[Caml-list] nonblocking I/O - using channels or Unix.file_descr ?

[Caml-list] nonblocking I/O - using channels or Unix.file_descr ?

[Basile STARYNKEVITCH]

Dear All,

I want to code nonblocking IO on Linux (I am not concerned with
"portability" problems to non-unix system). Of course I will use
Unix.select to wait for availability of input and output.  (I do not
want to use multithreading here  because I might have several dozens of such
I/O "ports" thru Unix named FIFOs).

Can I use Pervasives channels and then

Unix.set_nonblock (Unix.descr_of_in_channel myinchan)
Unix.set_nonblock (Unix.descr_of_out_channel myoutchan)

and then read & write bytes with
  Pervasives.input myinchan buf pos len
  Pervasives.output myoutchan buf pos len

or should I do the buffering explicitly myself using only Unix.read
and Unix.write


Apparently, the code in ocaml/byterun/io.c (notably the do_read and
do_write internal functions there) seems to be able to deal with
nonblocking channels, but I am not fully sure of this.

Regards
-- 

N.B. Any opinions expressed here are only mine, and not of my organization.
N.B. Les opinions exprimees ici me sont personnelles et n engagent pas le CEA.

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Basile STARYNKEVITCH   ----  Commissariat à l Energie Atomique * France
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Re: [Caml-list] nonblocking I/O - using channels or Unix.file_descr ?

[Xavier Leroy]

> I want to code nonblocking IO on Linux (I am not concerned with
> "portability" problems to non-unix system). Of course I will use
> Unix.select to wait for availability of input and output.  (I do not
> want to use multithreading here  because I might have several dozens of such
> I/O "ports" thru Unix named FIFOs).
> 
> Can I use Pervasives channels and then
> 
> Unix.set_nonblock (Unix.descr_of_in_channel myinchan)
> Unix.set_nonblock (Unix.descr_of_out_channel myoutchan)
> 
> and then read & write bytes with
>   Pervasives.input myinchan buf pos len
>   Pervasives.output myoutchan buf pos len

Yes -- the bytecode thread library does just that.
Be prepared to handle the Sys_blocked_io exception that will be raised
by Pervasives I/O functions when they cannot complete without
blocking.

- Xavier Leroy
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