Tutorials/Using FSO glib for resource handling

To make live easy for C devolopers and have a contract between client and server, we are creating libfso-glib from the specs. This example shows how to list all available resource and request a resource including (some) error handling from C. Because we're using asynchronous DBus calls, it needs some callbacks and knowledge of the gio-2.0 library.

The Code

#include <freesmartphone.h>
#include <fsoframework.h>
//The GLib mainloop
GMainLoop* ml;

//Callback to list resources
static void list_resources_ready(GObject* source, GAsyncResult* res, gpointer user_data)
{
  FreeSmartphoneUsage* usage = FREE_SMARTPHONE_USAGE(user_data);
  int nr_resources;
  int i;
  GError* error = NULL;
  //Get results
  char** resources = free_smartphone_usage_list_resources_finish(
          usage, res, &nr_resources, &error);
  //Handle error case
  if(error)
  {
      g_debug("list resources: %s", error->message);
  }
  //if no error occured print resources
  else
  {
      for(i=0;i<nr_resources; i++)
      {
          g_debug("resource: %s",resources[i]);
      }
  }
}

//Callback to request a resource
static void request_resource_ready(GObject* source, GAsyncResult* res, gpointer user_data)
{
  FreeSmartphoneUsage* usage = FREE_SMARTPHONE_USAGE(user_data);
  GError* e = NULL;
  free_smartphone_usage_request_resource_finish(
          usage, res, &e);
  //Handle error case
  if(e)
  {
      g_debug("request resource: %s", e->message);
  }
  else
       g_debug("success!");
}

//Callback to release a resource
static void release_resource_ready(GObject* source, GAsyncResult* res, gpointer user_data)
{
  FreeSmartphoneUsage* usage = FREE_SMARTPHONE_USAGE(user_data);
  GError* e = NULL;
  free_smartphone_usage_release_resource_finish(
          usage, res, &e);
  //Handle error case
  if(e)
  {
      g_debug("release resource: %s", e->message);
  }
  else
       g_debug("success!");
}

//Signal callback
static gboolean on_resource_changed(GObject* source, char* name, gboolean state, GHashTable* prop, gpointer user_data)
{
  //print state
  g_debug("resource changed: %s %s", name, state ? "true": "false");
  //quit the mainloop to get a clean exit
  if(!state)
       g_main_loop_quit(ml);
  return FALSE;
}

int main(int argc, char* argv[])
{
  //get the mainloop
  ml = g_main_loop_new(NULL, FALSE);
  GError* error = NULL;

  //Get the dbus connection. ATM everything lives on system bus
  DBusGConnection* con = dbus_g_bus_get(DBUS_BUS_SYSTEM, &error);
  if(error)
  {
  }
  //Get the usage object
  FreeSmartphoneUsage* usage = free_smartphone_get_usage_proxy(con,
              FSO_FRAMEWORK_USAGE_ServiceDBusName,
              FSO_FRAMEWORK_USAGE_ServicePathPrefix);

   //connect a signal handle to "resource-changed"-signal
   g_signal_connect(usage, "resource-changed", G_CALLBACK(on_resource_changed), usage);

   //start the async call to list resources
   free_smartphone_usage_list_resources(usage, (GAsyncReadyCallback)list_resources_ready, usage); 

   //request the Display resource
   free_smartphone_usage_request_resource(usage, "Display", (GAsyncReadyCallback)request_resource_ready, usage);
   //request a bogus resource to force the error case
   free_smartphone_usage_request_resource(usage, "BOGUS", (GAsyncReadyCallback)request_resource_ready, usage);
   //release the Display resource
   free_smartphone_usage_release_resource(usage, "Display", (GAsyncReadyCallback)release_resource_ready, usage);

   //start the mainloop
   g_main_loop_run(ml); 

   g_debug("returned from mainloop");
   //free memory
   dbus_g_connection_unref(con);
   g_object_unref(G_OBJECT(usage));
   g_main_loop_unref(ml); 

   return 0;
}

How to compile

gcc -Wall $(pkg-config --cflags --libs fso-glib-1.0 fsoframework-2.0) -o fsoresource fsoresource.c