From 864908d48a348c7f690eb72cae88aa09ea4b95cd Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 11 Jun 2023 15:42:25 +0300
Subject: [PATCH] Add string interning to the network protocol

This allows transmitting commonly used strings using short IDs.
---
 source/game/messages.h     |  6 +++++
 source/game/networking.cpp | 54 +++++++++++++++++++++++++++++++++++++-
 source/game/networking.h   | 10 ++++++-
 source/game/protocol.cpp   |  1 +
 4 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/source/game/messages.h b/source/game/messages.h
index 3b18c33..8efc1bd 100644
--- a/source/game/messages.h
+++ b/source/game/messages.h
@@ -27,6 +27,12 @@ struct PlayerRemoved
 	std::uint16_t id;
 };
 
+struct InternString
+{
+	std::uint16_t id;
+	std::string value;
+};
+
 } // namespace Messages
 } // namespace Msp::Game
 
diff --git a/source/game/networking.cpp b/source/game/networking.cpp
index 49b7d39..30f6b48 100644
--- a/source/game/networking.cpp
+++ b/source/game/networking.cpp
@@ -10,7 +10,9 @@ namespace Msp::Game {
 Networking::Networking(Director &d):
 	event_source(d.get_event_bus()),
 	io_disp(d.get_io_dispatcher())
-{ }
+{
+	strings.emplace_back();
+}
 
 void Networking::start_server(unsigned port)
 {
@@ -44,6 +46,8 @@ void Networking::disable()
 {
 	server_socket.reset();
 	connection.reset();
+	strings.clear();
+	strings.emplace_back();
 	set_state(DISABLED);
 }
 
@@ -74,6 +78,34 @@ void Networking::reap_connections()
 	}
 }
 
+uint16_t Networking::intern_string(const string &value)
+{
+	auto i = find(strings, value);
+	if(i==strings.end())
+	{
+		if(!is_server())
+			throw invalid_state("Networking::intern_string");
+		if(strings.size()>=numeric_limits<uint16_t>::max())
+			throw invalid_state("Networking::intern_string");
+		i = strings.insert(i, value);
+
+		Messages::InternString msg;
+		msg.id = strings.size()-1;
+		msg.value = value;
+		for(const auto &c: clients)
+			c->get_communicator().send(msg);
+	}
+
+	return i-strings.begin();
+}
+
+const string &Networking::get_string(uint16_t id) const
+{
+	if(id>=strings.size())
+		throw key_error(id);
+	return strings[id];
+}
+
 void Networking::add_player(const string &name, function<void(unsigned)> callback)
 {
 	if(state!=CONNECTED && state!=SERVER)
@@ -202,13 +234,33 @@ void Networking::ServerConnection::receive(const Messages::PlayerRemoved &remove
 	}
 }
 
+void Networking::ServerConnection::receive(const Messages::InternString &intern)
+{
+	if(networking.strings.size()<=intern.id)
+		networking.strings.resize(intern.id+1);
+	networking.strings[intern.id] = intern.value;
+}
+
 
 Networking::ClientConnection::ClientConnection(Networking &n, unique_ptr<Net::StreamSocket> s):
 	Connection(n, move(s))
 {
+	communicator.signal_protocol_ready.connect(sigc::mem_fun(this, &ClientConnection::protocol_ready));
 	communicator.add_protocol(networking.protocol, *this);
 }
 
+void Networking::ClientConnection::protocol_ready(const Net::Protocol &p)
+{
+	if(&p==&networking.protocol)
+	{
+		size_t n_strings = networking.strings.size();
+		for(size_t i=1; i<n_strings; ++i)
+			communicator.send(Messages::InternString{ static_cast<uint16_t>(i), networking.strings[i] });
+		if(Stage *stage = networking.director.get_active_stage())
+			communicator.send(Messages::StageActivated{ networking.intern_string(stage->get_name()) });
+	}
+}
+
 void Networking::ClientConnection::receive(const Messages::AddPlayerRequest &add_req)
 {
 	Player &player = networking.create_player(add_req.name);
diff --git a/source/game/networking.h b/source/game/networking.h
index eacba93..b0ee366 100644
--- a/source/game/networking.h
+++ b/source/game/networking.h
@@ -51,7 +51,8 @@ private:
 	class ServerConnection: public Connection,
 		public Net::PacketReceiver<Messages::AddPlayerResponse>,
 		public Net::PacketReceiver<Messages::PlayerAdded>,
-		public Net::PacketReceiver<Messages::PlayerRemoved>
+		public Net::PacketReceiver<Messages::PlayerRemoved>,
+		public Net::PacketReceiver<Messages::InternString>
 	{
 	public:
 		ServerConnection(Networking &, const Net::SockAddr &);
@@ -63,6 +64,7 @@ private:
 		void receive(const Messages::AddPlayerResponse &) override;
 		void receive(const Messages::PlayerAdded &) override;
 		void receive(const Messages::PlayerRemoved &) override;
+		void receive(const Messages::InternString &) override;
 	};
 
 	class ClientConnection: public Connection,
@@ -71,6 +73,7 @@ private:
 	public:
 		ClientConnection(Networking &, std::unique_ptr<Net::StreamSocket>);
 
+		void protocol_ready(const Net::Protocol &);
 		void receive(const Messages::AddPlayerRequest &) override;
 	};
 
@@ -93,15 +96,20 @@ private:
 	std::vector<std::unique_ptr<ClientConnection>> clients;
 	std::vector<Player> players;
 	unsigned next_id = 1;
+	std::vector<std::string> strings;
 
 public:
 	Networking(Director &);
 
 	void start_server(unsigned);
 	void connect_to_server(const std::string &);
+	bool is_server() const { return state==DISABLED || state==SERVER; }
 	void disable();
 	void reap_connections();
 
+	std::uint16_t intern_string(const std::string &);
+	const std::string &get_string(std::uint16_t) const;
+
 	void add_player(const std::string &, std::function<void(unsigned)>);
 private:
 	Player &create_player(const std::string &, unsigned = 0);
diff --git a/source/game/protocol.cpp b/source/game/protocol.cpp
index 1226521..ec34531 100644
--- a/source/game/protocol.cpp
+++ b/source/game/protocol.cpp
@@ -10,6 +10,7 @@ Protocol::Protocol()
 	add<AddPlayerRequest>(&AddPlayerRequest::token, &AddPlayerRequest::name);
 	add<AddPlayerResponse>(&AddPlayerResponse::token, &AddPlayerResponse::id);
 	add<PlayerAdded>(&PlayerAdded::id, &PlayerAdded::name);
+	add<InternString>(&InternString::id, &InternString::value);
 }
 
 } // namespace Msp::Game
-- 
2.45.2