feat: Supporting managed types in NetworkVariable [MTT-4594] (#2219)

* feat: Supporting managed types in NetworkVariable.

Also changes NetworkVariable to deserialize INetworkSerializable types in-place - this is done to avoid having a GC alloc every time the value changes. There will only be a GC alloc if it receives an updated value and the current value is null.

Managed types are supported in two ways:

1. By making them INetworkSerializable, or
2. By assigning the delegates UserNetworkVariableSerialization<T>.WriteValue and UserNetworkVariableSerialization<T>.ReadValue

If a managed type is passed in without meeting one of those criteria (or any unsupported type), then an exception will be thrown the first time the NetworkVariable is read or written. That timing is to ensure no weird behavior with exceptions being thrown before user code is able to assign the delegates.

Co-authored-by: Fatih Mar <mfatihmar@gmail.com>

Author: ShadauxCat

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -23,6 +23,8 @@ Additional documentation and release notes are available at [Multiplayer Documen
 - The send queues of `UnityTransport` are now dynamically-sized. This means that there shouldn't be any need anymore to tweak the 'Max Send Queue Size' value. In fact, this field is now removed from the inspector and will not be serialized anymore. It is still possible to set it manually using the `MaxSendQueueSize` property, but it is not recommended to do so aside from some specific needs (e.g. limiting the amount of memory used by the send queues in very constrained environments). (#2212)
 - As a consequence of the above change, the `UnityTransport.InitialMaxSendQueueSize` field is now deprecated. There is no default value anymore since send queues are dynamically-sized. (#2212)
 - The debug simulator in `UnityTransport` is now non-deterministic. Its random number generator used to be seeded with a constant value, leading to the same pattern of packet drops, delays, and jitter in every run. (#2196)
+- `NetworkVariable<>` now supports managed `INetworkSerializable` types, as well as other managed types with serialization/deserialization delegates registered to `UserNetworkVariableSerialization<T>.WriteValue` and `UserNetworkVariableSerialization<T>.ReadValue` (#2219)
+- `NetworkVariable<>` and `BufferSerializer<BufferSerializerReader>` now deserialize `INetworkSerializable` types in-place, rather than constructing new ones. (#2219)
 
 ### Fixed
 

com.unity.netcode.gameobjects/Editor/CodeGen/CodeGenHelpers.cs

@@ -123,6 +123,19 @@ public static bool HasInterface(this TypeReference typeReference, string interfa
             try
             {
                 var typeDef = typeReference.Resolve();
+                // Note: this won't catch generics correctly.
+                //
+                //     class Foo<T>: IInterface<T> {}
+                //     class Bar: Foo<int> {}
+                //
+                // Bar.HasInterface(IInterface<int>) -> returns false even though it should be true.
+                //
+                // This can be fixed (see GetAllFieldsAndResolveGenerics() in NetworkBehaviourILPP to understand how)
+                // but right now we don't need that to work so it's left alone to reduce complexity
+                if (typeDef.BaseType.HasInterface(interfaceTypeFullName))
+                {
+                    return true;
+                }
                 var typeFaces = typeDef.Interfaces;
                 return typeFaces.Any(iface => iface.InterfaceType.FullName == interfaceTypeFullName);
             }

com.unity.netcode.gameobjects/Editor/CodeGen/NetworkBehaviourILPP.cs

@@ -151,7 +151,8 @@ public override void ReadField(FastBufferReader reader)
             reader.ReadValueSafe(out ushort count);
             for (int i = 0; i < count; i++)
             {
-                NetworkVariableSerialization<T>.Read(reader, out T value);
+                var value = new T();
+                NetworkVariableSerialization<T>.Read(reader, ref value);
                 m_List.Add(value);
             }
         }
@@ -167,7 +168,8 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
                 {
                     case NetworkListEvent<T>.EventType.Add:
                         {
-                            NetworkVariableSerialization<T>.Read(reader, out T value);
+                            var value = new T();
+                            NetworkVariableSerialization<T>.Read(reader, ref value);
                             m_List.Add(value);
 
