Convert binary data to and from UrlBase64 encoding. This is identical to Base64 encoding, except that the padding character is "." and the other non-alphanumeric characters are "-" and "_" instead of "+" and "/".

The purpose of UrlBase64 encoding is to provide a compact encoding of binary data that is safe for use as an URL parameter. Base64 encoding does not produce encoded values that are safe for use in URLs, since "/" can be interpreted as a path delimiter; "+" is the encoded form of a space; and "=" is used to separate a name from the corresponding value in an URL parameter.