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From: stevec@Apple.COM (Steve Christensen)
Newsgroups: comp.sys.mac.programmer
Subject: Re: driver access
Keywords: device manager, disk manager lowlevel disk reading
Message-ID: <9473@goofy.Apple.COM>
Date: 28 Jul 90 01:32:50 GMT
References: <640@beguine.UUCP>
Organization: Apple Computer Inc., Cupertino, CA
Lines: 44

In article <640@beguine.UUCP> Eliot.Henry@samba.acs.unc.edu writes:
>I am trying to find a way to access the disk drives at the lowest level.
>I need to read and write to them at the bit level. I have tried pbread but am
>having trouble getting it to work. I am assuming that the driver for disks
>is open (but i did try calling open driver ".Sony" this caused another error
>saying the .sony was not recognized!   Help anyone please!

If you just want to get the contents of the 512 byte blocks on floppies, you
just need to do a PBRead().  The driver is already open so you don't need to
open it again.  Try something like this Pascal snippet:

	VAR pb        : ParamBlockRec;
	    theBuffer : PACKED ARRAY[1..512] OF SignedByte;
	...
	BEGIN
	...
	pb.ioRefNum:=-5;		{-5 is .Sony driver's refNum}
	pb.ioVRefNum:=xxx;		{drive number for floppies are 1,2[,3]}
	pb.ioBuffer:=@theBuffer;	{where to put the data}
	pb.ioReqCount:=512;		{how much to read}
	pb.ioPosMode:=FSFromStart;	{position is relative to first block}
	pb.ioPosOffset:=xxx;		{byte offset from start of disk}
					{ = 512 * disk block number}
	IF PBRead(@pb, FALSE)=NoErr THEN BEGIN
	  {do whatever processing on the data}
	END;

To read more data at a time, just allocate a bigger buffer and increase the
value in the ioReqCount field.  Theses should be a multiple of 512 bytes.
If you need to get at the disks at a lower level than the device manager,
that's not recommended since you'll break on the IIfx if not on some future
hardware as well...

steve
-- 
____________________________________________________________________

  Steve Christensen             Internet:   stevec@goofy.apple.com
  Apple Computer, Inc.          AppleLink:  STEVEC
  20525 Mariani Ave, MS 81-CS   CompuServe: 76174,1712
  Cupertino, CA  95014

  "You just contradicted me."  "No I didn't."
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