Re: Cannot get pipes to work with glibmm

[Bastien Dalla Piazza <bastien dallapiazza gmail com>]

Hi again, I partially solved my problem:

One needs to call Glib::IOChannel::flush() after writing on outgoing
pipe for the message to be passed.
For the ingoing pipe, it is necessary to add a watch function using for
instance

Glib::io_signal().connect(sigc::mem_fun(&object,Object::callback),ingoing_fd, 
                          Glib::IO_IN);

I'm running into an other problem: Using the abow call, the function

bool Object::callback(Glib::IOCondition cond)

will be called each time the Glib::IO_IN condition is set on the ingoing
pipe, that is when there is something to read.

But trying to read in the above callback function using

Glib::IOChannel::read_to_end

results in an infinite loop (at least it looks like it).
The Glib::IOChannel::read_line still works so I tried the following
workaround:

Glib::ustring store,buf;
while(ingoing->get_condition() & Glib::IO_IN){
    ingoing->readline(buf);
    store.append(buf);
}

The while loop seems to finish, but then my callback function keeps
being called over and over again by the main loop (Gtk::Main::run()), as
if the Glib::IO_IN condition was never unset although the above while
loop did finish.

Am I doing things in an unexpected way, or is it possible there is a bug
in Glib::IOChannel ?

Thanks!

Le samedi 17 octobre 2009 Ã 17:37 +0200, Bastien Dalla Piazza a Ãcrit :
> Hi,
>
> I don't know if this is the correct mailing list so redirect me if not.
>
> In a Gtkmm project, I'm using Glib::spawn_async_with_pipes to execute
> and control a child process (gnugo in the example). But I cannot get it
> to work!
> For example:
> In the following code, I just redirect the gnugo stdin and stdout to my
> program:
>
> #include <glibmm.h>
> #include <vector>
> #include <string>
> #include <iostream>
>
> int main(int argc, char** argv)
> {
>     Glib::init();
>
>     int fd_stdin, fd_stdout; //file descriptors
>     Glib::Pid pid;
>     Glib::RefPtr<Glib::IOChannel> ch_stdin, ch_stdout;
>
>     std::vector<std::string> arguments;
>     arguments.push_back("gnugo");
>     arguments.push_back("--mode");
>     arguments.push_back("gtp");
>
>     /spawn gnugo
>     Glib::spawn_async_with_pipes(Glib::get_current_dir(),
>                              arguments,Glib::SPAWN_SEARCH_PATH,
>                              sigc::slot<void>(),
>                              &pid,&fd_stdin,&fd_stdout);
>
>     //create the IOChannel from the file descriptors
>     ch_stdin=Glib::IOChannel::create_from_fd(fd_stdin);
>     ch_stdout=Glib::IOChannel::create_from_fd(fd_stdout);
>
>     Glib::ustring input,output;
>
>     //a stupid loop to test whether the pipes work
>     while(true){
>         std::cin>>input;
>         ch_stdin->write(input.append("\n"));
>         ch_stdout->read_to_end(output);
>         std::cout<<output<<std::endl;
>     }
> }
>
> Any idea what I am doing wrong?
>
> Thanks!