degesch: unfuck reference counting

We really needed weak references for the name map.

degesch.c

@@ -103,6 +103,9 @@ static struct config_item g_config_table[] =
 static void user_unref (void *p);
 static void channel_unref (void *p);
 
+/// Callback just before a reference counted object is destroyed
+typedef void (*destroy_cb_fn) (void *object, void *user_data);
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
 struct user_channel
@@ -130,12 +133,15 @@ user_channel_destroy (void *p)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
 // We keep references to user information in channels and buffers,
-// as well as in the name lookup table.
+// and weak references in the name lookup table.
 
 struct user
 {
 	size_t ref_count;                   ///< Reference count
 
+	destroy_cb_fn on_destroy;           ///< To remove any weak references
+	void *user_data;                    ///< User data for callbacks
+
 	// TODO: eventually a reference to the server
 
 	char *nickname;                     ///< Literal nickname
@@ -156,6 +162,9 @@ user_new (void)
 static void
 user_destroy (struct user *self)
 {
+	if (self->on_destroy)
+		self->on_destroy (self, self->user_data);
+
 	free (self->nickname);
 	LIST_FOR_EACH (struct user_channel, iter, self->channels)
 		user_channel_destroy (iter);
@@ -212,6 +221,9 @@ struct channel
 {
 	size_t ref_count;                   ///< Reference count
 
+	destroy_cb_fn on_destroy;           ///< To remove any weak references
+	void *user_data;                    ///< User data for callbacks
+
 	// TODO: eventually a reference to the server
 
 	char *name;                         ///< Channel name
@@ -230,9 +242,11 @@ channel_new (void)
 }
 
 static void
-channel_destroy (void *p)
+channel_destroy (struct channel *self)
 {
-	struct channel *self = p;
+	if (self->on_destroy)
+		self->on_destroy (self, self->user_data);
+
 	free (self->name);
 	free (self->mode);
 	free (self->topic);
@@ -409,8 +423,6 @@ struct app_context
 	//   maybe also broadcast all buffers about the disconnection event
 	// TODO: when getting connected again, rejoin all current channels
 
-	// FIXME: these should only have weak references, so that we don't have
-	//   to watch all places where they might get unref-ed
 	struct str_map irc_users;           ///< IRC user data
 	struct str_map irc_channels;        ///< IRC channel data
 	struct str_map irc_buffer_map;      ///< Maps IRC identifiers to buffers
@@ -480,10 +492,8 @@ app_context_init (struct app_context *self)
 	self->irc_ready = false;
 
 	str_map_init (&self->irc_users);
-	self->irc_users.free = user_unref;
 	self->irc_users.key_xfrm = irc_strxfrm;
 	str_map_init (&self->irc_channels);
-	self->irc_channels.free = channel_unref;
 	self->irc_channels.key_xfrm = irc_strxfrm;
 	str_map_init (&self->irc_buffer_map);
 	self->irc_buffer_map.key_xfrm = irc_strxfrm;
@@ -1057,13 +1067,6 @@ buffer_remove (struct app_context *ctx, struct buffer *buffer)
 	}
 #endif // RL_READLINE_VERSION
 
-	// Get rid of the channel, as well as the users,
-	// if the buffer was the last thing keeping them alive
-	if (buffer->channel && buffer->channel->ref_count == 2)
-		str_map_set (&ctx->irc_channels, buffer->channel->name, NULL);
-	if (buffer->user && buffer->user->ref_count == 2)
-		str_map_set (&ctx->irc_users, buffer->user->nickname, NULL);
-
 	// And make sure to unlink the buffer from "irc_buffer_map"
 	if (buffer->channel)
 		str_map_set (&ctx->irc_buffer_map, buffer->channel->name, NULL);
@@ -1284,6 +1287,50 @@ init_buffers (struct app_context *ctx)
 
