Double array Managed to Unmanaged

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Hi,

I am newbie in C++ programming. I work on small app which does high frequecy calculations. Application is programmed in C# however I want to amend C++ native library that would be cosumed by managed code. And would be implementable in C#. I am trying to pin pointers to managed to unmanaged, I am however unsure how to proceed with pinning

C++

System::Double^ FSStat::Average(System::Double data[], int x1, int x2 )
{
	UnmanagedArrayPointer* DataArray = GetUnmanagedArrayPointer(data);
	double* unRes = st->Average(DataArray->Data, x1, x2);
	System::Double^ res = gcnew Double(*unRes);
	delete unRes;
	delete DataArray;
	return res;
}

UnmanagedArrayPointer* FSStat::GetUnmanagedArrayPointer( System::Double data[] )
{
    double* arr = new double[sizeof(data)];
    for (int i = 0; i<sizeof(data); i++)
    {
        pin_ptr<double> pinned = &arr[i];
        data[i]->CopyToBuffer(pinned);

    }
	UnmanagedArrayPointer* res = new UnmanagedArrayPointer(arr* , data.Length);
	return res;
}

Error 1 error C2227: left of '->CopyToBuffer' must point to class/struct/union/generic type E:\C#\Aerion Workstation\FinStatsLib\FSStat.cpp 35 1 FinStatsLib

Could somebody advice me how may I proceed with this. Your help would be much appreciated.

With best regards,
Jakub

Posted 2-Mar-12 2:06am

KubikKE

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Philippe Mori 2-Mar-12 19:41pm

I don't understand what you are trying to do. Code samples does not make much sense (too complicate and improper use of managed/unmanaged types). See my solution for some hints.

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Richard MacCutchan · Answer 1 · 2012-03-02T02:50:00

Solution 1

Firstly the following is wrong:

C++

double* arr = new double[sizeof(data)];

This will not get the size of the array passed in to this method, but the size of a pointer. You will need an extra parameter that gives the array size.
Secondly, the following line is wrong:

C++

data[i]->CopyToBuffer(pinned);

because System::Double[^] does not contain a CopyToBuffer() method.

Posted 2-Mar-12 2:50am

Richard MacCutchan

Comments

KubikKE 2-Mar-12 12:11pm

Ah ok, so System::Double data[] does not actually behave as array<system::double>? so if I use this instead? would i be able to use data->Length ?
I have seen some componenet stuff where CopyToBuffer() function was used.

What I actually want is to avoid copying of the value what is being done by marshalizing if I understood well. I would like to pin pointer only. Any thoughts about how can I proceed?

Managed C++ -> if I have library with function with parameters array<double>, would I be entering System.Double[] variable or do I need to use System::Double[^] parameter

Richard MacCutchan 2-Mar-12 15:19pm

I'm no expert in managed/unmanaged code, so would refer you to the P/Invoke tutorial for more information on marshalling. Although it has a slant towards C# it is still relevant to managed C++.

Philippe Mori 2-Mar-12 19:38pm

In C++/CLI, [] is used to declare unmanaged arrays (as in standard C++). You have to uses cli::array for managed arrays.

Richard MacCutchan 3-Mar-12 5:04am

Don't tell me, tell the questioner.

Philippe Mori · Answer 2 · 2012-03-02T13:54:00

As far as I know, you can pin a pointer (How to: Pin Pointers and Arrays[^]) from a cli::array[^], call unmanaged code and then get back the result.

And for such scenario, it is probably not even necessary to use C++/CLI as you can use P/Invoke from C#.

Calling Win32 DLLs in C# with P/Invoke[^]