Events: refactoring

This new version allows to subscribe a client for
an event.

The event should first be created for the API
(the API's prefix is added) using 'afb_daemon_make_event'.

After that, plugins can subscribe or unsubscribe their
clients (identified through requests) to the events that
it generates. See 'afb_req_subscribe' and 'afb_req_unsubscribe'.

Events created by 'afb_daemon_make_event' can be widely
broadcasted using 'afb_event_broadcast' or pushed only to
suscribers using 'afb_event_push'.

Events can be destroyed using 'afb_event_drop'.

Change-Id: I7c0bed5e625c2052dcd81c6bfe960def1fa032f3
Signed-off-by: José Bollo <jose.bollo@iot.bzh>

3 files changed, 127 insertions, 2 deletions

diff --git a/include/afb/afb-event-itf.h b/include/afb/afb-event-itf.h
new file mode 100644
index 00000000..47ffa387
--- /dev/null
+++ b/include/afb/afb-event-itf.h
@@ -0,0 +1,84 @@
+/*
+ * Copyright (C) 2016 "IoT.bzh"
+ * Author: José Bollo <jose.bollo@iot.bzh>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+/* avoid inclusion of <json-c/json.h> */
+struct json_object;
+
+/*
+ * Interface for handling requests.
+ * It records the functions to be called for the request.
+ * Don't use this structure directly.
+ * Use the helper functions documented below.
+ */ 
+struct afb_event_itf {
+	/* CAUTION: respect the order, add at the end */
+
+	int (*broadcast)(void *closure, struct json_object *obj);
+	int (*push)(void *closure, struct json_object *obj);
+	void (*drop)(void *closure);
+};
+
+/*
+ * Describes the request by plugins from afb-daemon
+ */
+struct afb_event {
+	const struct afb_event_itf *itf;	/* the interface to use */
+	void *closure;				/* the closure argument for functions of 'itf' */
+};
+
+/*
+ * Broadcasts widely the 'event' with the data 'object'.
+ * 'object' can be NULL.
+ *
+ * For conveniency, the function calls 'json_object_put' for 'object'.
+ * Thus, in the case where 'object' should remain available after
+ * the function returns, the function 'json_object_get' shall be used.
+ *
+ * Returns the count of clients that received the event.
+ */
+static inline int afb_event_broadcast(struct afb_event event, struct json_object *object)
+{
+	return event.itf->broadcast(event.closure, object);
+}
+
+/*
+ * Pushes the 'event' with the data 'object' to its obeservers.
+ * 'object' can be NULL.
+ *
+ * For conveniency, the function calls 'json_object_put' for 'object'.
+ * Thus, in the case where 'object' should remain available after
+ * the function returns, the function 'json_object_get' shall be used.
+ *
+ * Returns the count of clients that received the event.
+ */
+static inline int afb_event_push(struct afb_event event, struct json_object *object)
+{
+	return event.itf->push(event.closure, object);
+}
+
+/*
+ * Drops the data associated to the event
+ * After calling this function, the event
+ * MUST NOT BE USED ANYMORE.
+ */
+static inline void afb_event_drop(struct afb_event event)
+{
+	event.itf->drop(event.closure);
+}
+
diff --git a/include/afb/afb-plugin.h b/include/afb/afb-plugin.h
index 1eb3475b..85e8de7e 100644
--- a/include/afb/afb-plugin.h
+++ b/include/afb/afb-plugin.h
@@ -38,6 +38,7 @@
  * Some function of the library are exported to afb-daemon.
  */
 
+#include <afb/afb-event-itf.h>
 #include <afb/afb-req-itf.h>
 
 /*
@@ -140,11 +141,12 @@ struct sd_bus;
  * Definition of the facilities provided by the daemon.
  */
 struct afb_daemon_itf {
-       void (*event_broadcast)(void *closure, const char *name, struct json_object *object); /* broadcasts evant 'name' with 'object' */
+       int (*event_broadcast)(void *closure, const char *name, struct json_object *object); /* broadcasts evant 'name' with 'object' */
        struct sd_event *(*get_event_loop)(void *closure);      /* gets the common systemd's event loop */
        struct sd_bus *(*get_user_bus)(void *closure);          /* gets the common systemd's user d-bus */
        struct sd_bus *(*get_system_bus)(void *closure);        /* gets the common systemd's system d-bus */
        void (*vverbose)(void*closure, int level, const char *file, int line, const char *fmt, va_list args);
+       struct afb_event (*event_make)(void *closure, const char *name); /* creates an event of 'name' */
 };
 
 /*
@@ -206,13 +208,24 @@ static inline struct sd_bus *afb_daemon_get_system_bus(struct afb_daemon daemon)
  * For conveniency, the function calls 'json_object_put' for 'object'.
  * Thus, in the case where 'object' should remain available after
  * the function returns, the function 'json_object_get' shall be used.
+ *
+ * Returns the count of clients that received the event.
  */
-static inline void afb_daemon_broadcast_event(struct afb_daemon daemon, const char *name, struct json_object *object)
+static inline int afb_daemon_broadcast_event(struct afb_daemon daemon, const char *name, struct json_object *object)
 {
 	return daemon.itf->event_broadcast(daemon.closure, name, object);
 }
 
 /*
+ * Creates an event of 'name' and returns it.
+ * 'daemon' MUST be the daemon given in interface when activating the plugin.
+ */
+static inline struct afb_event afb_daemon_make_event(struct afb_daemon daemon, const char *name)
+{
+	return daemon.itf->event_make(daemon.closure, name);
+}
+
+/*
  * Send a message described by 'fmt' and following parameters
  * to the journal for the verbosity 'level'.
  * 'file' and 'line' are indicators of position of the code in source files.
diff --git a/include/afb/afb-req-itf.h b/include/afb/afb-req-itf.h
index f4fab551..2b3bc467 100644
--- a/include/afb/afb-req-itf.h
+++ b/include/afb/afb-req-itf.h
@@ -25,6 +25,8 @@
 #include <stdarg.h>
 #include <stdio.h>
 
+#include <afb/afb-event-itf.h>
+
 /* avoid inclusion of <json-c/json.h> */
 struct json_object;
 
@@ -65,6 +67,9 @@ struct afb_req_itf {
 
 	void (*session_close)(void *closure);
 	int (*session_set_LOA)(void *closure, unsigned level);
+
+	int (*subscribe)(void *closure, struct afb_event event);
+	int (*unsubscribe)(void *closure, struct afb_event event);
 };
 
 /*
@@ -315,6 +320,29 @@ static inline struct afb_req afb_req_unstore(struct afb_req *req)
 	return result;
 }
 
+/*
+ * Establishes for the client link identified by 'req' a subscription
+ * to the 'event'.
+ * Returns 0 in case of successful subscription or -1 in case of error.
+ */
+static inline int afb_req_subscribe(struct afb_req req, struct afb_event event)
+{
+	return req.itf->subscribe(req.closure, event);
+}
+
+/*
+ * Revokes the subscription established to the 'event' for the client
+ * link identified by 'req'.
+ * Returns 0 in case of successful subscription or -1 in case of error.
+ */
+static inline int afb_req_unsubscribe(struct afb_req req, struct afb_event event)
+{
+	return req.itf->unsubscribe(req.closure, event);
+}
+
+
+
+
 /* internal use */
 static inline const char *afb_req_raw(struct afb_req req, size_t *size)
 {