Go Language

How to Encode - Decode Base64 String/URL in Golang

There are several methods that can be used to encode and decode data, and in this post we will study them.

#gopher lover. Anything in golang

Published · Nov 10 2019

  
Go has a package encoding/base64, containing functions for encoding and decoding data to base64 and vice versa. The data to be encoded must be of type []byte, casting needs to be performed for data that is not yet in its type.

There are several methods that can be used to encode and decode data, and in this chapter we will study them.
. . .
EncodeToString() & DecodeString()
The function is EncodeToString()used to encode data from string form to base46. The function DecodeString()performs the opposite of EncodeToString(). 

The following is an example of its application.
package main

import (
	"encoding/base64"
	"fmt"
)

func main() {
	var data = "john wick"

	var encodedString = base64.StdEncoding.EncodeToString([]byte(data))
	fmt.Println("encoded:", encodedString)

	var decodedByte, _ = base64.StdEncoding.DecodeString(encodedString)
	var decodedString = string(decodedByte)
	fmt.Println("decoded:", decodedString)
}

https://play.golang.org/p/DyMQ3Ma3HKT

Variables dataof type stringmust first be cast into the form []bytebefore being encoded using functions base64.StdEncoding.EncodeToString(). The result of encoding is data base64 type string.

Whereas in the decode function base64.StdEncoding.DecodeString(), base64 data of type is stringdecoded back to the original string, but of type []byte. The expression turns the string(decodedByte)data []byteinto a string.

#Output
encoded: am9obiB3aWNr
decoded: john wick
. . .
Encode() & Decode()
Both of these functions are the same as the functions we discussed earlier, one of the difference is the data to be converted and the results are of type []byte. 

The use of this method is quite long because the encoding or decode storage variables must be prepared in advance, and must have a width of data in accordance with the results to be accommodated (the value of which can be searched using the function EncodedLen()and DecodedLen()).

For more details, please consider the following example.
package main

import (
	"encoding/base64"
	"fmt"
)

func main() {
	var data = "john wick"

	var encoded = make([]byte, base64.StdEncoding.EncodedLen(len(data)))
	base64.StdEncoding.Encode(encoded, []byte(data))
	var encodedString = string(encoded)
	fmt.Println(encodedString)

	var decoded = make([]byte, base64.StdEncoding.DecodedLen(len(encoded)))
	var _, err = base64.StdEncoding.Decode(decoded, encoded)
	if err != nil {
		fmt.Println(err.Error())
	}
	var decodedString = string(decoded)
	fmt.Println(decodedString)
}

https://play.golang.org/p/JWfgvQqZKFx

The function base64.StdEncoding.EncodedLen(len(data))generates encoded data width information. The value is then determined as the width of the type allocation []byteon the variable encodedwhich will be used to hold the encoding results.

The function base64.StdEncoding.DecodedLen()has the same purpose as EncodedLen(), it's just used for decoding purposes.

Compared to the previous 2 functions, functions Encode()and Decode()have some differences. In addition to the width of the encode / decode container data must be sought first, there are other differences, namely in this function the results of the encode / decode are not obtained from the return value, but rather from the parameters. Variables used to store results are inserted in the parameters of the function.

In calling the encode / decode function, the variable encodedand decodedthe pointer value are not inserted, simply pass in the normal way, the data type is already in the form []byte.

#output
am9obiB3aWNr
john wick
. . .
Encode & Decode Data URL
Specifically encoding data strings whose contents are URLs, more effective use URLEncodingthan StdEncoding.

How to apply it is more or less the same, can use the first method and the second method that has been discussed above. Just change it StdEncodingto URLEncoding.
package main

import (
	"encoding/base64"
	"fmt"
)

func main() {
	var data = "http://depeloper.com/"

	var encodedString = base64.URLEncoding.EncodeToString([]byte(data))
	fmt.Println(encodedString)

	var decodedByte, _ = base64.URLEncoding.DecodeString(encodedString)
	var decodedString = string(decodedByte)

	fmt.Println(decodedString)
}

https://play.golang.org/p/5RFZe8Y6H2B

#Output 
aHR0cDovL2RlcGVsb3Blci5jb20v
http://depeloper.com/