varlink: add varlink_many_*() helpers that send messages to a set of connections at once

If we have a Varlink interface that allows man subscribers to the same
source of events we typically want to notify all of them at once with
the same message.

Let's add some helpers for this purpose: varlink_many_*() can be used to
send messages, similar to the corresponding varlink_*() calls, but they
take a Set of Varlink objects and we issue the operation on every
connection once.

This ports over one existing case where this is beneficial, but the main
user for this is supposed to be importd later.

1 files changed, 8 insertions, 1 deletions

diff --git a/src/shared/varlink.h b/src/shared/varlink.h
index 739786b975..40a8fd086f 100644
--- a/src/shared/varlink.h
+++ b/src/shared/varlink.h
@@ -2,9 +2,10 @@
 #pragma once
 
 #include "sd-event.h"
-
 #include "sd-json.h"
+
 #include "pidref.h"
+#include "set.h"
 #include "time-util.h"
 #include "varlink-idl.h"
 
@@ -264,6 +265,12 @@ int varlink_invocation(VarlinkInvocationFlags flags);
 
 int varlink_error_to_errno(const char *error, sd_json_variant *parameters);
 
+int varlink_many_notifyb(Set *s, ...);
+#define varlink_many_notifybo(s, ...)                           \
+        varlink_many_notifyb((s), SD_JSON_BUILD_OBJECT(__VA_ARGS__))
+int varlink_many_reply(Set *s, sd_json_variant *parameters);
+int varlink_many_error(Set *s, const char *error_id, sd_json_variant *parameters);
+
 DEFINE_TRIVIAL_CLEANUP_FUNC(Varlink *, varlink_unref);
 DEFINE_TRIVIAL_CLEANUP_FUNC(Varlink *, varlink_close_unref);
 DEFINE_TRIVIAL_CLEANUP_FUNC(Varlink *, varlink_flush_close_unref);