base64 encode/decode safe for url and cookie

[benbro]

When using base64 strings in urls or http cookies we need to:

1. Remove "=" padding
2. Replace "+" with "-"
3. Replace "/" with "_"
   http://en.wikipedia.org/wiki/Base64#URL_applications

I've implemented encode_base64_url/1 and decode_base64_url/1 which return binary.
Will you consider adding it?

encode_base64_url(Url) ->
    Url1 = base64:encode(Url),
    Url2 = re:replace(Url1, <<"=+$">>, <<"">>, [{return, binary}]),
    Url3 = binary:replace(Url2, <<"/">>, <<"_">>, [global]),
    binary:replace(Url3, <<"+">>, <<"-">>, [global]).

decode_base64_url(Url64) when is_list(Url64) ->
    decode_base64_url(list_to_binary(Url64));

decode_base64_url(Url64) ->
    Url1 = binary:replace(Url64, <<"-">>, <<"+">>, [global]),
    Url2 = binary:replace(Url1, <<"_">>, <<"/">>, [global]),
    Padding = case byte_size(Url2) rem 4 of
        2 ->
            <<"==">>;
        3 ->
            <<"=">>;
        _ ->
            <<"">>
    end,
    base64:decode(<<Url2/binary, Padding/binary>>).

[dylanz]

+1 ... I'd like to see something like this added as well (I'm having to deal w/ base64 cookie values).

[KlausTrainer]

+1

[qihuaheng]

+1 it fix my problem, tks.

[etrepum]

Did you even look? This has been available since mochiweb 2.5.0 in the mochiweb_base64url module.