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From: ohk@edeber.tfdt-o.nta.no (Ole-Hjalmar Kristensen FOU.TD/DELAB)
Subject: Re: CRC in Ada?
Date: 1997/03/10
Message-ID: <OHK.97Mar10135200@edeber.tfdt-o.nta.no>#1/1
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References: <1997Mar2.220652@nova.wright.edu> <oslo83b70l.fsf@ted.vigra.com>
Organization: Telenor Online Public Access
Newsgroups: comp.lang.ada
Date: 1997-03-10T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <dewar.857911919@merv> dewar@merv.cs.nyu.edu (Robert Dewar) writes:

   OUe-Hjalmar says

   > I think you are missing something here. Altough in Unix it IS possible
   > to do reads of arbitrary length, the standard IO library of C
   > definitely does IO in blocks. The getc/putc functions are
   > usually implemented as macros, which just manipulate the buffer. Of


   You cannot make such statements (the standard IO lbrary of C definitely
   does IO in blocks). The standard speaks only of interfaces, not of
   implementation, there is nothing in the standardized interface that requires
   IO to be done in blocks. This may be an implementation characterstic of some
   or even most or even all current implementations, but it is NOT a fundamental
   property of the standard IO library.

Yes, of course you are right. I plead guilty of using imprecise language.

But I still would say that this is the only reasonable implementation,
especially as functions to explicitly control the buffering and flush
the buffer is part of the specification.  You could just as well argue
that if you use the write system call, you have no guarantee that the
OS does not actually write a single byte at a time to the disk...
Maybe the standards should say something about the precise semantics
at this level as well.

Anyway, you seem to have missed my point, which is that as all the
Unix standard IO libraries I am aware og does block IO anyway, it
would not be any harder to implement such a library on any other OS
which have block IO but not single char IO as part of the system
calls.
The flexibility of the Unix read and write calls is not needed by the
usual implementations of the C standard IO library.

Ole-Hj. Kristensen