From d426dad820d05aac726814a32466b326d7eaa44f Mon Sep 17 00:00:00 2001
From: Robert Xiao <nneonneo@gmail.com>
Date: Tue, 7 Apr 2020 05:05:21 -0700
Subject: [PATCH] Add support for parsing and interpreting VTables

This prepares for a future PR where we add types to the IDA script
output.
---
 Il2CppInspector.Common/IL2CPP/Il2CppBinary.cs |  7 +++++++
 .../IL2CPP/Il2CppInspector.cs                 | 21 +++++++++++++++++++
 Il2CppInspector.Common/Reflection/TypeInfo.cs | 12 +++++++++++
 3 files changed, 40 insertions(+)

diff --git a/Il2CppInspector.Common/IL2CPP/Il2CppBinary.cs b/Il2CppInspector.Common/IL2CPP/Il2CppBinary.cs
index cee808a..b4a1662 100644
--- a/Il2CppInspector.Common/IL2CPP/Il2CppBinary.cs
+++ b/Il2CppInspector.Common/IL2CPP/Il2CppBinary.cs
@@ -53,6 +53,9 @@ namespace Il2CppInspector
         // One invoker specifies a return type and argument list. Multiple methods with the same signature can be invoked with the same invoker
         public ulong[] MethodInvokePointers { get; private set; }
 
+        // Version 16 and below: method references for vtable
+        public uint[] VTableMethodReferences { get; private set; }
+
         // Generic method specs for vtables
         public Il2CppMethodSpec[] MethodSpecs { get; private set; }
 
@@ -245,6 +248,10 @@ namespace Il2CppInspector
             // >=22: unresolvedVirtualCallPointers
             // >=23: interopData
 
+            if (Image.Version < 19) {
+                VTableMethodReferences = image.ReadMappedArray<uint>(MetadataRegistration.methodReferences, (int)MetadataRegistration.methodReferencesCount);
+            }
+
             // Generic type and method specs (open and closed constructed types)
             MethodSpecs = image.ReadMappedArray<Il2CppMethodSpec>(MetadataRegistration.methodSpecs, (int) MetadataRegistration.methodSpecsCount);
 
diff --git a/Il2CppInspector.Common/IL2CPP/Il2CppInspector.cs b/Il2CppInspector.Common/IL2CPP/Il2CppInspector.cs
index 46f23cc..a86b71a 100644
--- a/Il2CppInspector.Common/IL2CPP/Il2CppInspector.cs
+++ b/Il2CppInspector.Common/IL2CPP/Il2CppInspector.cs
@@ -294,6 +294,27 @@ namespace Il2CppInspector
             return Binary.MethodInvokerIndices[module][methodInModule - 1];
         }
 
+        public MetadataUsage[] GetVTable(Il2CppTypeDefinition definition) {
+            MetadataUsage[] res = new MetadataUsage[definition.vtable_count];
+            for (int i = 0; i < definition.vtable_count; i++) {
+                var encodedIndex = VTableMethodIndices[definition.vtableStart + i];
+                uint index;
+                MetadataUsageType usageType;
+                if (Version < 19) {
+                    var flag = encodedIndex & 0x80000000;
+                    index = Binary.VTableMethodReferences[encodedIndex & 0x7FFFFFFF];
+                    usageType = (flag != 0) ? MetadataUsageType.MethodRef : MetadataUsageType.MethodDef;
+                } else {
+                    var encodedType = encodedIndex & 0xE0000000;
+                    usageType = (MetadataUsageType)(encodedType >> 29);
+                    index = encodedIndex & 0x1FFFFFFF;
+                }
+                if (index != 0)
+                    res[i] = new MetadataUsage(usageType, (int)index, i);
+            }
+            return res;
+        }
+
         public static List<Il2CppInspector> LoadFromFile(string codeFile, string metadataFile) {
             // Load the metadata file
             Metadata metadata;
diff --git a/Il2CppInspector.Common/Reflection/TypeInfo.cs b/Il2CppInspector.Common/Reflection/TypeInfo.cs
index dfa5186..79a7628 100644
--- a/Il2CppInspector.Common/Reflection/TypeInfo.cs
+++ b/Il2CppInspector.Common/Reflection/TypeInfo.cs
@@ -133,6 +133,18 @@ namespace Il2CppInspector.Reflection {
         // Get a property by its name
         public PropertyInfo GetProperty(string name) => DeclaredProperties.FirstOrDefault(p => p.Name == name);
 
+        public MethodBase[] GetVTable() {
+            var definition = Definition;
+
+            MetadataUsage[] vt = Assembly.Model.Package.GetVTable(definition);
+            MethodBase[] res = new MethodBase[vt.Length];
+            for (int i = 0; i < vt.Length; i++) {
+                if (vt[i] != null)
+                    res[i] = Assembly.Model.GetMetadataUsageMethod(vt[i]);
+            }
+            return res;
+        }
+
         // Method that the type is declared in if this is a type parameter of a generic method
         // TODO: Make a unit test from this: https://docs.microsoft.com/en-us/dotnet/api/system.type.declaringmethod?view=netframework-4.8
         public MethodBase DeclaringMethod;