Properly unsubscribe any module from a topic when it gets deregistere…

…d. Updated readme with small libmodule example.

Lib/pubsub.c

@@ -10,6 +10,7 @@ static void destroy_pubsub_msg(pubsub_priv_t *pubsub_msg);
 static module_ret_code tell_pubsub_msg(pubsub_priv_t *m, module *mod, m_context *c);
 static module_ret_code publish_msg(const module *mod, const char *topic, const unsigned char *message, 
                                    const ssize_t size, const bool autofree);
+static map_ret_code unsubscribe(void *data, const char *key, void *value);
 
 static map_ret_code tell_if(void *data, const char *key, void *value) {
     module *mod = (module *)value;
@@ -90,6 +91,16 @@ static module_ret_code publish_msg(const module *mod, const char *topic, const u
     return MOD_ERR;
 }
 
+static map_ret_code unsubscribe(void *data, const char *key, void *value) {
+    module *mod = (module *)value;
+    const char *topic = (const char *)data;
+
+    if (map_has_key(mod->subscriptions, topic)) {
+        map_remove(mod->subscriptions, topic);
+    }
+    return MAP_OK;
+}
+
 /** Private API **/
 
 module_ret_code tell_system_pubsub_msg(m_context *c, enum msg_type type, const self_t *sender, const char *topic) {
@@ -169,6 +180,8 @@ module_ret_code module_deregister_topic(const self_t *self, const char *topic) {
     /* Only same mod which registered topic can deregister it */
     if (tmp == mod) {
         if (map_remove(c->topics, topic) == MAP_OK) {
+            /* Automatically unsubscribe any module subscribed to topic */
+            map_iterate(c->modules, unsubscribe, (void *)topic);
             tell_system_pubsub_msg(c, TOPIC_DEREGISTERED, self, topic);
             return MOD_OK;
         }

README.md

@@ -14,6 +14,63 @@ Indeed, libmodule was heavily inspired by my own actor library experience with [
 
 Unsurprisingly, module is the core concept of libmodule architecture.  
 A module is an Actor that can listen on socket events too.  
+Frankly speaking, it is denoted by a MODULE() macro plus a bunch of callbacks, eg:
+```
+cat pippo.c
+
+#include <module/module_easy.h>
+#include <module/modules_easy.h>
+#include <string.h>
+#include <ctype.h>
+
+MODULE("Foo");
+
+static void init(void) {
+    m_register_fd(STDIN_FILENO, 0, NULL);
+}
+
+static bool check(void) {
+    return true;
+}
+
+static bool evaluate(void) {
+    return true;
+}
+
+static void destroy(void) {
+    
+}
+
+static void receive(const msg_t *msg, const void *userdata) {
+    if (!msg->is_pubsub) {
+        char c;
+        read(msg->fd_msg->fd, &c, sizeof(char));
+        switch (tolower(c)) {
+            case 'q':
+                m_log("Leaving...\n");
+                m_tell(self(), "ByeBye");
+                break;
+            default:
+                m_log("Pressed %c\n", c);
+                break;
+        }
+    } else if (msg->pubsub_msg->type == USER && 
+        !strcmp((char *)msg->pubsub_msg->message, "ByeBye")) {
+            
+        modules_quit(0);
+    }
+}
+```
+```
+cat main.c
+
+#include <module/modules_easy.h>
+
+int main() {
+    return modules_loop();
+}
+```
+In this example, a "Foo" module is created and will read chars from stdin until 'q' is pressed.
 
 ## Is it portable?
 

Samples/Easy/pippo.c

@@ -118,13 +118,13 @@ static void receive(const msg_t *msg, const void *userdata) {
                 }
                 break;
         }
-    } else {
-        if (msg->pubsub_msg->type == USER && !strcmp((char *)msg->pubsub_msg->message, "BauBau")) {
-            m_become(ready);
-            /* Finally register Leaving topic */
-            m_register_topic("leaving");
-            m_log("Press 'p' to play with Doggo! Or 'f' to feed your Doggo. 's' to have a nap. 'w' to wake him up. 'q' to leave him for now.\n");
-        }
+    } else if (msg->pubsub_msg->type == USER && 
+        !strcmp((char *)msg->pubsub_msg->message, "BauBau")) {
+
+        m_become(ready);
+        /* Finally register Leaving topic */
+        m_register_topic("leaving");
+        m_log("Press 'p' to play with Doggo! Or 'f' to feed your Doggo. 's' to have a nap. 'w' to wake him up. 'q' to leave him for now.\n");
     }
 }
 

TODO.md

@@ -13,6 +13,7 @@
 - [x] Avoid telling system messages like MODULE_STARTED/TOPIC_REGISTERED to ourselves
 - [x] Test pubsub messagging for paused modules
 - [x] Fix memleaks!
+- [x] Unsubscribe every module when a topic gets deregistered
 
 ### Generic
 - [x] Add some diagnostic API, eg: module_dump() (to dump each module's state)
@@ -30,6 +31,7 @@
 - [x] module_tell/publish/broadcast
 - [x] MODULE_STARTED/MODULE_STOPPED new sysmessages
 - [x] Avoid telling system messages like MODULE_STARTED/TOPIC_REGISTERED to ourselves
+- [ ] Add doc for new deregister_topic behaviour (ie: it automatically unsubscribes any module subscribed)
 - [ ] Add a new page about trusting pointers
 
 ### Samples
@@ -38,6 +40,7 @@
 ### Test
 - [x] Fix tests
 - [x] add module_dump tests
+- [ ] Add test to new deregister_topic behaviour (ie: it automatically unsubscribes any module subscribed)
 
 ## 5.1.0