Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!intercon!news
From: amanda@mermaid.intercon.com (Amanda Walker)
Newsgroups: comp.sys.mac.programmer
Subject: Re: FSWrite moving memory? (was Re: Think C 4.0 questions)
Message-ID: <1990Feb13.173605.7633@intercon.com>
Date: 13 Feb 90 17:36:05 GMT
References: <10193@hoptoad.uucp> <2032@cbnewsk.ATT.COM>
Sender: @intercon.com
Reply-To: amanda@mermaid.intercon.com (Amanda Walker)
Organization: InterCon Systems Corporation, Sterling, VA
Lines: 22

In article <2032@cbnewsk.ATT.COM>, ech@cbnewsk.ATT.COM (ned.horvath) writes:
> To digress a moment, PBOpen also has an "asynchronous" option, which
> would seem to contradict Tim Maroney's conjecture that async implies
> "does not move memory."

I think we still have a small confusion here.  When you make a file system
call asynchronously, all it does is insert the request into the file system
queue.  *That* operation does not move memory, which is why you can do it
at interrupt time (along with the fact that Enqueue & Dequeue handle
interlocking on the queue).  The actual file operations themselves may
(although I don't know, offhand, never having dug into the file system
code myself), but they are not done at interrupt time.

The file system doesn't do "real" :-) asynchronous I/O, but it does let you
queue up operations asynchronously.

--
Amanda Walker
InterCon Systems Corporation

"Many of the truths we cling to depend greatly upon our own point of view."
	--Obi-Wan Kenobi in "Return of the Jedi"