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From: mneerach@iiic.ethz.ch (Matthias Ulrich Neeracher)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Is AppFile.vRefNum always WDRefNum???
Message-ID: <24152@neptune.inf.ethz.ch>
Date: 7 Feb 91 10:46:11 GMT
References: <1991Feb4.190115.1@gsbacd.uchicago.edu>
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In article <1991Feb4.190115.1@gsbacd.uchicago.edu>, gft_robert@gsbacd.uchicago.edu (opcode ranger) writes:
|> I have a question regarding the vRefNum field in the AppFile data type: under
|> HFS is this actually a WDRefNum?  Is it guaranteed to be a WDRefNum?

No. It is certainly not a WDRefNum for a file residing on a MFS volume, and
I believe also that it's no WDRefNum for files on the 'root' level of a HFS
volume.

|> My problem is this: I need to get the dirID (parent dir id) for each file I get
|> AppFile information for (i.e. for each file which is opened from the Finder
|> with the application).  If I know this field is a WDRefNum I can call
|> PBGetWDInfo() on it and find the dirID.  If it's not always a WDRefNum I'm not
|> sure if this call will work.

There is a Technote which describes a technique to determine whether a vRefNum
is a WDRefNum: WDRefNums are given numbers -32768, -32767, -32766 or, if you
prefer hex, $8000, $8001, $8002. Normal vRefNums have numbers 'close to zero'.

Matthias

-- 
Matthias Neeracher                                   mneerach@iiic.ethz.ch
   "These days, though, you have to be pretty technical before you can 
    even aspire to crudeness." -- William Gibson, _Johnny Mnemonic_