                             if (OnListChanged != null)
@@ -195,7 +197,8 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
                     case NetworkListEvent<T>.EventType.Insert:
                         {
                             reader.ReadValueSafe(out int index);
-                            NetworkVariableSerialization<T>.Read(reader, out T value);
+                            var value = new T();
+                            NetworkVariableSerialization<T>.Read(reader, ref value);
 
                             if (index < m_List.Length)
                             {
@@ -231,7 +234,8 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
                         break;
                     case NetworkListEvent<T>.EventType.Remove:
                         {
-                            NetworkVariableSerialization<T>.Read(reader, out T value);
+                            var value = new T();
+                            NetworkVariableSerialization<T>.Read(reader, ref value);
                             int index = m_List.IndexOf(value);
                             if (index == -1)
                             {
@@ -293,7 +297,8 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
                     case NetworkListEvent<T>.EventType.Value:
                         {
                             reader.ReadValueSafe(out int index);
-                            NetworkVariableSerialization<T>.Read(reader, out T value);
+                            var value = new T();
+                            NetworkVariableSerialization<T>.Read(reader, ref value);
                             if (index >= m_List.Length)
                             {
                                 throw new Exception("Shouldn't be here, index is higher than list length");

com.unity.netcode.gameobjects/Runtime/NetworkVariable/Collections/NetworkList.cs

@@ -1,7 +1,5 @@
 using UnityEngine;
 using System;
-using System.Runtime.CompilerServices;
-using Unity.Collections.LowLevel.Unsafe;
 
 namespace Unity.Netcode
 {
@@ -10,7 +8,7 @@ namespace Unity.Netcode
     /// </summary>
     /// <typeparam name="T">the unmanaged type for <see cref="NetworkVariable{T}"/> </typeparam>
     [Serializable]
-    public class NetworkVariable<T> : NetworkVariableBase where T : unmanaged
+    public class NetworkVariable<T> : NetworkVariableBase
     {
         /// <summary>
         /// Delegate type for value changed event
@@ -52,7 +50,7 @@ public virtual T Value
             set
             {
                 // Compare bitwise
-                if (ValueEquals(ref m_InternalValue, ref value))
+                if (NetworkVariableSerialization<T>.AreEqual(ref m_InternalValue, ref value))
                 {
                     return;
                 }
@@ -66,20 +64,6 @@ public virtual T Value
             }
         }
 
-        // Compares two values of the same unmanaged type by underlying memory
-        // Ignoring any overridden value checks
-        // Size is fixed
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static unsafe bool ValueEquals(ref T a, ref T b)
-        {
-            // get unmanaged pointers
-            var aptr = UnsafeUtility.AddressOf(ref a);
-            var bptr = UnsafeUtility.AddressOf(ref b);
-
-            // compare addresses
-            return UnsafeUtility.MemCmp(aptr, bptr, sizeof(T)) == 0;
-        }
-
         /// <summary>
         /// Sets the <see cref="Value"/>, marks the <see cref="NetworkVariable{T}"/> dirty, and invokes the <see cref="OnValueChanged"/> callback
         /// if there are subscribers to that event.
@@ -115,7 +99,7 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
             // would be stored in different fields
 
             T previousValue = m_InternalValue;
-            NetworkVariableSerialization<T>.Read(reader, out m_InternalValue);
+            NetworkVariableSerialization<T>.Read(reader, ref m_InternalValue);
 
             if (keepDirtyDelta)
             {
@@ -128,7 +112,7 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
         /// <inheritdoc />
         public override void ReadField(FastBufferReader reader)
         {
-            NetworkVariableSerialization<T>.Read(reader, out m_InternalValue);
+            NetworkVariableSerialization<T>.Read(reader, ref m_InternalValue);
         }
 
         /// <inheritdoc />