Cpp2IL/LibCpp2IL/MetadataUsage.cs

using System;
using LibCpp2IL.BinaryStructures;
using LibCpp2IL.Metadata;
using LibCpp2IL.Reflection;

namespace LibCpp2IL
{
    public class MetadataUsage
    {
        public readonly MetadataUsageType Type;
        public readonly ulong Offset;
        private readonly uint _value;

        private string? _cachedName;

        private Il2CppType? _cachedType;
        private Il2CppTypeReflectionData? _cachedTypeReflectionData;

        private Il2CppMethodDefinition? _cachedMethod;

        private Il2CppFieldDefinition? _cachedField;

        private string? _cachedLiteral;

        private Cpp2IlMethodRef? _cachedGenericMethod;

        public MetadataUsage(MetadataUsageType type, ulong offset, uint value)
        {
            Type = type;
            _value = value;
            Offset = offset;
        }

        public uint RawValue => _value;

        public object Value
        {
            get
            {
                switch (Type)
                {
                    case MetadataUsageType.Type:
                    case MetadataUsageType.TypeInfo:
                        return AsType();
                    case MetadataUsageType.MethodDef:
                        return AsMethod();
                    case MetadataUsageType.FieldInfo:
                        return AsField();
                    case MetadataUsageType.StringLiteral:
                        return AsLiteral();
                    case MetadataUsageType.MethodRef:
                        return AsGenericMethodRef();
                    default:
                        throw new ArgumentOutOfRangeException();
                }
            }
        }

        public Il2CppTypeReflectionData AsType()
        {
            if (_cachedTypeReflectionData == null)
            {
                switch (Type)
                {
                    case MetadataUsageType.Type:
                    case MetadataUsageType.TypeInfo:
                        try
                        {
                            _cachedType = LibCpp2IlMain.Binary!.GetType((int) _value);
                            _cachedTypeReflectionData = LibCpp2ILUtils.GetTypeReflectionData(_cachedType)!;
                            _cachedName = LibCpp2ILUtils.GetTypeReflectionData(_cachedType)?.ToString();
                        }
                        catch (Exception e)
                        {
                            throw new Exception($"Failed to convert this metadata usage to a type, but it is of type {Type}, with a value of {_value} (0x{_value:X}). There are {LibCpp2IlMain.Binary!.NumTypes} types", e);
                        }

                        break;
                    default:
                        throw new Exception($"Cannot cast metadata usage of kind {Type} to a Type");
                }
            }

            return _cachedTypeReflectionData!;
        }

        public Il2CppMethodDefinition AsMethod()
        {
            if (_cachedMethod == null)
            {
                switch (Type)
                {
                    case MetadataUsageType.MethodDef:
                        _cachedMethod = LibCpp2IlMain.TheMetadata!.methodDefs[_value];
                        _cachedName = _cachedMethod.GlobalKey;
                        break;
                    default:
                        throw new Exception($"Cannot cast metadata usage of kind {Type} to a Method Def");
                }
            }

            return _cachedMethod!;
        }

        public Il2CppFieldDefinition AsField()
        {
            if (_cachedField == null)
            {
                switch (Type)
                {
                    case MetadataUsageType.FieldInfo:
                        var fieldRef = LibCpp2IlMain.TheMetadata!.fieldRefs[_value];
                        _cachedField = fieldRef.FieldDefinition;
                        _cachedName = fieldRef.DeclaringTypeDefinition!.FullName + "." + _cachedField!.Name;
                        break;
                    default:
                        throw new Exception($"Cannot cast metadata usage of kind {Type} to a Field");
                }
            }

            return _cachedField;
        }

        public string AsLiteral()
        {
            if (_cachedLiteral == null)
            {
                switch (Type)
                {
                    case MetadataUsageType.StringLiteral:
                        _cachedName = _cachedLiteral = LibCpp2IlMain.TheMetadata!.GetStringLiteralFromIndex(_value);
                        break;
                    default:
                        throw new Exception($"Cannot cast metadata usage of kind {Type} to a String Literal");
                }
            }

            return _cachedLiteral;
        }

        public Cpp2IlMethodRef AsGenericMethodRef()
        {
            if (_cachedGenericMethod == null)
            {
                switch (Type)
                {
                    case MetadataUsageType.MethodRef: 
                        var methodSpec = LibCpp2IlMain.Binary!.GetMethodSpec((int) _value);

                        _cachedGenericMethod = new Cpp2IlMethodRef(methodSpec);
                        _cachedName = _cachedGenericMethod.ToString();
                        break;
                    default:
                        throw new Exception($"Cannot cast metadata usage of kind {Type} to a Generic Method Ref");
                }
            }
            return _cachedGenericMethod;
        }

        public override string ToString()
        {
            return $"Metadata Usage {{type={Type}, Value={Value}}}";
        }

        public bool IsValid
        {
            get
            {
                try
                {
                    var _ = Value;
                    return true;
                }
                catch (Exception)
                {
                    return false;
                }
            }
        }
        

        public static MetadataUsage? DecodeMetadataUsage(ulong encoded, ulong address)
        {
            var encodedType = encoded & 0xE000_0000;
            var type = (MetadataUsageType) (encodedType >> 29);
            if (type <= MetadataUsageType.MethodRef && type >= MetadataUsageType.TypeInfo)
            {
                var index = (uint) (encoded & 0x1FFF_FFFF);
                
                if (LibCpp2IlMain.MetadataVersion >= 27)
                    index >>= 1;

                if (type is MetadataUsageType.Type or MetadataUsageType.TypeInfo && index > LibCpp2IlMain.Binary!.NumTypes)
                    return null;

                if (type == MetadataUsageType.MethodDef && index > LibCpp2IlMain.TheMetadata!.methodDefs.Length)
                    return null;


                return new MetadataUsage(type, address, index);
            }

            return null;
        }
    }
}