In various places, a PKWare library is used (often called implode.dll) that implements an uncommon, proprietary compression algorithm.
This algorithm was reverse-engineered by Ben Rudiak-Gould back in 2001, and Mark Adler wrote a C implementation in 2003.
This project is a translation into C# of the PKWare compression algorithm implemented in C by Mark Adler.
This implementation varies from the C original (see below).
Notes on the Blast/implode format taken from the original code are collated in this repository. Code comments may also help understanding the format.
I found that the files compressed in the legacy system I came into contact with contained multiple, separate, compressed streams. Each stream is delineated by an end of stream marker. Where the base implementation stops at the end of stream, this implementation checks for further data on the stream and will start decompressing again if it finds any.
This is probably the least elegant way of implementing a decompressor. It would be much better to implement Stream, for example. However, it does what it says on the tin; it decompresses the stream. If this was being used for something that was important, you might go to the trouble of making it work better. For me, though, this works faster than shelling out to an executable as the previous system did.
new Blast.BlastDecoder(sourceStream, destinationStream).Decompress();