From 38840fa7c32c0d922aab5bc879c0e7b54424495c Mon Sep 17 00:00:00 2001
From: Nico de Poel <ndepoel@gmail.com>
Date: Mon, 29 Mar 2021 11:00:24 +0200
Subject: [PATCH] Reorganized callbacks so that the function pointers and the
 containing class are all pinned, which makes them safe to store inside the
 DLL and reuse them on subsequent update calls.

---
 Assets/Scripts/Uniquake.cs | 61 ++++++++++++++++++++++++++++++++------
 1 file changed, 52 insertions(+), 9 deletions(-)

diff --git a/Assets/Scripts/Uniquake.cs b/Assets/Scripts/Uniquake.cs
index 859e319..7c65509 100644
--- a/Assets/Scripts/Uniquake.cs
+++ b/Assets/Scripts/Uniquake.cs
@@ -11,8 +11,8 @@ public class Uniquake: MonoBehaviour
     private const int MemSize = 0x4000000;  // 64 MB of heap space
     private const int MaxArgs = 50;     // Corresponds with MAX_NUM_ARGVS in engine
 
-    private UnityCallbacks callbacks = new UnityCallbacks();
     private QuakeParms quakeParms;
+    private UnityCallbacks callbacks = new UnityCallbacks();
 
     void Start()
     {
@@ -32,7 +32,7 @@ public class Uniquake: MonoBehaviour
         
         quakeParms = new QuakeParms
         {
-            baseDir = Application.dataPath,
+            baseDir = Application.persistentDataPath,
             cacheDir = null,
             argc = arguments.Length,
             argv = argv,
@@ -40,7 +40,7 @@ public class Uniquake: MonoBehaviour
             memSize = MemSize,
         };
         
-        Uniquake_Init(callbacks, quakeParms);
+        Uniquake_Init(callbacks.CallbacksPtr, quakeParms);
     }
 
     void Update()
@@ -50,6 +50,8 @@ public class Uniquake: MonoBehaviour
 
     private void OnDestroy()
     {
+        callbacks.Destroy();
+
         if (quakeParms != null)
         {
             if (quakeParms.memBase != IntPtr.Zero)
@@ -76,7 +78,7 @@ public class Uniquake: MonoBehaviour
     private static extern void Uniquake_Echo(UnityCallbacks.DebugLogCallback logCallback, [MarshalAs(UnmanagedType.LPStr)] string message);
     
     [DllImport(DllName, CallingConvention = CallingConvention.Cdecl)]
-    private static extern void Uniquake_Init(UnityCallbacks callbacks, QuakeParms parms);
+    private static extern void Uniquake_Init(IntPtr callbacks, QuakeParms parms);
 
     [DllImport(DllName, CallingConvention = CallingConvention.Cdecl)]
     private static extern void Uniquake_Update(float deltaTime);
@@ -107,20 +109,61 @@ public class Uniquake: MonoBehaviour
         return Time.realtimeSinceStartupAsDouble;
     }
 
-    [StructLayout(LayoutKind.Sequential, Pack = 0)]
+    
     private class UnityCallbacks
     {
+        private UnityCallbacksContainer container;
+        private GCHandle containerHandle;
+
+        public UnityCallbacks()
+        {
+            container = new UnityCallbacksContainer();
+
+            CreateCallback<DebugLogCallback>(Callback_DebugLog, out DebugLogHandle, out container.DebugLogPtr);
+            CreateCallback<DebugLogErrorCallback>(Callback_DebugLogError, out DebugLogErrorHandle, out container.DebugLogErrorPtr);
+            CreateCallback<ApplicationQuitCallback>(Callback_ApplicationQuit, out ApplicationQuitHandle, out container.ApplicationQuitPtr);
+            CreateCallback<RealtimeSinceStartupCallback>(Callback_RealtimeSinceStartup, out RealtimeSinceStartupHandle, out container.RealtimeSinceStartupPtr);
+            
+            containerHandle = GCHandle.Alloc(container, GCHandleType.Pinned);
+        }
+
+        public IntPtr CallbacksPtr => containerHandle.AddrOfPinnedObject();
+
+        public void Destroy()
+        {
+            containerHandle.Free();
+            DebugLogHandle.Free();
+            DebugLogErrorHandle.Free();
+            ApplicationQuitHandle.Free();
+            RealtimeSinceStartupHandle.Free();
+        }
+
+        private static void CreateCallback<TDelegate>(TDelegate callback, out GCHandle handle, out IntPtr ptr)
+        {
+            handle = GCHandle.Alloc(callback);
+            ptr = Marshal.GetFunctionPointerForDelegate(callback);
+        }
+        
         public delegate void DebugLogCallback([MarshalAs(UnmanagedType.LPStr)] string message);
-        public DebugLogCallback DebugLog = Callback_DebugLog;
+        private GCHandle DebugLogHandle;
 
         public delegate void DebugLogErrorCallback([MarshalAs(UnmanagedType.LPStr)] string message);
-        public DebugLogErrorCallback DebugLogError = Callback_DebugLogError;
+        private GCHandle DebugLogErrorHandle;
 
         public delegate void ApplicationQuitCallback(int exitCode);
-        public ApplicationQuitCallback ApplicationQuit = Callback_ApplicationQuit;
+        private GCHandle ApplicationQuitHandle;
 
         public delegate double RealtimeSinceStartupCallback();
-        public RealtimeSinceStartupCallback RealtimeSinceStartup = Callback_RealtimeSinceStartup;
+        private GCHandle RealtimeSinceStartupHandle;
+    }
+
+    [StructLayout(LayoutKind.Sequential, Pack = 0)]
+    private class UnityCallbacksContainer
+    {
+        public IntPtr DebugLogPtr;
+        public IntPtr DebugLogErrorPtr;
+        public IntPtr ApplicationQuitPtr;
+        public IntPtr RealtimeSinceStartupPtr;
     }
 
     [StructLayout(LayoutKind.Sequential, Pack = 0)]