[boost] Re: Re: Asynchronous I/O

From: Robert Ramey (ramey_at_[hidden])
Date: 2005-03-29 10:53:02

Well put !!!

I have in fact implemented the aio interface in terms of windows API calls.
Aside from the fact that the windows API in this area is a little
"inelegant" it actually mapped quite well to the aio interface.

When I was faced with the problem of adding async i/o to my application, and
not wanting to make my application windows specific, I came upon aio.h.  I
implemented it in terms of windows API calls and got things working to my
satisfaction.  Afterwards, I believe I built and tested my app on a *nix
system with aio.  If I recall correctly, it worked as I hoped it would.

To this day I  have no idea how aio was implemented on a freeBSD machine.  I
doubt it added threads to my ap - though I can't say for sure.  It might
have relied on some lower level os API or it might have had native support
at the OS level.

So - it seems that if wants to use aio.h - its already there for atleast
some *nix systems.  If one want's to make it universal it can be implemented
for Win32 systems.  For other *nix systems it could be implemented in terms
of threads.

Robert Ramey

Jonathan Wakely wrote:
> On Tue, Mar 29, 2005 at 04:36:42PM +0300, Boris wrote:
>
>> Robert Ramey wrote:
>>> Windows has the concept of "Overlapped I/O" which permits dispatch
>>> of an i/o request that invokes a call back when done.
>>>
>>> Posix has aio which functions (I believe) in a similar way.
>>>
>>> So one has the concept of asyncronous i/o without any explicit
>>> reference to threads at least at the application level.
>>
>> I am not sure if I understand correctly. Just as Don I think we
>> can't get around threads when we have callbacks. I don't know about
>> Windows but the callback in aio (Posix) is done by creating a new
>> thread.
>
> How the kernel chooses to implement the aio system calls is an
> implementation detail - it certainly doesn't require use of
> Boost.Thread types!  I think what Robert was saying is that an
> application can use
> POSIX aio without ever having to use or know about POSIX threads.
>
> You and Don seem to be requiring that the application explicitly
> create
> and manage threads.  Several people have suggested they'd like to use
> some form of AIO without having to use threads.
>
> jon
>
> _______________________________________________
> Unsubscribe & other changes:
> http://lists.boost.org/mailman/listinfo.cgi/boost