OpenEuphoria

Re: Bug with where()?

• Posted by Juergen Luethje <jluethje at gmx.de> Jul 27, 2002
• 389 views

Rob <rds at RapidEuphoria.com> wrote:

> Juergen writes:

>> After activating the command flush(f), the program works as expected,
>> but I think it also should work correctly without flush(f).

> Thanks for your example.
> I duplicated your results.
> I think this is an example of what I say in the docs
> for seek():

> "After seeking and reading (writing) a series of bytes,
> you may need to call seek() explicitly before you switch
> to writing (reading) bytes, even though the file position
> should already be what you want."

Before writing the program, I read your documentation for seek(), but
now it seems to me, that I didn't understand it 100%. In my program, I
used seek() immediately before puts(), but nowhere else. This lead to
the known problems.
Now, having read your hints, I inserted another seek() statement
immediately before gets(), and now the program works correctly without
flushing.
Thanks! Obviously, it was not so easy for me to understand.  

> Explicit seeking, or flushing corrects these problems.

Do these problems only occur when where() is used?

> Your example ran the same (undesired) way with the DJGPP-built
> interpreter as well. This seems to be a basic problem with C I/O.
> It's not really under my control, except that I could do a forced,
> hidden flush(), in some cases, causing a possibly severe loss of
> performance.

I see.

> One minor thing. I recommend that you use "ub", rather than "u",
> although it doesn't seem to matter in your example...

> "This function [seek()] is normally used with files opened in
> binary mode. In text mode, DOS [and Windows]
> converts CR LF to LF on input, and LF to CR LF on output,
> which can cause great confusion when you are trying to count bytes."

I wanted to use gets(), because it's much easier for me, to think of a
file as a "list of lines", rather than a stream of bytes. And I
erroneously assumed, that gets() couldn't be used for files that are
opened in binary mode.

> Regards,
>    Rob Craig
>    Rapid Deployment Software
>    http://www.RapidEuphoria.com

Thanks for your advice!

Regards,
   Juergen