I've tried to write the new mbox code in a way that it could be moved into generic flat-file library with mbox-specific code being implemented on top of that.

The code would be useful for all formats that require modifying message headers to store the metadata. How many such are there?

I suppose all such formats could be implemented by separating mails into 3 logical parts:

• header ("From ...\n")
• mail data (headers and body)
• footer ("\n")

Except keeping a separate header and footer is kind of annoying, my current code uses:

• mail separator ("\nFrom ...\n")
• first message header's skip counter: how many characters to remove from mail separator for the first message (1, for \n before the "From ..")
• last message's footer

Somewhat uglier, but I think all needed formats could be implemented with it? It's also simper and more efficient to implement..

Besides mbox, I know at least two variations which are used:

AAAA-box:

• I remember seeing this somewhere years ago, but I'm not sure if it's still used or if it has a real name..
• separator is four ^A characters (ascii 1) and LF
• header skip counter is 5
• last message footer would be the same ^A^A^A^A\n

dotbox: prefixed with another '.'. the '.' prefixes will have to be removed for

• mails are stored in SMTP format, ie. lines beginning with '.' are

IMAP, so this isn't as simple as others to implement.

• separator is ".\n"
• header skip counter is 2
• last message footer is ".\n"

Any thoughts?