module-gsettings: new module to store configuration using gsettings

GConf is deprecated, and distributions are removing it. paprefs depends
on GConf, so in order to avoid paprefs getting removed as well, paprefs
has to be changed to use something else than GConf. GSettings is the
easiest alternative to migrate to, although it has the same problems
that GConf had: no support for system mode or networking.

This patch takes the non-GConf specific code from module-gconf and puts
it in stdin-util.[ch], which is then reused by module-gsettings.
module-gsettings is designed to be very similar to module-gconf.

Migration is expected to happen as follows: Distributions update
PulseAudio and paprefs at the same time, or first PulseAudio and then
paprefs. paprefs depends on module-gsettings, and module-gsettings
conflicts with module-gconf. Therefore module-gconf gets automatically
removed during the paprefs update. After the update an old PulseAudio is
likely to be running with module-gconf loaded. If the user tries to use
paprefs during this period, whatever the user does in paprefs won't have
any effect until PulseAudio is restarted (probably by a reboot or
relogin). This is not ideal, but will have to do.

When module-gsettings is loaded, it runs gsettings-data-convert
(implemented in a later patch). That will copy the settings from GConf
to GSettings. If gsettings-data-convert is not available (it's part of
GConf, so it may have already been uninstalled), then any previous
paprefs settings are lost.

src/modules/gsettings/module-gsettings.c

@@ -0,0 +1,110 @@
+/***
+  This file is part of PulseAudio.
+
+  Copyright 2006 Lennart Poettering
+
+  PulseAudio is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Lesser General Public License as published
+  by the Free Software Foundation; either version 2.1 of the License,
+  or (at your option) any later version.
+
+  PulseAudio is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with PulseAudio; if not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "../stdin-util.h"
+
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include <pulsecore/core-error.h>
+#include <pulsecore/core-util.h>
+#include <pulsecore/start-child.h>
+
+PA_MODULE_AUTHOR("Sylvain Baubeau");
+PA_MODULE_DESCRIPTION("GSettings Adapter");
+PA_MODULE_VERSION(PACKAGE_VERSION);
+PA_MODULE_LOAD_ONCE(true);
+
+int pa__init(pa_module*m) {
+    struct userdata *u;
+    int r;
+
+    u = pa_xnew(struct userdata, 1);
+    u->core = m->core;
+    u->module = m;
+    m->userdata = u;
+    u->module_infos = pa_hashmap_new_full(pa_idxset_string_hash_func, pa_idxset_string_compare_func, NULL, (pa_free_cb_t) module_info_free);
+    u->pid = (pid_t) -1;
+    u->fd = -1;
+    u->fd_type = 0;
+    u->io_event = NULL;
+    u->buf_fill = 0;
+
+    if ((u->fd = pa_start_child_for_read(
+#if defined(__linux__) && !defined(__OPTIMIZE__)
+                              pa_run_from_build_tree() ? PA_BUILDDIR "/gsettings-helper" :
+#endif
+                 PA_GSETTINGS_HELPER, NULL, &u->pid)) < 0)
+        goto fail;
+
+    u->io_event = m->core->mainloop->io_new(
+            m->core->mainloop,
+            u->fd,
+            PA_IO_EVENT_INPUT,
+            io_event_cb,
+            u);
+
+    do {
+        if ((r = handle_event(u)) < 0)
+            goto fail;
+
+        /* Read until the client signalled us that it is ready with
+         * initialization */
+    } while (r != 1);
+
+    return 0;
+
+fail:
+    pa__done(m);
+    return -1;
+}
+
+void pa__done(pa_module*m) {
+    struct userdata *u;
+
+    pa_assert(m);
+
+    if (!(u = m->userdata))
+        return;
+
+    if (u->pid != (pid_t) -1) {
+        kill(u->pid, SIGTERM);
+
+        for (;;) {
+            if (waitpid(u->pid, NULL, 0) >= 0)
+                break;
+
+            if (errno != EINTR) {
+                pa_log("waitpid() failed: %s", pa_cstrerror(errno));
+                break;
+            }
+        }
+    }
+
+    if (u->io_event)
+        m->core->mainloop->io_free(u->io_event);
+
+    if (u->fd >= 0)
+        pa_close(u->fd);
+
+    if (u->module_infos)
+        pa_hashmap_free(u->module_infos);
+
+    pa_xfree(u);
+}