#1 - quicr module

modules/serialization/include/tw/serial/WorldStateWriter.hpp

@@ -9,8 +9,9 @@
  * Wire format (all values little-endian):
  *
  *   ┌──────────────────────────────────────────────────────────┐
- *   │ Header (12 bytes)                                        │
- *   │   packet_type  : uint32   (PacketType::WORLD_STATE = 3)  │
+ *   │ Header (16 bytes)                                        │
+ *   │   message_type : uint32   (supplied by the caller)       │
+ *   │   sequence     : uint32   (always 0, no reply expected)  │
  *   │   frame_idx    : uint32                                  │
  *   │   entity_count : uint32   (number of position records)   │
  *   ├──────────────────────────────────────────────────────────┤
@@ -66,12 +67,6 @@
 
 namespace tw::serial {
 
-// ── Packet type tag ───────────────────────────────────────────────────────
-// Mirrors PacketType::WORLD_STATE_PACKET (value 3) in packets/Packet.hpp.
-// Hardcoded here so the serialisation module does not depend on the network
-// module — the numerical value must stay in sync if the enum changes.
-inline constexpr uint32_t kWorldStatePacketType = 3; // WORLD_STATE_PACKET
-
 // ──────────────────────────────────────────────────────────────────────────
 // WorldStateWriter
 // ──────────────────────────────────────────────────────────────────────────
@@ -87,14 +82,20 @@ public:
     explicit WorldStateWriter(BinaryBuffer& buf) noexcept : m_w(buf) {}
 
     /**
-     * Write the packet header.  Call once per frame, before everything else.
+     * Write the header.  Call once per frame, before everything else.
      * entity_count is patched in end().
+     *
+     * message_type is supplied by the caller so that this module stays free of
+     * the address the message is delivered to.
      */
-    void begin(uint32_t frame_idx) noexcept {
+    void begin(uint32_t frame_idx, uint32_t message_type) noexcept {
         m_entity_count = 0;
 
-        // packet_type — lets the receiver dispatch without peeking further
-        m_w.encode<uint32_t>(kWorldStatePacketType);
+        // message_type — lets the receiver dispatch without peeking further
+        m_w.encode<uint32_t>(message_type);
+
+        // sequence — this message is never a reply to a request
+        m_w.encode<uint32_t>(0);
 
         // frame_idx
         m_w.encode<uint32_t>(frame_idx);