Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!swrinde!ucsd!ucbvax!THUMPER.BELLCORE.COM!nsb
From: nsb@THUMPER.BELLCORE.COM (Nathaniel Borenstein)
Newsgroups: comp.soft-sys.andrew
Subject: Re: .MS_MsgDir
Message-ID: <cZQdiq20M2Yt4sTI5N@thumper.bellcore.com>
Date: 28 Nov 89 14:52:38 GMT
References: <19996@pasteur.Berkeley.EDU>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 23

First of all, the date field:  This is a UNIX-style date (seconds
since January 1, 1970, or something like that) converted from a long
into a base 64 string of six bytes.  The AMS libraries contain functions
for going into and out of base64, but of course that won't help you if
you're not using C; the code for them is in overhead/mail/lib/genid.c,
and should be easily converted to some other language.  (The rationale
for the base 64 stuff is lost in ancient history, but had to do with wanting
to put the dates in ASCII-readable form for things like file names, etc.
In retrospect, I don't care to defend it.)

The header part of the .MS_MsgDir file is basically a magic signature and
some directory-wide information.  Included in it are a major and minor version
number for the format of the .MS_MsgDir file itself.  That format hasn't
changed for years, and probably won't change any time soon, but checking it
is a good idea in case it changes some time in the future.  The actual format
of the header is fairly idiosyncratic, but easily understood if you know 
where to look.  The place to look, it turns out, is in ams/libs/ms/rawdb.c,
in a routine called DestructivelyWriteDirectoryHead.  That routine is what
normally writes out the directory headers, and it should be pretty easy
to tell, from that, what the format is.  (No, there is no formal spec
anywhere for the format.)

I hope that helps; if you need further help, don't hesitate to ask.