bus: add convenience functions for constructing and sending method calls/signals in one call

src/journal/journal-gatewayd.c

@@ -743,7 +743,7 @@ static int request_handler_file(
 }
 
 static int get_virtualization(char **v) {
-        _cleanup_bus_message_unref_ sd_bus_message *m = NULL, *reply = NULL;
+        _cleanup_bus_message_unref_ sd_bus_message *reply = NULL;
         _cleanup_bus_unref_ sd_bus *bus = NULL;
         const char *t;
         char *b;
@@ -753,21 +753,17 @@ static int get_virtualization(char **v) {
         if (r < 0)
                 return r;
 
-        r = sd_bus_message_new_method_call(
+        r = sd_bus_call_method(
                         bus,
                         "org.freedesktop.systemd1",
                         "/org/freedesktop/systemd1",
                         "org.freedesktop.DBus.Properties",
                         "Get",
-                        &m);
+                        NULL,
-        if (r < 0)
+                        &reply,
-                return r;
+                        "ss",
-
+                        "org.freedesktop.systemd1.Manager",
-        r = sd_bus_message_append(m, "ss", "org.freedesktop.systemd1.Manager", "Virtualization");
+                        "Virtualization");
-        if (r < 0)
-                return r;
-
-        r = sd_bus_send_with_reply_and_block(bus, m, 0, NULL, &reply);
         if (r < 0)
                 return r;
 

src/libsystemd-bus/bus-message.c

@@ -1241,7 +1241,7 @@ int sd_bus_message_close_container(sd_bus_message *m) {
         return 0;
 }
 
-static int message_append_ap(
+int bus_message_append_ap(
                 sd_bus_message *m,
                 const char *types,
                 va_list ap) {
@@ -1327,7 +1327,7 @@ static int message_append_ap(
 
                                 n = va_arg(ap, unsigned);
                                 for (i = 0; i < n; i++) {
-                                        r = message_append_ap(m, s, ap);
+                                        r = bus_message_append_ap(m, s, ap);
                                         if (r < 0)
                                                 return r;
                                 }
@@ -1349,7 +1349,7 @@ static int message_append_ap(
                         if (r < 0)
                                 return r;
 
-                        r = message_append_ap(m, s, ap);
+                        r = bus_message_append_ap(m, s, ap);
                         if (r < 0)
                                 return r;
 
@@ -1377,7 +1377,7 @@ static int message_append_ap(
 
                                 t += k - 1;
 
-                                r = message_append_ap(m, s, ap);
+                                r = bus_message_append_ap(m, s, ap);
                                 if (r < 0)
                                         return r;
 
@@ -1407,10 +1407,10 @@ int sd_bus_message_append(sd_bus_message *m, const char *types, ...) {
         if (m->sealed)
                 return -EPERM;
         if (!types)
-                return -EINVAL;
+                return 0;
 
         va_start(ap, types);
-        r = message_append_ap(m, types, ap);
+        r = bus_message_append_ap(m, types, ap);
         va_end(ap);
 
         return r;

src/libsystemd-bus/bus-message.h

@@ -144,3 +144,5 @@ int bus_message_from_malloc(
                 sd_bus_message **ret);
 
 const char* bus_message_get_arg(sd_bus_message *m, unsigned i);
+
+int bus_message_append_ap(sd_bus_message *m, const char *types, va_list ap);

src/libsystemd-bus/sd-bus.c

@@ -2208,3 +2208,60 @@ int sd_bus_remove_match(sd_bus *bus, const char *match, sd_bus_message_handler_t
                 return r;
         return q;
 }
+
+int sd_bus_emit_signal(
+                sd_bus *bus,
+                const char *path,
+                const char *interface,
+                const char *member,
+                const char *types, ...) {
+
+        _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
+        va_list ap;
+        int r;
+
+        if (!bus)
+                return -EINVAL;
+
+        r = sd_bus_message_new_signal(bus, path, interface, member, &m);
+        if (r < 0)
+                return r;
+
+        va_start(ap, types);
+        r = bus_message_append_ap(m, types, ap);
+        va_end(ap);
+        if (r < 0)
+                return r;
+
+        return sd_bus_send(bus, m, NULL);
+}
+
+int sd_bus_call_method(
+                sd_bus *bus,
+                const char *destination,
+                const char *path,
+                const char *interface,
+                const char *member,
+                sd_bus_error *error,
+                sd_bus_message **reply,
+                const char *types, ...) {
+
+        _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
+        va_list ap;
+        int r;
+
+        if (!bus)
+                return -EINVAL;
+
+        r = sd_bus_message_new_method_call(bus, destination, path, interface, member, &m);
+        if (r < 0)
+                return r;
+
+        va_start(ap, types);
+        r = bus_message_append_ap(m, types, ap);
+        va_end(ap);
+        if (r < 0)
+                return r;
+
+        return sd_bus_send_with_reply_and_block(bus, m, 0, error, reply);
+}

src/systemd/sd-bus.h

@@ -145,6 +145,11 @@ int sd_bus_message_exit_container(sd_bus_message *m);
 int sd_bus_message_peek_type(sd_bus_message *m, char *type, const char **contents);
 int sd_bus_message_rewind(sd_bus_message *m, int complete);
 
+/* Convenience calls */
+
+int sd_bus_emit_signal(sd_bus *bus, const char *path, const char *interface, const char *member, const char *types, ...);
+int sd_bus_call_method(sd_bus *bus, const char *destination, const char *path, const char *interface, const char *member, sd_bus_error *error, sd_bus_message **reply, const char *types, ...);
+
 /* Bus management */
 
 int sd_bus_get_unique_name(sd_bus *bus, const char **unique);