add (empty for now) monitoring hook

misc.c

@@ -21,3 +21,13 @@ char *bindump(char *buf, long buflen)
 	}
 	return (utstring_body(out));
 }
+
+/*
+ * At each received message, the recorder invokes this function with the
+ * current epoch time and the topic being handled. Use this to update
+ * a monitoring hoook.
+ */
+
+void monitorhook(time_t now, char *topic)
+{
+}

misc.h

@@ -1 +1,8 @@
+#ifndef MISC_H_INCLUDED
+# define MISC_H_INCLUDED
+
+#include <time.h>
 char *bindump(char *buf, long buflen);
+void monitorhook(time_t now, char *topic);
+
+#endif

ot-recorder.c

@@ -388,6 +388,8 @@ void on_message(struct mosquitto *mosq, void *userdata, const struct mosquitto_m
 
 	time(&now);
 
+	monitorhook(now, m->topic);
+
 	/* FIXME: handle null leading topic `/` */
 	utstring_printf(basetopic, "%s/%s/%s", topics[0], topics[1], topics[2]);
 	utstring_printf(username, "%s", topics[1]);