In looking at URL safe base 64 encoding, I've found it to be a very non-standard thing. Despite the copious number of built in functions that PHP has, there isn't one for URL safe base 64 encoding. On the manual page for [base64_encode()][1], most of the comments suggest using that function, wrapped with strtr():
function base64_url_encode($input)
{
return strtr(base64_encode($input), '+/=', '-_,');
}
The only Perl module I could find in this area is MIME::Base64::URLSafe (source), which performs the following replacement internally:
sub encode ($) {
my $data = encode_base64($_[0], '');
$data =~ tr|+/=|\-_|d;
return $data;
}
Unlike the PHP function above, this Perl version drops the '=' (equals) character entirely, rather than replacing it with ',' (comma). Equals is a padding character, so the Perl module replaces them as needed upon decode, but this difference makes the two implementations incompatible.
Finally, the Python function urlsafe_b64encode(s) keeps the '=' padding around, prompting someone to put up this function which shows prominently in Google results for 'python base64 url safe':
from base64 import urlsafe_b64encode, urlsafe_b64decode
def uri_b64encode(s):
return urlsafe_b64encode(s).strip('=')
def uri_b64decode(s):
return urlsafe_b64decode(s + '=' * (4 - len(s) % 4))
Since there isn't a defined standard, what is the right way?