RFC: AnyEvent::Handle with two non-duplex filehandles

[Mark Lawrence]

On Mon Apr 22, 2013 at 11:10:27AM +0200, Marc Lehmann wrote:
> 
> create a socketpair, fork, dup it over stdin and stdout, exec ssh and
> you are done. no need for fancy modules either.

Ok, until now all I had considered was pipe-based communication. Thanks
for the tip.

> I didn't know open returned or required two handles, how do you do
> that?

I didn't quite mean it that way. What I meant was it either allows for
reading, or writing, but not both together.

> > IPC::* etc) all seem to return or require separate in/out
> 
> Are you sure they require separate handles? That happens when you
> pass in the same handle for stdin and stdout?

Given that they are mostly pipe based (one-directional at least on
Linux) I would expect this to fail, but I haven't confirmed this.

> >     $state = calculate_state(); $whl->push_write(...);
> > 
> >     $rdl->push_read(line => sub { $state = calculate_state_again();
> > 
> >         # handle the read, and then push another write...
> >         $whl->push_write(...); $rdl->push_read(...); });
> 
> <....>
> 
> The easy solution that should alwas work is have a wrapper object
> that only points to the real object(s) - since nothing inside keeps a
> reference to the wrapper, it's DESTROY can unravel the object
> hierarchy. XML::Parser uses this for example.

Do you mean something like this?:

    my $wrapper;
    $wrapper = bless {
        handle => AnyEvent::Handle->new(
            on_read => sub {
                my $hdl = shift;
                # access other things with $wrapper->{other}
            },
        ),
        other => $thing,
      },
      'MyWrapper';

However as I see it, I have still created a ref-count issue of some
kind here: $wrapper contains a reference to itself inside the subref,
no?

Ideally perhaps I would make an AnyEvent::Handle object the wrapper,
and add other things to _it_? Then there is no need for variables to be
scoped inside anonymous subrefs:

    my $handle => AnyEvent::Handle->new(
        other   => $thing,
        on_read => sub {
            my $hdl = shift;

            # access other things with $hdl->{other}
        },
    );

-- 
Mark Lawrence