Base64 encode/decode without padding on golang ( appengine )

Question

There's a way to encode/decode a string to/from Base64 without having the padding at the end? I mean the '==' ending.

I'm using base64.URLEncoding.EncodeToString to encode and it works perfectly but I didn't see a way to decide to not use the padding at the end ( like on java ).

Answer 1

Go1.5 will have a WithPadding option on Encoding.

This also will add 2 pre-defined encodings, RawStdEncoding, and RawURLEncoding, which will have no padding.

Though since you're on app-engine, and won't have access to Go1.5 for a while, you can make some helper function to add and remove the padding as needed.

Here is an example to encode and decode strings. If you need, it could easily be adapted to work more efficiently using []byte.

func base64EncodeStripped(s string) string {
    encoded := base64.StdEncoding.EncodeToString([]byte(s))
    return strings.TrimRight(encoded, "=")
}

func base64DecodeStripped(s string) (string, error) {
    if i := len(s) % 4; i != 0 {
        s += strings.Repeat("=", 4-i)
    }
    decoded, err := base64.StdEncoding.DecodeString(s)
    return string(decoded), err
}

Answer 2

Simply,

use base64.RawStdEncoding.EncodeToString instead of base64.StdEncoding.EncodeToString

OR else

use base64.RawURLEncoding.EncodeToString instead of base64.URLEncoding.EncodeToString.

Reference: see source-code comments Line 94 to 110:

// RawURLEncoding is the unpadded alternate base64 encoding defined in RFC 4648.
// It is typically used in URLs and file names.
// This is the same as URLEncoding but omits padding characters.