Turning very complicated arithmetic and reverse engineered check into useable code in C#

Question

so I have this problem of me not understanding how to convert this one function into useable code in C#. Problem being that I am currently hooking into a game via C# and I want to rebuild a function that is very much required on the C# side of my modification, the game is of course written in C++

void __fastcall CachedReader::OutOfBoundsError(CachedReader *this, unsigned __int64 a2, __int64 a3)
{
    ulong totalSize = a2 + a3;
    if ( totalSize > (*(__int64 (__fastcall **)(_QWORD))(**((_QWORD **)this + 3) + 48i64))(*((_QWORD *)this + 3)) )
    {
        //TODO: Error logging here
    }
}

Any help converting this is greatly appreciated :)

Answer 1

This is a quick follow-up for anyone running into the same problem. I managed to figure it out with a bit of brain power

delegate long GetFileLengthDelegate(ulong v2);
        internal long GetFileLength()
        {
            IntPtr functionPointer = new IntPtr((long)*((ulong*)(**((ulong**)readerPtr + 3) + 48)));
            GetFileLengthDelegate getFileLength = Marshal.GetDelegateForFunctionPointer<GetFileLengthDelegate>(functionPointer);

            return getFileLength((*((ulong*)readerPtr + 3)));
        }

Apparently those types of statements are function pointers and the the second set of parantheses act as the parameters for it. Hope it can help anyone out there!