Subj : Tear lines
To   : AKAcastor
From : Digital Man
Date : Fri Apr 26 2024 11:07 am

  Re: Tear lines
  By: AKAcastor to Shurato on Thu Apr 25 2024 01:29 pm

 >  S> ---  shsbbs.net
 >  S> Shurato, Sysop Shurato's Heavenly Sphere (ssh, telnet, pop3, ftp,nntp,
 >  S> ,wss) (Ports 22,23,110,21,119,8080) (ssh login 'bbs' pass 'shsbbs').
 >
 >  S> *** THE READER V4.50 [freeware]
 >  S> ---
 >  S>  * Origin: Shurato's Heavenly Sphere telnet://shsbbs.net (21:2/148)
 >
 > I have a question about 'tear lines' on messages.  If Digital Man is reading
 > this maybe he'll have some insight as a long term developer of
 > FTN-compatible systems.  Or anyone else of course please jump in.
 >
 > I have a vague recollection of there being issues around "multiple tear
 > lines" in messages - IIRC it's a topic I saw discussed in the 90s.  In a
 > very brief search I didn't find anything specifying that there can be only
 > one tearline, so I could be chasing a false memory here. :)
 >
 > I'm not aware of any actual issues around multiple lines looking like a tear
 > line (at least on my system running Squish and Maximus it seems fine), so
 > I'm not reporting a problem or anything - just curious if there are
 > technical edge-cases around tear lines in messages as I seem to remember in
 > the past some people being picky about it.
 >
 > (I would expect software that cares about a tearline to search for the line
 > starting with "---" from the end of the message anyway, eliminating any
 > potential issue.)

I can only really speak about how Synchronet/SBBSecho handles (multiple) tear-lines:

1. Tear-line are forward-parsed from the message text (the first tear line found is consider *the* tear line for the message). Though the backward-parse theory seems to make sense, in the case there *are* multiple tear lines in a message, there might be some ambiguity about which is the correct one (the first or the last) - so perhaps no decision (forward vs. backward) will be always correct for all cases.

2. The reason tear-lines matter (for Synchronet): the message "body" is stored separate from the "tail" of a message (which includes tear, origin, tag lines) and the tear line is what indicates the beginning of the message "tail". This allows message text searches and duplicate-message detectors to easily exclude the "tail text", as is usually desirable. There may be other advantages (e.g. easily inserting additional tear/tags upon export), but those are the main reasons for this design.

3. So when Synchronet is going to add a tear line to a message (e.g. when exporting to an FTN or QWKnet), it first converts any existing tear lines in the message text to something else (e.g. "---\n" becomes "===\n") to avoid the "multiple tear line" ambiguity.
-- 
                                            digital man (rob)

Synchronet/BBS Terminology Definition #44:
IMAP = Internet Message Access Protocol
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