Re: sigx synchronous requests?

[klaus triendl <klaus triendl eu>]

Milosz Derezynski schrieb:
> Hey everyone, and especially Klaus,
>
> I was wondering if there is a way to have synchronous (that is, achieved 
> by proper internal locking) requests on sigx threadables?
>
> I have the problem that currently I have a threadable class but I need 
> one specific synchronous call that immediately returns and passes a direct
> return value.
>
> I can achieve this probably by doing some manual locking and so on, but 
> I would prefer to do it with sigx directly if possible.

There is a way for synchronous requests: open_sync_tunnel() and 
open_sync_tunnel_with().

Since there's no direct way to express synchronous requests like 
sigx::request_f<> offers for async ones you have to write your own 
request wrapper function like so:

<code>
class mythread: public sigx::threadable
{
protected:
  // request handler
  int on_calc() { return 0; }

public:
  // request api
  int sync_calc();
};

int mythread::sync_calc()
{
  // sync request
  return sigx::open_sync_tunnel(
    sigc::mem_fun(this, &mythread::on_calc)
  );
}
</code>

I don't know exactly anymore why I didn't provide a sync_request_f<> 
wrapper, I guess the design rational was that it's not needed very often 
and that it's anyway better to use async requests.

Regards,
Klaus