From: "Marin David Condic, 561.796.8997, M/S 731-96" <condicma@PWFL.COM>
Subject: Re: Resonable to assume format Stream_IO = Direct_IO?
Date: 1997/10/03
Date: 1997-10-03T00:00:00+00:00 [thread overview]
Message-ID: <97100309420454@psavax.pwfl.com> (raw)
Dale Stanbrough <dale@GOANNA.CS.RMIT.EDU.AU> writes:
>
>I know that Dec's Ada83 compiler put all sorts of extra things into
>a direct_io file; is this implementation freedom still taken advantage
>of by Ada95 vendors?
>
My experience with VMS files is that they store all sorts of stuff
in files (and their headers) besides the data. VMS imposed
structure on a file beyond just a file name and a bag of bytes.
This is true even for text files. This is why it is very difficult
to duplicate the "COPY" DCL command since there's so much hidden
information that's carried along with the file. So VMS would be a
bad example. (More an OS issue than a compiler implementation
issue.)
Unix tends to treat all files as a simple stream of bytes, so I'd
expect the stream_io stuff might work in most cases as you'd
expect. But so much of this seems like it will depend on if the OS
provides some sort of specialized file structure. I could imagine,
for example, that if an OS provided some kind of ISAM file,
direct_io might map on top of that rather easily, but stream_io
wouldn't be able to look at it without getting lots of garbage
data.
Is the platform you're looking at a Unix environment?
MDC
next reply other threads:[~1997-10-03 0:00 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-10-03 0:00 Marin David Condic, 561.796.8997, M/S 731-96 [this message]
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1997-09-30 0:00 Resonable to assume format Stream_IO = Direct_IO? Dale Stanbrough
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