About

Once in a while I needed to use a different style of Base64 encoding then provided by the .net framework via Convert.ToBase64String and Convert.FromBase64String. Currently there are two alternatives where the first are the other conversion methods Convert.ToBase64CharArray and Convert.FromBase64CharArray but these are still very inefficient when you need to combine them with character replacement pre/post-processing. The second is the use of FromBase64Transform and ToBase64Transform but both operate on streams and both don't support other Base64 encodings.

I started browsing for code and found the following two articles by Timm Martin and 'wchvic'

• http://www.csharp411.com/convert-binary-to-base64-string/
• http://www.codeproject.com/KB/cs/base64encdec.aspx

Both work and the version by Timm is faster but browsing the code made me think that it could be optimized even further.

I basically did the following optimalizations:

• Make use of readonly members resulting inlining references by the .net runtime
• Unsafe code to make the code more readable and efficient
• Removed the IF statement from the FOR loop as it was only used to do work in the last 'block'
• Tests refactored to an nunit fixture

Besides the performance enhancements I also added support for:

• Base64 encoding with or without padding characters.
• Base64 decoding accepting strings without padding characters.
• Support for a couple of 'standard' Base64 encoding methods like xml and url encoding more information can be found at : http://en.wikipedia.org/wiki/Base64

Base7, Base10, Base16, Base52, Base62

The name of the library is called Base64Encoder but it also provides other base converters. All converters inherit from a base class BaseCalculater which can convert any byte array to/from a specific base encoding character set. I needed a Base52 encoder so that is the reason that I refactored the code to support this and I added Base7, Base10 and Base16 just for demo purpose. The Base62 is included because it is pretty common as it solves the web incompatibilities of Base64 encoding.

Performance

So lets talk about performance! As why would you use it when you can use the version of the .net framework?

FromBase64

Base64 encoding is about twice as fast compared to Convert.ToBase64String. I did not expect that it is much faster that the framework itself! This is probably because the current implementation does not do any validation on the incoming Base64 string.

ToBase64

Base64 decoding performance is almost equal to Convert.FromBase64String. Sometimes its faster but usually performance can be assumed equal.

Knows issues

• The string.ToCharArray seems to cause a performance problem but because the code is currently as fast as Convert (for ToBase64) or significantly faster (FromBase64, two times faster) so it currently does not have my priority.
• The FromBase64 method does not do any validation! So if you need to convert external encoded Base64 strings then make sure you have validated the Base64 string! The readonly field Base64Encoder.CharacterSet can help validate your Base64 input.

Future

• I probably going to extend it to allow passing Stream as input just to make it more complete.