Golang Base64 Encoding and Decoding

Introduction

Base64 is a standard encoding for converting binary data to text format. Base64 is commonly used for encoding binary data in text formats such as JSON, XML, and HTML. Base64 is also used for encoding binary data in email attachments.

Base64 Encoding in Go

Encoding is the process of converting data from one format to another. In this case, we are converting binary data to text. The base64 package provides the EncodeToString function for encoding binary data to base64.

package main

import (
    "encoding/base64"
    "fmt"
)

func main(){
    data := []byte("Hello World!")
    encoded := base64.StdEncoding.EncodeToString(data)
    fmt.Println(encoded)
}

The EncodeToString function takes a byte slice as input and returns a string. The StdEncoding variable is a *Encoding type that implements the Encoding interface. The Encoding interface provides the EncodeToString function.

The output of the program is:

SGVsbG8gV29ybGQh

Base64 Decoding in Go

Decoding is the process of converting data from one format to another. In this case, we are converting text to binary data. The base64 package provides the DecodeString function for decoding base64 to binary data.

package main

import (
    "encoding/base64"
    "fmt"
)

func main(){
    data := []byte("SGVsbG8gV29ybGQh")
    decoded, err := base64.StdEncoding.DecodeString(string(data))
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println(string(decoded))
}

The DecodeString function takes a string as input and returns a byte slice. The StdEncoding variable is a *Encoding type that implements the Encoding interface. The Encoding interface provides the DecodeString function.

The output of the program is:

Hello World!

Url Encoding and Decoding

The base64 package provides the URLEncoding variable for encoding and decoding base64 using the URL and filename safe alphabet. The URLEncoding variable is a *Encoding type that implements the Encoding interface. The Encoding interface provides the EncodeToString and DecodeString functions.

package main

import (
    "encoding/base64"
    "fmt"
)

func main(){
    data := []byte("Hello World!")
    encoded := base64.URLEncoding.EncodeToString(data)
    fmt.Println(encoded)
    decoded, err := base64.URLEncoding.DecodeString(encoded)
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println(string(decoded))
}

This program functions the same as the previous program but uses the URLEncoding variable instead of the StdEncoding variable.

The output of the program is:

SGVsbG8gV29ybGQh
Hello World!

Raw Encoding and Decoding

The base64 package provides the RawStdEncoding variable for encoding and decoding base64 using the standard raw, unpadded base64 format. The RawStdEncoding variable is a *Encoding type that implements the Encoding interface. The Encoding interface provides the EncodeToString and DecodeString functions.

package main

import (
    "encoding/base64"
    "fmt"
)

func main(){
    data := []byte("Hello World!")
    encoded := base64.RawStdEncoding.EncodeToString(data)
    fmt.Println(encoded)
    decoded, err := base64.RawStdEncoding.DecodeString(encoded)
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println(string(decoded))
}

Raw encoding and decoding are useful when encoding binary data that needs to be stored in a text format. The output of the program is:

SGVsbG8gV29ybGQh
Hello World!

Example: Encoding and Decoding a JSON Object

The base64 package provides the EncodeToString and DecodeString functions for encoding and decoding base64. The json package provides the Marshal and Unmarshal functions for encoding and decoding JSON. The json package also provides the MarshalIndent function for encoding JSON with indentation.

package main

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

type Person struct {
    Name string
    Age int
}

func main(){
    p := Person{
        Name: "John Doe",
        Age: 30,
    }
    data, err := json.MarshalIndent(p, "", "    ")
    if err != nil {
        fmt.Println(err)
    }
    encoded := base64.StdEncoding.EncodeToString(data)
    fmt.Println(encoded)
    decoded, err := base64.StdEncoding.DecodeString(encoded)
    if err != nil {
        fmt.Println(err)
    }
    var p2 Person
    err = json.Unmarshal(decoded, &p2)
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println(p2)
}

The MarshalIndent function takes a value and returns a byte slice. The MarshalIndent function also takes a prefix and an indent string. The prefix is prepended to each line of the output. The indent string is used to indent each level of the output. The MarshalIndent function is useful for encoding JSON with indentation.

The Unmarshal function takes a byte slice and a pointer to a value. The Unmarshal function decodes the JSON-encoded data and stores the result in the value pointed to by v. The Unmarshal function returns an error if the JSON-encoded data is not a valid representation of the value pointed to by v.

The output of the program is:

eyJBY2UiOjMwLCJOYW1lIjoiSm9obiBEb2UifQ==
{30 John Doe}

Other Functions in the Base64 Package

NewEncoder - returns a new base64 stream encoder. Writes to the returned writer encode base64 data to w.
NewDecoder - returns a new base64 stream decoder. Reads from r decode base64 data to w.
NewEncoding - returns a new custom Encoding defined by the given alphabet, which must be a 64-byte string that does not contain the padding character ’=’.
RawStdEncoding - returns the standard raw, unpadded base64 encoding.

Other Types in the Base64 Package

Encoding - represents a base64 encoding/decoding scheme, defined by a 64-character alphabet. The most common usage is via the standard predefined Encodings StdEncoding and URLEncoding.
CorruptInputError - an error that reports that the input is not valid base64 data.

Conclusion

In this article, we looked at how to encode and decode base64 in Go. We looked at the base64 package and the EncodeToString and DecodeString functions. We also looked at the URLEncoding and RawStdEncoding variables.

Subscribe to my newsletter

Get the latest posts delivered right to your inbox.