RAR decompression algorithm

I'm looking for the description of an algorithm that can be used to decompress RAR files. I don't need to create new archives, only decompress existing ones.

The Wotsit.org has the description of the RAR file format (version 2), but the description does not describe the decompression algorithm.

Also, does anyone know whether RAR version 3 introduced any significant changes to the file format itself?

From stackoverflow

• You can get the source for UnRAR at the WinRAR site.

  Vojislav Stojkovic : Okay, now I feel sheepish. I missed that completely. Is this question stupid enough to warrant deleting?

  Steven Robbins : No, because then I might lose my rep ;-)

  Adam Davis : Nope, leave it up. It will help others.

  Argalatyr : @Vojislav: half of the questions on SO are less useful than yours! Don't be silly.