Board:   [WWIVnet] WWIV Development
Subject: Re: wrangling packets... need to learn to wrangle Type-2 msg
From:    Rushfan #1 @513
To:      Xenos #1 @60
Date:    Tue Sep 10, 2024 22:58

X> i need a nudge in the right direction for grappling with reading/writing
X> type-2
X> messages... maybe sample code for a stand-alone util that just reads
X> from one
X> sub, or posts to a sub.
X>

I can't find anything I wrote up about it unfortunately, but the basics of the
gat stuff is the message text file (.dat) is a repeating series of:
  header (aka gat)
  text blocks

The text blocks are a linked list of the next block or -1 for the last block,
it's much like the FAT filesystem.

msg.stored_as is the way to find that first block.   You need to jump to the
section and then offset.  To find the section, it's basically

sectiuon = msg.stored_as / GAT_NUMBER_ELEMENTS (which is 2048)
offset = msg.stored_as % GAT_NUMBER_ELEMENTS

So you seek to the gat section + (512 /* block size */ * offset)
The start of the gat section is: section * GATSECLEN + GAT_SECTION_SIZE

(all of these constants are in https://github.com/wwivbbs/wwiv/blob/main/sdk/msg
api/type2_text.h).

Let me know if this high level info is helpful.
rushfan
.