Path: utzoo!mnetor!uunet!cbmvax!steveb
From: steveb@cbmvax.UUCP (Steve Beats)
Newsgroups: comp.sys.amiga
Subject: Re: UnDelete & DiskSalv Question
Message-ID: <3325@cbmvax.UUCP>
Date: 16 Feb 88 15:47:43 GMT
References: <18956@aspvax.UUCP> <41962@sun.uucp>
Reply-To: steveb@cbmvax.UUCP (Steve Beats)
Organization: Commodore Technology, West Chester, PA
Lines: 27

In article <41962@sun.uucp> cmcmanis@sun.UUCP (Chuck McManis) writes:
>
>Well, I don't know this for sure, but when you "Delete" something I 
>believe that AmigaDOS scribbles on the FileHeader block. When you "Lose"
>something because the directory got blown away, you can recover it. 
>The only other way is an extremely crufty walk through the old file
>system collecting blocks that all point back to the same block. Not
>fun.
>
When AmigaDOS deletes a file it does not scribble over the deleted header.
In the current file system, the header in question has it's type or'ed with
t.deleted and MAY be written to disk in this state (I'm not sure without
trying it out).  The only headers that have any important info changed are
the owning directory and/or the previous header in the hash chain.  In FFS
the t.deleted thingy has been removed, now only the previous header gets
changed and written to disk.  The file that was deleted will remain intact
exactly where it was before the delete.  Oh yes!  In the old FS, bitmap
pages can be de-allocated and re-allocated when they are written out.  If
the file that was deleted was closer to the root than the current bitmap
then the chances are it will be zonked (though this will probably only
affect the data and not the header due to allocation directions).

>--Chuck McManis
>uucp: {anywhere}!sun!cmcmanis   BIX: cmcmanis  ARPAnet: cmcmanis@sun.com
>These opinions are my own and no one elses, but you knew that didn't you.

Steve Beats