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-rw-r--r--doc/writing-afb-plugins.md107
1 files changed, 96 insertions, 11 deletions
diff --git a/doc/writing-afb-plugins.md b/doc/writing-afb-plugins.md
index f0e3a376..ba2e676a 100644
--- a/doc/writing-afb-plugins.md
+++ b/doc/writing-afb-plugins.md
@@ -1,7 +1,7 @@
HOWTO WRITE a PLUGIN for AFB-DAEMON
===================================
version: 1
- Date: 24 mai 2016
+ Date: 25 May 2016
Author: José Bollo
TABLE-OF-CONTENT-HERE
@@ -295,7 +295,20 @@ Here is its listing:
}
This examples show many aspects of writing a synchronous
-verb implementation.
+verb implementation. Let summarize it:
+
+1. The function **board_of_req** retrieves the context stored
+for the plugin: the board.
+
+2. The macro **INFO** sends a message of kind *INFO*
+to the logging system. The global variable named **afbitf**
+used represents the interface to afb-daemon.
+
+3. The function **describe** creates a json_object representing
+the board.
+
+4. The function **afb_req_success** sends the reply, attaching to
+it the object *description*.
### The incoming request
@@ -358,10 +371,10 @@ its context: the board. This function is *board_of_req*:
return afb_req_context(req, (void*)get_new_board, (void*)release_board);
}
-This function is very simple because it merely wraps
-a call to the function **afb_req_context**, providing
-all needed arguments.
-The casts are required to avoid a warning when compiling.
+The function **afb_req_context** ensure an existing context
+for the session of the request.
+Its two last arguments are functions. Here, the casts are required
+to avoid a warning when compiling.
Here is the definition of the function **afb_req_context**
@@ -382,23 +395,95 @@ Here is the definition of the function **afb_req_context**
return result;
}
-This powerful function ensures that the context exists and is
-stored for the session.
-
+The second argument if the function that creates the context.
+For the plugin *tic-tac-toe* it is the function **get_new_board**.
The function **get_new_board** creates a new board and set its
count of use to 1. The boards are counting their count of use
to free there ressources when no more used.
-The function **release_board**
+The third argument if the function that frees the context.
+For the plugin *tic-tac-toe* it is the function **release_board**.
+The function **release_board** decrease the the count of use of
+the board given as argument. If the use count decrease to zero,
+the board data are freed.
### Sending the reply to a request
+Sending a reply to a request must be done at most one time.
+
+Two kinds of replies can be made: successful replies and
+failure replies.
+
+The functions to send replies are defined as below:
+
+ /*
+ * Sends a reply of kind success to the request 'req'.
+ * The status of the reply is automatically set to "success".
+ * Its send the object 'obj' (can be NULL) with an
+ * informationnal comment 'info (can also be NULL).
+ */
+ static inline void afb_req_success(struct afb_req req, struct json_object *obj, const char *info)
+ {
+ req.itf->success(req.closure, obj, info);
+ }
+
+ /*
+ * Same as 'afb_req_success' but the 'info' is a formatting
+ * string followed by arguments.
+ */
+ static inline void afb_req_success_f(struct afb_req req, struct json_object *obj, const char *info, ...)
+ {
+ char *message;
+ va_list args;
+ va_start(args, info);
+ if (info == NULL || vasprintf(&message, info, args) < 0)
+ message = NULL;
+ va_end(args);
+ afb_req_success(req, obj, message);
+ free(message);
+ }
+
+ /*
+ * Sends a reply of kind failure to the request 'req'.
+ * The status of the reply is set to 'status' and an
+ * informationnal comment 'info' (can also be NULL) can be added.
+ *
+ * Note that calling afb_req_fail("success", info) is equivalent
+ * to call afb_req_success(NULL, info). Thus even if possible it
+ * is strongly recommanded to NEVER use "success" for status.
+ */
+ static inline void afb_req_fail(struct afb_req req, const char *status, const char *info)
+ {
+ req.itf->fail(req.closure, status, info);
+ }
+
+ /*
+ * Same as 'afb_req_fail' but the 'info' is a formatting
+ * string followed by arguments.
+ */
+ static inline void afb_req_fail_f(struct afb_req req, const char *status, const char *info, ...)
+ {
+ char *message;
+ va_list args;
+ va_start(args, info);
+ if (info == NULL || vasprintf(&message, info, args) < 0)
+ message = NULL;
+ va_end(args);
+ afb_req_fail(req, status, message);
+ free(message);
+ }
+
+
+
Getting argument of invocation
------------------------------
+Sending messages to the log system
+----------------------------------
+
How to build a plugin
---------------------
-Afb-daemon provides a The packaging of afb-daemon
+Afb-daemon provides a *pkg-config* configuration file.