From 84670191689b894bad196d096542468c6a7b3863 Mon Sep 17 00:00:00 2001
From: js6pak <kubastaron@hotmail.com>
Date: Sat, 10 Dec 2022 18:01:58 +0100
Subject: [PATCH] Workaround garbage field offset values

---
 .../Extensions/CustomAttributeEx.cs           | 36 ++++++++++++-------
 .../Passes/Pass11ComputeTypeSpecifics.cs      |  8 +++++
 .../Passes/Pass21GenerateValueTypeFields.cs   |  5 +--
 3 files changed, 32 insertions(+), 17 deletions(-)

diff --git a/Il2CppInterop.Generator/Extensions/CustomAttributeEx.cs b/Il2CppInterop.Generator/Extensions/CustomAttributeEx.cs
index 1f0c5700..57f0ddf3 100644
--- a/Il2CppInterop.Generator/Extensions/CustomAttributeEx.cs
+++ b/Il2CppInterop.Generator/Extensions/CustomAttributeEx.cs
@@ -1,5 +1,3 @@
-using System.Globalization;
-using System.Linq;
 using Mono.Cecil;
 
 namespace Il2CppInterop.Generator.Extensions;
@@ -8,30 +6,42 @@ public static class CustomAttributeEx
 {
     public static long ExtractOffset(this ICustomAttributeProvider originalMethod)
     {
-        return Extract(originalMethod, "AddressAttribute", "Offset");
+        return ExtractLong(originalMethod, "AddressAttribute", "Offset");
     }
 
     public static long ExtractRva(this ICustomAttributeProvider originalMethod)
     {
-        return Extract(originalMethod, "AddressAttribute", "RVA");
+        return ExtractLong(originalMethod, "AddressAttribute", "RVA");
     }
 
     public static long ExtractToken(this ICustomAttributeProvider originalMethod)
     {
-        return Extract(originalMethod, "TokenAttribute", "Token");
+        return ExtractLong(originalMethod, "TokenAttribute", "Token");
     }
 
-    private static long Extract(this ICustomAttributeProvider originalMethod, string attributeName,
+    public static int ExtractFieldOffset(this ICustomAttributeProvider originalField)
+    {
+        return ExtractInt(originalField, "FieldOffsetAttribute", "Offset");
+    }
+
+    private static string Extract(this ICustomAttributeProvider originalMethod, string attributeName,
         string parameterName)
     {
-        var addressAttribute =
-            originalMethod.CustomAttributes.SingleOrDefault(it => it.AttributeType.Name == attributeName);
-        var rvaField = addressAttribute?.Fields.SingleOrDefault(it => it.Name == parameterName);
+        var attribute = originalMethod.CustomAttributes.SingleOrDefault(it => it.AttributeType.Name == attributeName);
+        var field = attribute?.Fields.SingleOrDefault(it => it.Name == parameterName);
 
-        if (rvaField?.Name == null) return 0;
+        if (field?.Name == null) return null;
+
+        return (string)field.Value.Argument.Value;
+    }
 
-        var addressString = (string)rvaField.Value.Argument.Value;
-        long.TryParse(addressString.Substring(2), NumberStyles.HexNumber, null, out var address);
-        return address;
+    private static long ExtractLong(this ICustomAttributeProvider originalMethod, string attributeName, string parameterName)
+    {
+        return Convert.ToInt64(Extract(originalMethod, attributeName, parameterName), 16);
+    }
+
+    private static int ExtractInt(this ICustomAttributeProvider originalMethod, string attributeName, string parameterName)
+    {
+        return Convert.ToInt32(Extract(originalMethod, attributeName, parameterName), 16);
     }
 }
diff --git a/Il2CppInterop.Generator/Passes/Pass11ComputeTypeSpecifics.cs b/Il2CppInterop.Generator/Passes/Pass11ComputeTypeSpecifics.cs
index 3e609c98..43730192 100644
--- a/Il2CppInterop.Generator/Passes/Pass11ComputeTypeSpecifics.cs
+++ b/Il2CppInterop.Generator/Passes/Pass11ComputeTypeSpecifics.cs
@@ -1,4 +1,5 @@
 using Il2CppInterop.Generator.Contexts;
+using Il2CppInterop.Generator.Extensions;
 
 namespace Il2CppInterop.Generator.Passes;
 
@@ -18,6 +19,13 @@ private static void ComputeSpecifics(TypeRewriteContext typeContext)
 
         foreach (var originalField in typeContext.OriginalType.Fields)
         {
+            // Sometimes il2cpp metadata has invalid field offsets for some reason (https://github.com/SamboyCoding/Cpp2IL/issues/167)
+            if (originalField.ExtractFieldOffset() >= 0x8000000)
+            {
+                typeContext.ComputedTypeSpecifics = TypeRewriteContext.TypeSpecifics.NonBlittableStruct;
+                return;
+            }
+
             if (originalField.IsStatic) continue;
 
             var fieldType = originalField.FieldType;
diff --git a/Il2CppInterop.Generator/Passes/Pass21GenerateValueTypeFields.cs b/Il2CppInterop.Generator/Passes/Pass21GenerateValueTypeFields.cs
index 4deb5178..c7e0d6c5 100644
--- a/Il2CppInterop.Generator/Passes/Pass21GenerateValueTypeFields.cs
+++ b/Il2CppInterop.Generator/Passes/Pass21GenerateValueTypeFields.cs
@@ -42,10 +42,7 @@ public static void DoPass(RewriteGlobalContext context)
                                 ? assemblyContext.Imports.Module.IntPtr()
                                 : assemblyContext.RewriteTypeRef(field.FieldType));
 
-                        newField.Offset = Convert.ToInt32(
-                            (string)field.CustomAttributes
-                                .Single(it => it.AttributeType.Name == "FieldOffsetAttribute")
-                                .Fields.Single().Argument.Value, 16);
+                        newField.Offset = field.ExtractFieldOffset();
 
                         // Special case: bools in Il2Cpp are bytes
                         if (newField.FieldType.FullName == "System.Boolean")