 // --- Users, channels ---------------------------------------------------------
 
+static void
+irc_user_on_destroy (void *object, void *user_data)
+{
+	struct user *user = object;
+	struct app_context *ctx = user_data;
+	str_map_set (&ctx->irc_users, user->nickname, NULL);
+}
+
+struct user *
+irc_make_user (struct app_context *ctx, char *nickname)
+{
+	hard_assert (!str_map_find (&ctx->irc_users, nickname));
+
+	struct user *user = user_new ();
+	user->on_destroy = irc_user_on_destroy;
+	user->user_data = ctx;
+	user->nickname = nickname;
+	str_map_set (&ctx->irc_users, user->nickname, user);
+	return user;
+}
+
+static void
+irc_channel_on_destroy (void *object, void *user_data)
+{
+	struct channel *channel = object;
+	struct app_context *ctx = user_data;
+	str_map_set (&ctx->irc_channels, channel->name, NULL);
+}
+
+struct channel *
+irc_make_channel (struct app_context *ctx, char *name)
+{
+	hard_assert (!str_map_find (&ctx->irc_channels, name));
+
+	struct channel *channel = channel_new ();
+	channel->on_destroy = irc_channel_on_destroy;
+	channel->user_data = ctx;
+	channel->name = name;
+	channel->mode = xstrdup ("");
+	channel->topic = NULL;
+	str_map_set (&ctx->irc_channels, channel->name, channel);
+	return channel;
+}
+
 // --- Supporting code ---------------------------------------------------------
 
 static char *
@@ -1833,11 +1880,7 @@ irc_handle_join (struct app_context *ctx, const struct irc_message *msg)
 	// We've joined a new channel
 	if (!channel && irc_is_this_us (ctx, msg->prefix))
 	{
-		channel = channel_new ();
+		channel = irc_make_channel (ctx, xstrdup (target));
-		channel->name = xstrdup (target);
-		channel->mode = xstrdup ("");
-		channel->topic = NULL;
-		str_map_set (&ctx->irc_channels, channel->name, channel);
 
 		buffer = buffer_new ();
 		buffer->type = BUFFER_CHANNEL;
@@ -1857,11 +1900,7 @@ irc_handle_join (struct app_context *ctx, const struct irc_message *msg)
 	char *nickname = irc_cut_nickname (msg->prefix);
 	struct user *user = str_map_find (&ctx->irc_users, nickname);
 	if (!user)
-	{
+		user = irc_make_user (ctx, nickname);
-		user = user_new ();
-		user->nickname = nickname;
-		str_map_set (&ctx->irc_users, user->nickname, user);
-	}
 	else
 		free (nickname);
 
@@ -2041,11 +2080,7 @@ irc_handle_privmsg (struct app_context *ctx, const struct irc_message *msg)
 		char *nickname = irc_cut_nickname (msg->prefix);
 		struct user *user = str_map_find (&ctx->irc_users, nickname);
 		if (!user)
-		{
+			user = irc_make_user (ctx, xstrdup (nickname));
-			user = user_new ();
-			user->nickname = xstrdup (nickname);
-			str_map_set (&ctx->irc_users, user->nickname, user);
-		}
 
 		// Open a new buffer for the user
 		buffer = buffer_new ();
@@ -2120,15 +2155,6 @@ irc_handle_quit (struct app_context *ctx, const struct irc_message *msg)
 		LIST_UNLINK (user->channels, iter);
 		user_channel_destroy (iter);
 	}
-
-	// If it's the last reference, there's no reason for the user to stay.
-	// Note that when the user has their own buffer, it still keeps a reference
-	// and we don't have to care about removing them from "irc_buffer_map".
-	if (user->ref_count == 1)
-	{
-		hard_assert (!user->channels);
-		str_map_set (&ctx->irc_users, user->nickname, NULL);
-	}
 }
 
 static void
@@ -2912,10 +2938,7 @@ irc_connect (struct app_context *ctx, struct error **e)
 	irc_send (ctx, "USER %s 8 * :%s", username, realname);
 
 	// XXX: maybe we should wait for the first message from the server
-	ctx->irc_user = user_new ();
+	ctx->irc_user = irc_make_user (ctx, xstrdup (nickname));
-	ctx->irc_user->nickname = xstrdup (nickname);
-	str_map_set (&ctx->irc_users, nickname, user_ref (ctx->irc_user));
-
 	ctx->irc_user_mode = xstrdup ("");
 	ctx->irc_user_host = NULL;
 	return true;