🚀 go-pugleaf

In article <4gg5nk$he1@salyko.cube.net>
           medardus@cube.net "Andreas Karnetzki" writes:

>sherlock@micronet.fr schrieb:
>> natewild@mbnet.mb.ca (Nathan T. Wild) wrote:
>
>> >In C, why would one use open and DOS int handles rather than fopen and
>> >stdio file handles?
>
>> >Is there some speed advantage or differnet functionality?
>
>
>> because files opened using open and DOS files handles can be read and
>> write at the same time, while stdio files can't.
>
>That's not correct, I think. You can open files for read/write with the
>the stdio routines, too. Just use the "w+", "r+" or "a+" open modes with
>fopen().
>
>        fopen( "New.dat", "w+" );
>
>opens a file starting with 0 bytes for writing but with the possibility 
>to switch to read mode without the need of closing it.
>
>        fopen( "Old.dat", "r+" );
>
>opens an (existing) file starting with reading with the possibility to
>switch to writing without closing.
>
>        fopen( "Any.dat", "a+" );
>
>opens for appending and maybe reading afterwards.
>
>The only thing to assure for read/write switches is to use an
>fseek() call between read and write operations:
>
>        fp = fopen( "My.dat", "r+" );
>        fwrite( "Hello", 1, 5, fp );
>        fseek( fp, 0L, SEEK_SET );

You could have fflush(), rewind() or fsetpos() instead here.

>        fread( Message, 1, 5, fp );
>        fseek( fp, 0L, SEEK_CUR );

You could have rewind() or fsetpos() instead here.

>        fwrite( " and Goodby.", 1, 12, fp );
>        fclose( fp );

>The main difference between stdio calls and the "low-level" routines
>(not only under DOS but for Unix too) is the absence of buffering in
>the low-level functions.

The 'low-level' functions typically have buffering in the OS. However
stdio typically implements an extra level of buffering local to the
particular program.

>if you use fwrite(), for example, you can not be sure that the number of 
>bytes you want to write are actually written to the output at that time.
>The "real" write operation will take place if the stdio buffer for that
>file is full.

A good implementation of fwrite could bypass the stdio buffering where the
block sizes were appropriate.

-- 
-----------------------------------------
Lawrence Kirby | fred@genesis.demon.co.uk
Wilts, England | 70734.126@compuserve.com
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