man: add sample glib/sd-event integration

This should be moved to man pages, but for now the C code is included directly.

Suggested by Zbyszek.

man/glib-event-glue.c

@@ -0,0 +1,74 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  Copyright 2014 Tom Gundersen
+
+  Permission is hereby granted, free of charge, to any person
+  obtaining a copy of this software and associated documentation files
+  (the "Software"), to deal in the Software without restriction,
+  including without limitation the rights to use, copy, modify, merge,
+  publish, distribute, sublicense, and/or sell copies of the Software,
+  and to permit persons to whom the Software is furnished to do so,
+  subject to the following conditions:
+
+  The above copyright notice and this permission notice shall be
+  included in all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+  BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+  ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+***/
+
+#include <assert.h>
+#include <errno.h>
+#include <stdlib.h>
+
+#include "glib-event-glue.h"
+
+typedef struct SDEventSource {
+        GSource source;
+        GPollFD pollfd;
+        sd_event *event;
+} SDEventSource;
+
+static gboolean event_prepare(GSource *source, gint *timeout_) {
+        return sd_event_prepare(((SDEventSource *)source)->event) > 0;
+}
+
+static gboolean event_check(GSource *source) {
+        return sd_event_wait(((SDEventSource *)source)->event, 0) > 0;
+}
+
+static gboolean event_dispatch(GSource *source, GSourceFunc callback, gpointer user_data) {
+        return sd_event_dispatch(((SDEventSource *)source)->event) > 0;
+}
+
+static void event_finalize(GSource *source) {
+        sd_event_unref(((SDEventSource *)source)->event);
+}
+
+static GSourceFuncs event_funcs = {
+        .prepare = event_prepare,
+        .check = event_check,
+        .dispatch = event_dispatch,
+        .finalize = event_finalize,
+};
+
+GSource *g_sd_event_create_source(sd_event *event) {
+        SDEventSource *source;
+
+        source = (SDEventSource *)g_source_new(&event_funcs, sizeof(SDEventSource));
+
+        source->event = sd_event_ref(event);
+        source->pollfd.fd = sd_event_get_fd(event);
+        source->pollfd.events = G_IO_IN | G_IO_HUP | G_IO_ERR;
+
+        g_source_add_poll((GSource *)source, &source->pollfd);
+
+        return (GSource *)source;
+}