Line buffering

Line buffering

[Richard Jones]

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Is there a way to set line buffering, particularly of stdout?

Rich.

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Re: [Caml-list] Line buffering

[Bruno.Verlyck]

   Date: Tue, 7 Dec 2004 13:57:45 +0000
   From: Richard Jones <rich@annexia.org>

   Is there a way to set line buffering, particularly of stdout?
Short answer: no.

The OCaml I/O system doesn't use C's FILE *.  It's (much) simpler,
efficient, and just not done with line buffering as a goal.  I looked
at it (io.c) while implementing Cash (line buffering is in the
original specification), and adding this would have made a too big
patch.  I gave up.

Bruno.

Re: [Caml-list] Line buffering

[Richard Jones]

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On Tue, Dec 07, 2004 at 07:10:00PM +0100, Bruno.Verlyck@inria.fr wrote:
>    Date: Tue, 7 Dec 2004 13:57:45 +0000
>    From: Richard Jones <rich@annexia.org>
> 
>    Is there a way to set line buffering, particularly of stdout?
> Short answer: no.
> 
> The OCaml I/O system doesn't use C's FILE *.  It's (much) simpler,
> efficient, and just not done with line buffering as a goal.  I looked
> at it (io.c) while implementing Cash (line buffering is in the
> original specification), and adding this would have made a too big
> patch.  I gave up.

I noticed before that OCaml seems to implement its own I/O buffering
system, instead of using FILE* (or sfio, I guess).  Is there a reason
for that?

Thanks for the info anyway.  It's somewhat annoying that stdout can't
be line buffered.

Rich.

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Re: [Caml-list] Line buffering

[Nicolas Cannasse]

> Thanks for the info anyway.  It's somewhat annoying that stdout
> can't be line buffered.

If you wrap the stdout with an ExtLib IO filter, you can buffer it how you
like.
But it will require changing your calls to printf by IO.printf for example.

Nicolas

Re: [Caml-list] Line buffering

[Xavier Leroy]

> I noticed before that OCaml seems to implement its own I/O buffering
> system, instead of using FILE* (or sfio, I guess).  Is there a reason
> for that?

Largely historical.  Early versions of Caml Light, circa 1990, had a
GC which did not play nice with "malloc", hence many standard C
library functions such as fopen() could not be used.  The buffering
code that I wrote at that time managed to survive until now.  

Also, bytecode-level threads (vmthreads) need to do non-blocking I/O
on I/O channels, and I don't think this could be done reliably with FILE*.
This said, one could also argue that bytecode-level threads are
another survivance of the past.

- Xavier Leroy