The LZW functions simply compress and decompress data in memory buffers.

dword lzw_compress(dest,src,size) is used to compress src and placing into
  dest for size bytes.
  It returns the size of the outputed data.

void lzw_decompress(dest,src) is used to decompress src and places the data
  into dest.  Returns only a error code if error occurs.

That's it, plan and simple.