From e44432c068eda1789961c49a98f22c9c46929c52 Mon Sep 17 00:00:00 2001
From: Deukhoofd <deukhoofd@gmail.com>
Date: Thu, 12 Sep 2019 16:57:41 +0200
Subject: [PATCH] Handling for caching pointers to userdata objects

---
 PorygonSharp/EvalValues/EvalValueCreator.cs   |  8 ++--
 PorygonSharp/EvalValues/ListEvalValue.cs      |  6 +--
 .../EvalValues/ObjectEvalValueHandler.cs      | 44 +++++++++++++++++++
 PorygonSharp/UserData/UserData.cs             |  6 +--
 4 files changed, 52 insertions(+), 12 deletions(-)
 create mode 100644 PorygonSharp/EvalValues/ObjectEvalValueHandler.cs

diff --git a/PorygonSharp/EvalValues/EvalValueCreator.cs b/PorygonSharp/EvalValues/EvalValueCreator.cs
index 50821f8..41edf71 100644
--- a/PorygonSharp/EvalValues/EvalValueCreator.cs
+++ b/PorygonSharp/EvalValues/EvalValueCreator.cs
@@ -16,8 +16,8 @@ namespace PorygonSharp.EvalValues
             if (type.IsEnum && !type.IsGenericParameter)
             {
                 var typeHash = UserDataHandler.GetTypeId(type);
-                var handle   = GCHandle.Alloc(o, GCHandleType.WeakTrackResurrection);
-                return new EvalValue(CreateUserDataEvalValue(typeHash, GCHandle.ToIntPtr(handle)));
+                var ptr = ObjectEvalValueHandler.GetObjectPtr(o);
+                return new EvalValue(CreateUserDataEvalValue(typeHash, ptr));
             }
             var typeCode = Type.GetTypeCode(type);
             switch (typeCode)
@@ -48,8 +48,8 @@ namespace PorygonSharp.EvalValues
                         throw new Exception($"Type is not registered for use: {type.FullName}");
                     }
                     var typeHash = UserDataHandler.GetTypeId(type);
-                    var handle   = GCHandle.Alloc(o, GCHandleType.WeakTrackResurrection);
-                    return new EvalValue(CreateUserDataEvalValue(typeHash, GCHandle.ToIntPtr(handle)));
+                    var ptr = ObjectEvalValueHandler.GetObjectPtr(o);
+                    return new EvalValue(CreateUserDataEvalValue(typeHash, ptr));
                 default:
                     throw new Exception($"Type {type} is not currently available as EvalValue");
             }
diff --git a/PorygonSharp/EvalValues/ListEvalValue.cs b/PorygonSharp/EvalValues/ListEvalValue.cs
index 419847d..50905f6 100644
--- a/PorygonSharp/EvalValues/ListEvalValue.cs
+++ b/PorygonSharp/EvalValues/ListEvalValue.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Collections;
-using System.Diagnostics;
 using System.Runtime.InteropServices;
 
 namespace PorygonSharp.EvalValues
@@ -21,9 +20,8 @@ namespace PorygonSharp.EvalValues
             var valueType = type.IsArray ? type.GetElementType() : type.GetGenericArguments()[0];
             if (valueType == null)
                 throw new ArgumentNullException();
-            
-            var parentHandle = GCHandle.Alloc(list, GCHandleType.WeakTrackResurrection);
-            ParentCollection = GCHandle.ToIntPtr(parentHandle);
+
+            ParentCollection = ObjectEvalValueHandler.GetObjectPtr(list);
             Getter = Marshal.GetFunctionPointerForDelegate(new GetterDelegate((parent, index) =>
             {
                 var val = new EvalValue(index).EvaluateInteger();
diff --git a/PorygonSharp/EvalValues/ObjectEvalValueHandler.cs b/PorygonSharp/EvalValues/ObjectEvalValueHandler.cs
new file mode 100644
index 0000000..1e5f359
--- /dev/null
+++ b/PorygonSharp/EvalValues/ObjectEvalValueHandler.cs
@@ -0,0 +1,44 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+
+namespace PorygonSharp.EvalValues
+{
+    internal static class ObjectEvalValueHandler
+    {
+        private struct PtrObject
+        {
+            public readonly IntPtr Pointer;
+            public readonly WeakReference<object> WeakReference;
+
+            public PtrObject(IntPtr pointer, WeakReference<object> weakReference)
+            {
+                Pointer = pointer;
+                WeakReference = weakReference;
+            }
+        }
+        
+        private static readonly Dictionary<int, PtrObject> CreatedPointers = new Dictionary<int, PtrObject>();
+
+        public static IntPtr GetObjectPtr(object o)
+        {
+            var hash = o.GetHashCode();
+            if (CreatedPointers.TryGetValue(hash, out var ptrObject))
+            {
+                if (ptrObject.WeakReference.TryGetTarget(out _))
+                {
+                    return ptrObject.Pointer;
+                }
+                else
+                {
+                    CreatedPointers.Remove(hash);
+                }
+            }
+            var handle   = GCHandle.Alloc(o, GCHandleType.WeakTrackResurrection);
+            var ptr = GCHandle.ToIntPtr(handle);
+            ptrObject = new PtrObject(ptr, new WeakReference<object>(o));
+            CreatedPointers.Add(o.GetHashCode(), ptrObject);
+            return ptrObject.Pointer;
+        }
+    }
+}
\ No newline at end of file
diff --git a/PorygonSharp/UserData/UserData.cs b/PorygonSharp/UserData/UserData.cs
index 2b8242b..875753d 100644
--- a/PorygonSharp/UserData/UserData.cs
+++ b/PorygonSharp/UserData/UserData.cs
@@ -160,14 +160,12 @@ namespace PorygonSharp.UserData
             if (_implicitCasts.TryGetValue(expectedType, out var func))
             {
                 var castVal = func.Invoke(null, new[] {obj});
-                var handle = GCHandle.Alloc(castVal, GCHandleType.WeakTrackResurrection);
-                return GCHandle.ToIntPtr(handle);
+                return EvalValueCreator.CreateValue(castVal).GetPointer();
             }
             if (_explicitCasts.TryGetValue(expectedType, out func))
             {
                 var castVal = func.Invoke(null, new[] {obj});
-                var handle = GCHandle.Alloc(castVal, GCHandleType.WeakTrackResurrection);
-                return GCHandle.ToIntPtr(handle);
+                return EvalValueCreator.CreateValue(castVal).GetPointer();
             }
             throw new Exception("Invalid cast kind");
         }