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From: mlelstv@faui44.informatik.uni-erlangen.de (Michael van Elst )
Newsgroups: comp.sys.amiga.tech
Subject: Re: Finding DOS Handler Message Ports
Message-ID: <662@faui44.informatik.uni-erlangen.de>
Date: 10 Oct 88 11:38:13 GMT
References: <5459@netnews.upenn.edu>
Reply-To: mlelstv@faui44.UUCP (Michael van Elst (kdebugger))
Organization: CSD., University of Erlangen, W - Germany
Lines: 33

In article <5459@netnews.upenn.edu> ranjit@eniac.seas.upenn.edu.UUCP (Ranjit Bhatnagar) writes:
>Alright, suppose I were writing a DOS handler which would filter
>packets given to it and pass them on to other handlers.  How can I,
>given a filename, figure out the handler corresponding to it without
>actually making any attempt to access the file (or device) in question?
>

There is a functions called DeviceProc in the dos.library.
You pass a filename to the function and it returns a pointer to
the corresponding handlers messageport. There you can send
DosPackets like ACTION_INHIBIT to stop the file system or
ACTION_FIND_INPUT to open a file for reading, etc.

The filename you pass to this functions doesn't need to refer
to an existing file.
You might stop dos from asking you to insert a disk if you want
to access a volume that is not mounted.
This is done by writing a -1 into your Process structure pr_WindowPtr
field. Don't forget to restore the original value.

You can find the handler that serves your current directory by
examining your Process structure pr_FileSys field.

The DeviceProc function cannot be used with CON: and RAW: handlers
because there might be more than one of each.
The Open call returns a BPTR to FileHandle. You can find the handler
port in the fh_Type field of this FileHandle structure.

Hope that helps.

				Michael van Elst

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