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From: Bruce.Hoult@bbs.actrix.gen.nz
Newsgroups: comp.arch
Subject: Re: Async system interface
Message-ID: <1991Feb7.020237.15802@actrix.gen.nz>
Date: 7 Feb 91 02:02:37 GMT
References: <3177@crdos1.crd.ge.COM> <13772@lanl.gov>
Sender: Bruce.Hoult@actrix.gen.nz (Bruce Hoult)
Organization: Actrix Information Exchange, Wellington, New Zealand
Lines: 23
Comment-To: jlg@lanl.gov

Jim Giles writes:
>You should never be forced to do a wait system
>call if what you want is synchronous I/O.  The I/O call (below, RW
>stands for _either_ the read or the write system call) should be
>something like the following:
> 
>RW(fd,nw,buf,da,aflag,handle)

[rest of description deleted]

Once again, that is almost *exactly* the way the Mac does it.  The main
difference is that the Mac splits out your "da" parameter into two
parameters: an offset (+ve, -ve or zero), and a positioning mode which can
be "from start of file", "from where the last transfer finished", or "from
end of file".  Also, your "aflag" parameter is split into two: an actual
anync flag, and a result code that acts in almost exactly the way you
indicate -- it is +ve during the i/o, zero on success, and has a -ve error
number on failure.
-- 
Bruce.Hoult@bbs.actrix.gen.nz   Twisted pair: +64 4 772 116
BIX: brucehoult                 Last Resort:  PO Box 4145 Wellington, NZ
"And they shall beat their swords into plowshares, for if you hit a man
with a plowshare, he's going to know he's been hit."