Constant time hex and base64, encode and decode.

Base64 encoding with these character sets:

• "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" base64Encode() and base64Decode()
• "./ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789" base64EncodeDotSlash() and base64DecodeDotSlash()
• "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" base64EncodeDotSlashOrdered() and base64DecodeDotSlashOrdered()

It looks correct there are some tests but there might be bugs.

I'm pretty sure there are problems with PHP and multi-byte character strings. I think it's something screwy with strlen() and maybe ord() and chr(). So you should probably not use this yet.