

Base64 Encoding

encoding/base64 encoding/hex fmt

Go provides built-in support for base64 encoding and decoding, and for hex encoding in encoding/hex.

package main

import (
	b64 "encoding/base64"
	"encoding/hex"
	"fmt"
)

This syntax imports the encoding/base64 package with the b64 name instead of the default base64. It'll save us some space below.

func main() {

Here's the string we'll encode/decode.

	data := "abc123!?$*&()'-=@~"

Go supports both standard and URL-compatible base64. Here's how to encode using the standard encoder. The encoder requires a []byte so we convert our string to that type.

	sEnc := b64.StdEncoding.EncodeToString([]byte(data))
	fmt.Println(sEnc)

Decoding may return an error, which you can check if you don't already know the input to be well-formed.

	sDec, _ := b64.StdEncoding.DecodeString(sEnc)
	fmt.Println(string(sDec))
	fmt.Println()

This encodes/decodes using a URL-compatible base64 format.

	uEnc := b64.URLEncoding.EncodeToString([]byte(data))
	fmt.Println(uEnc)
	uDec, _ := b64.URLEncoding.DecodeString(uEnc)
	fmt.Println(string(uDec))

The string encodes to slightly different values with the standard and URL base64 encoders (trailing + vs -) but they both decode to the original string as desired. RawURLEncoding also drops the = padding, as JWTs do.

	fmt.Println(b64.RawURLEncoding.EncodeToString([]byte("hi")))

Invalid input is reported as an error.

	_, err := b64.StdEncoding.DecodeString("not base64!")
	fmt.Println("error:", err)

Hex encoding writes two characters per byte.

	h := hex.EncodeToString([]byte("Go"))
	back, _ := hex.DecodeString(h)
	fmt.Println(h, string(back))
}
$ go run ./61_base64_encoding
YWJjMTIzIT8kKiYoKSctPUB+
abc123!?$*&()'-=@~

YWJjMTIzIT8kKiYoKSctPUB-
abc123!?$*&()'-=@~
aGk
error: illegal base64 data at input byte 3
476f Go
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