Path: utzoo!utgpu!attcan!uunet!husc6!bloom-beacon!apple!blob
From: blob@Apple.COM (Brian Bechtel)
Newsgroups: comp.sys.mac.hypercard
Subject: Re: Getting information from the desktop
Message-ID: <20350@apple.Apple.COM>
Date: 10 Nov 88 15:32:17 GMT
References: <59820SAS102@PSUVM> <30733@think.UUCP>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 50

In article <30733@think.UUCP> ephraim@vidar.think.com.UUCP (Ephraim Vishniac) writes:
>In article <59820SAS102@PSUVM> SAS102@PSUVM.BITNET (Steven A. Schrader) writes:
>
>>Does anyone out there know how to get information such as what disk
>>is in which drive, etc.
>
>This information (and lots of other good stuff) is recorded in the
>Volume Control Block (VCB).  See the volume information calls among
>the file manager routines in IM II (old versions) or IM IV (HFS
>versions).  If you're writing in assembly language, you may find it
>easier just to walk the VCB list directly.  Apple will frown at you,
>of course, since looking directly at low-memory stuff is discouraged.

Okay, I'll bite.  Yes, Apple discourages you from walking the VCB queue
directly.  Use the method explained on page IV-129 and IV-130: pass in a
paramblock with a positive ioVolIndex.  This works, and doesn't break
the next time we modify the file system.  

Sample code follows:

. . . (You'll need Files.h at least)...

	short	i;
	OSErr	result;
	Boolean	foundIt;
	HVolumeParam	hParamBlock;
	
	result = noErr;
	foundIt = false;
	
/* loop until we find the volume we're looking for or get the
** "no such volume" error for this particular index
*/
	for (i = 1; result != nsvErr && foundIt == false; i++)
	{
		hParamBlock.ioCompletion = 0;
		hParamBlock.ioNamePtr = nil;
		hParamBlock.ioVRefNum = 0;
		hParamBlock.ioVolIndex = i;
		result = PBHGetVInfo(&hParamBlock,false);
		if ()	/* <== fill in your terminating condition */
			foundIt = true;
	}
	if (result == noErr)
		/* grab whatever information you were trying to get
		** about a specific volume.
		*/
. . .etc.

--Brian Bechtel		blob@apple.com		"My opinions, not Apple's"