From 54ba50bfb469b93081ea5344e7220a0e10e956c3 Mon Sep 17 00:00:00 2001
From: Xpl0itR <xpl0itr@outlook.com>
Date: Sat, 8 Jun 2024 21:21:08 +0100
Subject: [PATCH] testing

---
 src/LibProtodec/CilReader.cs       | 67 ++++++++++++++++++++++++++++++
 src/LibProtodec/LibProtodec.csproj |  2 +-
 src/LibProtodec/ProtodecContext.cs | 37 +++++++++++++++++
 3 files changed, 105 insertions(+), 1 deletion(-)
 create mode 100644 src/LibProtodec/CilReader.cs

diff --git a/src/LibProtodec/CilReader.cs b/src/LibProtodec/CilReader.cs
new file mode 100644
index 0000000..4c8b8ae
--- /dev/null
+++ b/src/LibProtodec/CilReader.cs
@@ -0,0 +1,67 @@
+// Copyright © 2024 Xpl0itR
+// 
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Reflection.Emit;
+using System.Runtime.CompilerServices;
+using SystemEx.Memory;
+
+namespace LibProtodec;
+
+public static class CilReader
+{
+    // Temporary AOT incompatible method to fill the dictionary, TODO: replace with a source generator
+    private static readonly Dictionary<int, OpCode> OpCodeLookup =
+        typeof(OpCodes).GetFields(BindingFlags.Public | BindingFlags.Static)
+                       .Select(field => (OpCode)field.GetValue(null)!)
+                       .ToDictionary(opCode => (int)(ushort)opCode.Value);
+
+    public static OpCode ReadCilOpCode(this ref MemoryReader reader, out int operandLength)
+    {
+        byte opCodeByte = reader.ReadByte();
+        int opCodeInt = opCodeByte == OpCodes.Prefix1.Value
+            ? (opCodeByte << 8) | reader.ReadByte()
+            : opCodeByte;
+
+        OpCode opCode = OpCodeLookup[opCodeInt];
+        operandLength = SizeOf(opCode.OperandType);
+
+        return opCode;
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static int SizeOf(OperandType operandType)
+    {
+        switch (operandType)
+        {
+            case OperandType.ShortInlineBrTarget:
+            case OperandType.ShortInlineI:
+            case OperandType.ShortInlineVar:
+                return 1;
+            case OperandType.InlineVar:
+                return 2;
+            case OperandType.InlineBrTarget:
+            case OperandType.InlineField:
+            case OperandType.InlineI:
+            case OperandType.InlineMethod:
+            case OperandType.InlineSig:
+            case OperandType.InlineString:
+            case OperandType.InlineSwitch:
+            case OperandType.InlineTok:
+            case OperandType.InlineType:
+            case OperandType.ShortInlineR:
+                return 4;
+            case OperandType.InlineI8:
+            case OperandType.InlineR:
+                return 8;
+            case OperandType.InlineNone:
+            default:
+                return 0;
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/LibProtodec/LibProtodec.csproj b/src/LibProtodec/LibProtodec.csproj
index 8120bb0..de05a5a 100644
--- a/src/LibProtodec/LibProtodec.csproj
+++ b/src/LibProtodec/LibProtodec.csproj
@@ -20,7 +20,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All" />
     <PackageReference Include="System.Reflection.MetadataLoadContext" Version="8.0.0" />
-    <PackageReference Include="Xpl0itR.SystemEx" Version="1.1.0" />
+    <PackageReference Include="Xpl0itR.SystemEx" Version="1.2.0" />
   </ItemGroup>
 
 </Project>
\ No newline at end of file
diff --git a/src/LibProtodec/ProtodecContext.cs b/src/LibProtodec/ProtodecContext.cs
index 23c83f0..b82f93a 100644
--- a/src/LibProtodec/ProtodecContext.cs
+++ b/src/LibProtodec/ProtodecContext.cs
@@ -11,12 +11,14 @@ using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Reflection;
+using System.Reflection.Emit;
 using SystemEx;
 using CommunityToolkit.Diagnostics;
 using LibProtodec.Models;
 using LibProtodec.Models.Fields;
 using LibProtodec.Models.TopLevels;
 using LibProtodec.Models.Types;
+using SystemEx.Memory;
 
 namespace LibProtodec;
 
@@ -70,6 +72,8 @@ public sealed class ProtodecContext
 
         Protobuf protobuf = GetProtobuf(messageClass, message, options);
 
+        ParseWriteToMethodTesting(messageClass);
+
         FieldInfo[]    idFields   = messageClass.GetFields(PublicStatic);
         PropertyInfo[] properties = messageClass.GetProperties(PublicInstanceDeclared);
 
@@ -128,6 +132,39 @@ public sealed class ProtodecContext
         return message;
     }
 
+    private static void ParseWriteToMethodTesting(Type messageClass)
+    {
+        MethodInfo   writeTo = messageClass.GetMethod("WriteTo", BindingFlags.Public | BindingFlags.Instance)!;
+        MemoryReader reader  = new(writeTo.GetMethodBody()!.GetILAsByteArray()!);
+
+        int fieldToken = 0;
+        while (reader.Remaining > 0)
+        {
+            OpCode opCode = reader.ReadCilOpCode(out int operandLength);
+            if (opCode == OpCodes.Ret) // DummyDLL from il2cppdumper will only have ret in method body
+                return;
+
+            if (opCode == OpCodes.Ldfld)
+            {
+                fieldToken = reader.ReadInt32LittleEndian();
+            }
+            else if (opCode == OpCodes.Call)
+            {
+                Guard.IsNotEqualTo(fieldToken, 0);
+                int methodToken = reader.ReadInt32LittleEndian();
+
+                MethodBase? method = messageClass.Module.ResolveMethod(methodToken); // System.NotSupportedException: 'Resolving tokens is not supported on assemblies loaded by a MetadataLoadContext.'
+                FieldInfo?  field  = messageClass.Module.ResolveField(fieldToken);
+
+                //TODO
+            }
+            else
+            {
+                reader.Position += operandLength;
+            }
+        }
+    }
+
     public Enum ParseEnum(Type enumEnum, ParserOptions options = ParserOptions.None)
     {
         Guard.IsTrue(enumEnum.IsEnum);