[nos-bbs] B2F (compression) success !!!

[Maiko Langelaar (ve4klm)]

Greetings all,

It turns out that B2F is essentially IDENTICAL to F6FBB compressed
forwarding. The ONLY difference in the compressed data stream is that
the B2F puts an extra 2 byte CRC in front of the regular F6FBB part.

In other words, it has nothing to do with the LZW compression, or
the number of bits. I was mistakenly reading the CRC as the actual
filesize (number of bytes that follow), when in fact the filesize
was the 2 bytes after the CRC. That explains the huge file sizes.

Minor code change solves that part. The only thing left to do now is
deal with the fact that with B2F all the message header information
is contained in the compressed data block, not in the proposal line
as happens in the FA style forwarding. Not a big deal (so far).

This is what a very simple B2F payload from an Airmail client looks
like after it's been Decoded (uncompressed) using JNOS lzw code that
has been modified to deal with the additional 2 byte CRC in front :

   MID: 1053_VE4PKT
   Date: 2008/03/23 19:57
   Type: Private
   From: VE4PKT
   To: ve4klm
   Subject: test
   Mbo: VE4PKT
   Body: 7

   testing

That's the latest for now.

Maiko