Re: Problem using g_io_add_watch

["Rosfran Borges" <rosfran gmail com>]

Hi,
I can see something wrong in your code: you do not have to check the
GIOCondition using the "==" operator, just because its content is a XORed
sequence of integers. If you do something like this: if ( ( condition &
G_IO_IN ) != 0 ), everything will gonna be alright. The condition variable
is a kind of "bit field", and G_IO_IN may be one of the checked bits, among
many others (G_IO_OUT, G_IO_PRI, G_IO_ERR).

Yet, I suggest you to do the following: add the G_IO_HUP to the command
g_io_add_watch, and return the function if this buffer condition had been
received. For example:

g_io_add_watch(log_channel, G_IO_IN | G_IO_HUP, on_buffer_in,
(gpointer)log_buffer);

And inside the iochannel callback, check for the G_IO_HUP and return if this
condition is checked...

[]'s
Rosfran Borges

On Wed, Jun 25, 2008 at 2:45 PM, sinsedrix <sinsedrix gmail com> wrote:

> Oups,
>
> I realised that my IO callback function was not well written, so I wrote a
> new one.
>
> PROBLEM : Now the problem is that this IO callback is called continuously
> in
> main loop even if nothing
> is written in the watched file.
>
> I noticed that if I return FALSE, the callback is called once but is no
> longer called on a
> write on the watched file.
>
> Should I do some SEEK operation on the file or on the GIOChannel ?
>
> Thanks
>
> Here is the new callback :
>
> ======================================================
> gboolean
> io_callback_end(GIOChannel *source, GIOCondition condition, gpointer data)
> {
>    gchar * str_return;
>    gsize length;
>     GtkTextIter end;
>    GError * error = NULL;
>    GtkTextBuffer * buffer = (GtkTextBuffer *)data;
>
>     if(condition == G_IO_IN) {
>        GIOStatus status = g_io_channel_read_to_end(source, &str_return,
> &length, &error);
>        gtk_text_buffer_get_end_iter (buffer, &end);
>        gtk_text_buffer_insert(buffer, &end, str_return, length);
>
>         switch(status) {
>        case G_IO_STATUS_ERROR:
>            g_debug("G_IO_STATUS_ERROR : on_buffer_in");
>            break;
>        case G_IO_STATUS_NORMAL:
>            g_debug("G_IO_STATUS_NORMAL : on_buffer_in %s", str_return);
>            break;
>        default:
>            g_debug("Should not be here : on_buffer_in");
>        }
>
>        g_free(str_return);
>    }
>    return TRUE;
> }
> ======================================================
>
>
> 2008/6/25 sinsedrix <sinsedrix gmail com>:
>
> > Hello,
> >
> > Problem: When I call g_io_add_watch my application is crashing with no
> > explanation.
> >
> > Here is the shorter file I could write to expose my probem using
> > g_io_add_watch :
> >
> > ==========================================================
> > #include <stdio.h>
> >
> > #include <gtk/gtk.h>
> >
> > static FILE * MyLogFile = NULL;
> >
> > void write_in_file(GtkButton * b, gpointer user_data) {
> >     static int i = 0;
> >     fprintf(MyLogFile, "Something written %d\n", i);
> >     i++;
> > }
> >
> > gboolean            on_buffer_in                        (GIOChannel
> > *source,
> >                                                          GIOCondition
> > condition,
> >                                                          gpointer data) {
> >     gchar ** str_return = NULL;
> >     gsize * length = NULL;
> >     GtkTextIter end;
> >     GError * error = NULL;
> >     GtkTextBuffer * buffer = (GtkTextBuffer *)data;
> >
> >     g_io_channel_read_to_end(source, str_return, length, &error);
> >     gtk_text_buffer_get_end_iter (buffer, &end);
> >     gtk_text_buffer_insert(buffer, &end, *str_return, *length);
> >
> >     return FALSE;
> > }
> >
> > void my_exit() {
> >     fclose(MyLogFile);
> >     gtk_exit(0);
> > }
> >
> > GtkWidget * create_window(void) {
> >     GtkWidget *window;
> >     GtkWidget *vbox_win;
> >     GtkWidget *button;
> >
> >     GtkWidget *log_view;
> >     GtkTextBuffer *log_buffer;
> >     GIOChannel * log_channel;
> >
> >     window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
> >     gtk_window_set_title (GTK_WINDOW (window), "TestGIO");
> >
> >     vbox_win = gtk_vbox_new (FALSE, 5);
> >     gtk_widget_show (vbox_win);
> >     gtk_container_add (GTK_CONTAINER (window), vbox_win);
> >
> >     log_buffer = gtk_text_buffer_new(NULL);
> >     log_view = gtk_text_view_new_with_buffer(log_buffer);
> >     gtk_widget_show(log_view);
> >     gtk_text_view_set_editable(GTK_TEXT_VIEW(log_view), FALSE);
> >     gtk_box_pack_start (GTK_BOX (vbox_win), log_view, TRUE, TRUE, 0);
> >
> > #ifdef MSDOS
> >     log_channel = g_io_channel_win32_new_fd(fileno(MyLogFile));
> >     g_debug("Windows Log file %d %p", fileno(MyLogFile), log_channel);
> > #else
> >     log_channel = g_io_channel_unix_new (fileno(MyLogFile));
> >     g_debug("Unix Log file %d %p", fileno(MyLogFile), log_channel);
> > #endif
> >
> >     // The line that crashes :
> >     g_io_add_watch(log_channel, G_IO_IN, on_buffer_in, (gpointer)
> > log_buffer);
> >
> >     button = gtk_button_new_with_label("Write something");
> >     gtk_widget_show(button);
> >     gtk_box_pack_start (GTK_BOX (vbox_win), button, FALSE, FALSE, 0);
> >
> >     g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK
> > (write_in_file), NULL);
> >
> >     return window;
> > }
> >
> > int
> > main (int argc, char *argv[])
> > {
> >   GtkWidget *window;
> >
> >   gtk_set_locale ();
> >   gtk_init (&argc, &argv);
> >
> >   MyLogFile = fopen("./MyLogFile.txt", "w+");
> >   g_debug("Log file number : %d", fileno(MyLogFile));
> >
> >   window = create_window ();
> >   g_signal_connect(G_OBJECT(window), "destroy", G_CALLBACK (my_exit),
> > NULL);
> >   gtk_widget_show (window);
> >
> >   gtk_main ();
> >   return 0;
> > }
> > ========================================================
> >
> > 2008/6/19 Tor Lillqvist <tml iki fi>:
> >
> > > Problem: When I call g_io_add_watch my application is crashing with no
> > > explanation.
> > >
> > > Can you provide a *minimal* but *complete* sample program (just one
> > > source file) that crashes in the same way?
> > >
> > > > PS: I had a problem with GIOChannel before because I was using Cygwin
> > > gcc to
> > > > compile (linking with kernel32 and user32) and I read somewhere that I
> > > > should use MinGW gcc
> > >
> > > If you use the Windows GLib packages from ftp.gnome.org, then yes,
> > > they are not for use by Cygwin programs, so you should use mingw to
> > > compile code that uses them.
> > >
> > > >  (linking with wsock32) instead, is it right ?
> > >
> > > wsock32 in particular has little to do with it. Cygwin is just a
> > > completely different operating system (even if it happens to run on
> > > top of Windows), so you should not use non-Cygwin libraries in Cygwin
> > > programs. (Unless in very special cases when you know exactly what you
> > > are doing. GLib is not such a case.)
> > >
> > > --tml
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