added first version of configurable hook support with a few examples

TODO: this is not tested yet

git-svn-id: https://zerberus.eonerc.rwth-aachen.de:8443/svn/s2ss/trunk@177 8ec27952-4edc-4aab-86aa-e87bb2611832

server/Makefile

@@ -5,7 +5,7 @@ SRCS = server.c send.c receive.c random.c node.c path.c utils.c msg.c cfg.c if.c
 all: $(TARGETS)
 
 # Dependencies for individual binaries
-server: node.o msg.o utils.o path.o cfg.o if.o tc.o
+server: node.o msg.o utils.o path.o cfg.o if.o tc.o hooks.o
 send: node.o msg.o utils.o
 receive: node.o msg.o utils.o
 random: node.o msg.o utils.o

server/etc/example.conf

@@ -34,6 +34,7 @@ paths = (
 		reverse = true,			# Setup a path in the reverse direction too
 		in = "acs",			# Name of the node we listen to (see above)
 		out = "sintef",			# Name of the node we send to
-		rate = 100			# Send message over this path with a fixed (equalized) rate
+		rate = 100,			# Send message over this path with a fixed (equalized) rate
+		hook = "print"			# Register custom hook funktion (see src/hooks.c)
 	}
 );

server/include/hooks.h

@@ -0,0 +1,60 @@
+/** Hook funktions
+ *
+ * Every path can register a hook function which is called for every received
+ * message. This can be used to debug the data flow, get statistics
+ * or alter the message.
+ *
+ * This file includes some examples.
+ *
+ * @author Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
+ * @copyright 2014, Institute for Automation of Complex Power Systems, EONERC
+ * @file
+ */
+ 
+#ifndef _HOOKS_H_
+#define _HOOKS_H_
+
+struct msg;
+struct path;
+
+/** Callback type of hook function
+ *
+ * @todo Add a way to pass custom data to the hooks
+ * @param m The message which is forwarded
+ * @param p The path which is processing this message.
+ * @retval 0 Success. Continue processing the message.
+ * @retval <0 Error. Drop the message.
+ */
+typedef int (*hook_cb_t)(struct msg *m, struct path *p);
+
+/** This is a static list of available hooks.
+ *
+ * It's used by hook_lookup to parse hook identfiers from the configuration file.
+ * The list must be terminated by NULL pointers!
+ */ 
+struct hook_id {
+	hook_cb_t cb;
+	const char *name;
+};
+
+/** Get a function pointer of a hook function by its name
+ *
+ * @param name The name of the requested hook
+ * @retval NULL There is no hook registred with name.
+ * @retval >0 A function pointer to the requested hook_cb_t hook.
+ */
+hook_cb_t hook_lookup(const char *name);
+
+/** Example hook: Print the message. */
+int hook_print(struct msg *m, struct path *p);
+
+/** Example hook: Filter the message on some criteria. */
+int hook_filter(struct msg *m, struct path *p);
+
+/** Example hook: Convert the message values to fixed precision. */
+int hook_tofixed(struct msg *m, struct path *p);
+
+/** Example hook: Chain multiple hooks */
+int hook_multiple(struct msg *m, struct path *p);
+
+#endif /* _HOOKS_H_ */

server/include/path.h

@@ -14,6 +14,7 @@
 #include "config.h"
 #include "node.h"
 #include "msg.h"
+#include "hooks.h"
 
 /** The datastructure for a path.
  *
@@ -26,12 +27,8 @@ struct path
 	/** Pointer to the outgoing node */
 	struct node *out;
 
-	/** If non NULL this function is called for every received message.
-	 *
-	 * This hook can be used to filter messages on a user-defined criteria.
-	 * If the function has a non-zero return value the message will be dropped.
-	 */
-	int (*hook)(struct msg *m);
+	/** Function pointer of the hook */
+	hook_cb_t hook;
 
 	/** Send messages with a fixed rate over this path */
 	double rate;

server/src/cfg.c

@@ -17,6 +17,7 @@
 #include "node.h"
 #include "path.h"
 #include "utils.h"
+#include "hooks.h"
 
 int config_parse(const char *filename, config_t *cfg, struct settings *set,
 	struct node **nodes, struct path **paths)
@@ -101,6 +102,13 @@ int config_parse_path(config_setting_t *cfg,
 		cerror(cfg, "Invalid output node '%s'", out);
 
 	/* Optional settings */
+	if (config_setting_lookup_string(cfg, "hook", &hook)) {
+		path->hook = hook_lookup(hook);
+		
+		if (!path->hook)
+			cerror(cfg, "Failed to lookup hook function. Not registred?");
+	}
+	
 	config_setting_lookup_bool(cfg, "enabled", &enabled);
 	config_setting_lookup_bool(cfg, "reverse", &reverse);
 	config_setting_lookup_float(cfg, "rate", &path->rate);

server/src/hooks.c

@@ -0,0 +1,72 @@
+/** Hook funktions
+ *
+ * Every path can register a hook function which is called for every received
+ * message. This can be used to debug the data flow, get statistics
+ * or alter the message.
+ *
+ * This file includes some examples.
+ *
+ * @author Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
+ * @copyright 2014, Institute for Automation of Complex Power Systems, EONERC
+ */
+ 
+#include <string.h>
+
+#include "msg.h"
+#include "hooks.h"
+
+/** @todo Make const */
+static struct hook_id hook_list[] = {
+	{ hook_print, "print" },
+	{ hook_filter, "filter" },
+	{ hook_tofixed, "tofixed" },
+	{ hook_multiple, "multiple" },
+	{ NULL }
+};
+
+hook_cb_t hook_lookup(const char *name)
+{
+	for (struct hook_id *hid = hook_list; hid->cb; hid++) {
+		if (!strcmp(name, hid->name)) {
+			return hid->cb;
+		}
+	}
+
+	return NULL; /* No matching hook was found */
+}
+ 
+int hook_print(struct msg *m, struct path *p)
+{
+	/* Print every message once to stdout */
+	msg_fprint(stdout, m);
+
+	return 0;
+}
+
+int hook_filter(struct msg *m, struct path *p)
+{
+	/* Drop every 10th message */
+	if (m->sequence % 10 == 0)
+		return -1;
+	else
+		return 0;
+}
+
+int hook_tofixed(struct msg *m, struct path *p)
+{
+	for (int i=0; i<m->length; i++) {
+		m->data[i].i = m->data[i].f * 1e3; 
+	}
+	
+	return 0;
+}
+
+int hook_multiple(struct msg *m, struct path *p)
+{
+	if (hook_print(m, p))
+		return -1;
+	else if (hook_tofixed(m, p))
+		return -1;
+	else
+		return 0;
+}

server/src/path.c

@@ -108,7 +108,7 @@ static void * path_run(void *arg)
 			continue;
 		}
 
-		if (p->hook && p->hook(m)) {
+		if (p->hook && p->hook(m, p)) {
 			p->skipped++;
 			continue;
 		}