Need help with function

[Marton]

...To all, but specially to de4dot's author.
I'm seeking for help with this function:

[return: MarshalAs(UnmanagedType.U1)]
public virtual unsafe bool IsSerialValid(SerialNumber serialNumber)
{
    byte num4;
    cSerialNumber number;
    int num2 = (int) stackalloc byte[__CxxQueryExceptionSize()];
    SerialToImpl(&number, serialNumber);
    byte num3 = 0;
    try
    {
        uint num;
        try
        {
            bool flag = ActivatorLib.cSerialNumber.IsValid((cSerialNumber modopt(IsConst)* modopt(IsConst) modopt(IsConst)) &number);
            num3 = 1;
            ActivatorLib.cSerialNumber.{dtor}(&number);
            num4 = (byte) flag;
            goto Label_01FC;
        }
        catch when (?)
        {
            num = 0;
            __CxxRegisterExceptionObject((void*) Marshal.GetExceptionPointers(), (void*) num2);
            try
            {
                try
                {
                    bad_activator modopt(IsConst)* modopt(IsImplicitlyDereferenced) _activatorPtr;
                    throw new ActivatorException(new string(*_activatorPtr[0][4](_activatorPtr)));
                }
                catch when (?)
                {
                }
                if (num != 0)
                {
                    throw;
                }
            }
            finally
            {
                __CxxUnregisterExceptionObject((void*) num2, (int) num);
            }
        }
        catch when (?)
        {
            num = 0;
            __CxxRegisterExceptionObject((void*) Marshal.GetExceptionPointers(), (void*) num2);
            try
            {
                try
                {
                    throw new ActivatorException("Out of memory");
                }
                catch when (?)
                {
                }
                if (num != 0)
                {
                    throw;
                }
            }
            finally
            {
                __CxxUnregisterExceptionObject((void*) num2, (int) num);
            }
        }
        catch when (?)
        {
            num = 0;
            __CxxRegisterExceptionObject((void*) Marshal.GetExceptionPointers(), (void*) num2);
            try
            {
                try
                {
                    basic_string<char,std::char_traits<char>,std::allocator<char> > local;
                    std.basic_string<char,std::char_traits<char>,std::allocator<char> >.{ctor}(&local, &??_C@_0BF@JJANBHDP@Standard?5exception?3?5?$AA@);
                    try
                    {
                        exception modopt(IsConst)* modopt(IsImplicitlyDereferenced) exceptionPtr;
                        std.basic_string<char,std::char_traits<char>,std::allocator<char> >.+=(&local, *exceptionPtr[0][4](exceptionPtr));
                        throw new ActivatorException(new string(std.basic_string<char,std::char_traits<char>,std::allocator<char> >.c_str((basic_string<char,std::char_traits<char>,std::allocator<char> > modopt(IsConst)* modopt(IsConst) modopt(IsConst)) &local)));
                    }
                    fault
                    {
                        ___CxxCallUnwindDtor(std.basic_string<char,std::char_traits<char>,std::allocator<char> >.{dtor}, (void*) &local);
                    }
                }
                catch when (?)
                {
                }
                if (num != 0)
                {
                    throw;
                }
            }
            finally
            {
                __CxxUnregisterExceptionObject((void*) num2, (int) num);
            }
        }
        catch when (?)
        {
            num = 0;
            __CxxRegisterExceptionObject((void*) Marshal.GetExceptionPointers(), (void*) num2);
            try
            {
                try
                {
                    throw new ActivatorException("Unkown exception");
                }
                catch when (?)
                {
                }
                if (num != 0)
                {
                    throw;
                }
            }
            finally
            {
                __CxxUnregisterExceptionObject((void*) num2, (int) num);
            }
        }
    }
    fault
    {
        if (num3 == 0)
        {
            ___CxxCallUnwindDtor(ActivatorLib.cSerialNumber.{dtor}, (void*) &number);
        }
    }
    ActivatorLib.cSerialNumber.{dtor}(&number);
    num3 = 0;
    try
    {
        num4 = 0;
    }
    fault
    {
        if (num3 == 0)
        {
            ___CxxCallUnwindDtor(ActivatorLib.cSerialNumber.{dtor}, (void*) &number);
        }
    }
Label_01FC:
    return (bool) num4;
}

This is the file: http://www.mediafire.com/?3iqtjd3q3jsm9rr
I'd like to try keygenning this, but I'm so newbie I don't know what the statements starting with __ do. Plus I don't know how can I see the native code in ActivatorLib.cSerialNumber.IsValid.

[return: MarshalAs(UnmanagedType.U1)]
[PreserveSig, MethodImpl(MethodImplOptions.Unmanaged, MethodCodeType=MethodCodeType.Native), SuppressUnmanagedCodeSecurity]
public static unsafe bool modopt(CallConvThiscall) ActivatorLib.cSerialNumber.IsValid(cSerialNumber modopt(IsConst)* modopt(IsConst) modopt(IsConst));

Is there a way to know the offset of that native code to see it?
Pointers in the right direction will be greatly appreciated. Thanks!

[kao]

To get address of unmanaged functions, you can use ILDASM.
You'll see something like this:

.method public static pinvokeimpl(/* No map */) 
        bool modopt([mscorlib]System.Runtime.CompilerServices.CallConvThiscall) 
        marshal( unsigned int8) 
        MemoQ.ActivatorLib.cSerialNumber.IsValid(valuetype MemoQ.ActivatorLib.cSerialNumber modopt([mscorlib]System.Runtime.CompilerServices.IsConst)* modopt([mscorlib]System.Runtime.CompilerServices.IsConst) modopt([mscorlib]System.Runtime.CompilerServices.IsConst) A_0) native unmanaged preservesig
{
  .custom instance void [mscorlib]System.Security.SuppressUnmanagedCodeSecurityAttribute::.ctor() = ( 01 00 00 00 ) 
  // Embedded native code
  // Disassembly of native methods is not supported.
  //  Managed TargetRVA = 0x00025790
} // end of global method MemoQ.ActivatorLib.cSerialNumber.IsValid

So, the RVA you're looking for is 0x25790.

[Marton]

MANY thanks kao for the tip!! I will start looking there