increase C# custom Python object size to match that of exception to avoid type checks

Author: lostmsu

src/runtime/interop.cs

@@ -67,11 +67,9 @@ public ModulePropertyAttribute()
         }
     }
 
-
-    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
-    internal class ObjectOffset
+    internal static class OriginalObjectOffsets
     {
-        static ObjectOffset()
+        static OriginalObjectOffsets()
         {
             int size = IntPtr.Size;
             var n = 0; // Py_TRACE_REFS add two pointers to PyObject_HEAD
@@ -82,39 +80,52 @@ static ObjectOffset()
 #endif
             ob_refcnt = (n + 0) * size;
             ob_type = (n + 1) * size;
-            ob_dict = (n + 2) * size;
-            ob_data = (n + 3) * size;
+        }
+
+        public static int Size() {
+#if PYTHON_WITH_PYDEBUG
+            return 4 * IntPtr.Size;
+#else
+            return 2 * IntPtr.Size;
+#endif
+        }
+
+#if PYTHON_WITH_PYDEBUG
+        public static int _ob_next;
+        public static int _ob_prev;
+#endif
+        public static int ob_refcnt;
+        public static int ob_type;
+    }
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
+    internal class ObjectOffset
+    {
+        static ObjectOffset()
+        {
+#if PYTHON_WITH_PYDEBUG
+            _ob_next = OriginalObjectOffsets._ob_next;
+            _ob_prev = OriginalObjectOffsets._ob_prev;
+#endif
+            ob_refcnt = OriginalObjectOffsets.ob_refcnt;
+            ob_type = OriginalObjectOffsets.ob_type;
+            ob_dict = ExceptionOffset.ob_dict;
+            ob_data = ExceptionOffset.ob_data;
         }
 
         public static int magic(IntPtr ob)
         {
-            if (IsException(ob))
-            {
-                return ExceptionOffset.ob_data;
-            }
             return ob_data;
         }
 
         public static int DictOffset(IntPtr ob)
         {
-            if (IsException(ob))
-            {
-                return ExceptionOffset.ob_dict;
-            }
             return ob_dict;
         }
 
         public static int Size(IntPtr ob)
         {
-            if (IsException(ob))
-            {
-                return ExceptionOffset.Size();
-            }
-#if PYTHON_WITH_PYDEBUG
-            return 6 * IntPtr.Size;
-#else
-            return 4 * IntPtr.Size;
-#endif
+            return ExceptionOffset.Size();
         }
 
 #if PYTHON_WITH_PYDEBUG
@@ -125,14 +136,6 @@ public static int Size(IntPtr ob)
         public static int ob_type;
         private static int ob_dict;
         private static int ob_data;
-
-        private static bool IsException(IntPtr pyObject)
-        {
-            var type = Runtime.PyObject_TYPE(pyObject);
-            return Runtime.PyObjectType_TypeCheck(type, Exceptions.BaseException)
-                || Runtime.PyObjectType_TypeCheck(type, Runtime.PyTypeType)
-                && Runtime.PyType_IsSubtype(pyObject, Exceptions.BaseException);
-        }
     }
 
     [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
@@ -141,19 +144,17 @@ internal class ExceptionOffset
         static ExceptionOffset()
         {
             Type type = typeof(ExceptionOffset);
-            FieldInfo[] fi = type.GetFields();
-            int size = IntPtr.Size;
+            FieldInfo[] fi = type.GetFields(BindingFlags.Static | BindingFlags.Public);
             for (int i = 0; i < fi.Length; i++)
             {
-                fi[i].SetValue(null, (i * size) + ObjectOffset.ob_type + size);
+                fi[i].SetValue(null, (i * IntPtr.Size) + OriginalObjectOffsets.Size());
             }
-        }
 
-        public static int Size()
-        {
-            return ob_data + IntPtr.Size;
+            size = ob_data + IntPtr.Size;
         }
 
+        public static int Size() { return size; }
+
         // PyException_HEAD
         // (start after PyObject_HEAD)
         public static int dict = 0;
@@ -170,6 +171,8 @@ public static int Size()
         // extra c# data
         public static int ob_dict;
         public static int ob_data;
+
+        static readonly int size;
     }