Re: [PATCH/RFC 07/11] run-command: support input-fd

[Erik Faye-Lund <kusmabite@googlemail.com>]

On Fri, Nov 27, 2009 at 9:14 PM, Johannes Sixt <j6t@kdbg.org> wrote:
> On Freitag, 27. November 2009, Erik Faye-Lund wrote:
>> What do you find confusing about it? The idea is to use a provided
>> bi-directional fd instead of a pipe if async->out is non-zero. The
>> currently defined rules for async is that async->out must be zero
>> (since the structure should be zero-initialized).
>
> It is just the code structure that is confusing. It should be
>
>        if (async->out) {
>                /* fd was provided */
>                do all that is needed in this case
>        } else {
>                /* fd was requested */
>                do all for this other case
>        }
>        /* nothing to do anymore here */
>
> (Of course, this should only replace the part that is cited above, not the
> whole function.)
>

OK. I've reimplemented the change for the next round, taking this into account.

>> Indeed it does. Do we want to extend it to support a set of
>> unidirectional channels instead?
>
> Yes, I think so. We could pass a regular int fd[2] array around with the clear
> definition that both can be closed independently, i.e. one must be a dup() of
> the other. struct async would also have such an array.
>

OK. This has been included for the next round. Instead of an array,
I've tried to be consistent with start_command, and used two
variables, "in" and "out".

> Speaking of dup(): The underlying function is DuplicateHandle(), and its
> documentation says:
>
> "You should not use DuplicateHandle to duplicate handles to the following
> objects: ... o Sockets. ... use WSADuplicateSocket."
>
> But then the docs of WSADuplicateSocket() talk only about duplicating a socket
> to a separate process. Perhaps DuplicateHandle() of a socket within the same
> process Just Works?
>

It seems the rest of the Windows-world depends on DuplicateHandle()
working for sockets, so I'm not too worried. I can't find anything
documentation(1) for _dup, and I don't think we have our own
dup()-implementation.

(1) http://msdn.microsoft.com/en-us/library/8syseb29(VS.71).aspx

-- 
Erik "kusma" Faye-Lund