ircd:Ⓜ️ Preliminary efficient membership query object.

include/ircd/m/room.h

@@ -39,6 +39,7 @@ struct ircd::m::room
 	struct alias;
 	struct events;
 	struct state;
+	struct members;
 
 	using id = m::id::room;
 
@@ -95,3 +96,20 @@ struct ircd::m::room::state
 	:room_id{room.room_id}
 	{}
 };
+
+struct ircd::m::room::members
+:m::events
+{
+	id room_id;
+
+	bool _query_(const event::where &, const event_closure_bool &) const override;
+	bool _rquery_(const event::where &, const event_closure_bool &) const override;
+
+	members(const id &room_id)
+	:room_id{room_id}
+	{}
+
+	members(const room &room)
+	:room_id{room.room_id}
+	{}
+};

ircd/matrix.cc

@@ -397,6 +397,74 @@ ircd::m::room::send(json::iov &event)
 	return generated_event_id;
 }
 
+bool
+ircd::m::room::members::_rquery_(const event::where &where,
+                                 const event_closure_bool &closure)
+const
+{
+	event::cursor cursor
+	{
+		"event_id for type,state_key in room_id",
+		&where
+	};
+
+	//TODO: ???
+	static const size_t max_type_size
+	{
+		256
+	};
+
+	const auto key_max
+	{
+		room::id::buf::SIZE + max_type_size
+	};
+
+	size_t key_len;
+	char key[key_max]; key[0] = '\0';
+	key_len = strlcat(key, room_id, sizeof(key));
+	key_len = strlcat(key, "..m.room.member", sizeof(key)); //TODO: prefix protocol
+
+	for(auto it(cursor.rbegin(key)); bool(it); ++it)
+		if(closure(*it))
+			return true;
+
+	return false;
+}
+
+bool
+ircd::m::room::members::_query_(const event::where &where,
+                                const event_closure_bool &closure)
+const
+{
+	event::cursor cursor
+	{
+		"event_id for type,state_key in room_id",
+		&where
+	};
+
+	//TODO: ???
+	static const size_t max_type_size
+	{
+		256
+	};
+
+	const auto key_max
+	{
+		room::id::buf::SIZE + max_type_size
+	};
+
+	size_t key_len;
+	char key[key_max]; key[0] = '\0';
+	key_len = strlcat(key, room_id, sizeof(key));
+	key_len = strlcat(key, "..m.room.member", sizeof(key)); //TODO: prefix protocol
+
+	for(auto it(cursor.begin(key)); bool(it); ++it)
+		if(closure(*it))
+			return true;
+
+	return false;
+}
+
 bool
 ircd::m::room::state::_rquery_(const event::where &where,
                                const event_closure_bool &closure)