Calling C++ Library from C# with C++/CLI Wrapper
I have a C++ library, header of which looks like:
void NotMyFun(double * a, int * b);
The function reads from a , and writes to b . To call the library I have created a C++/CLI wrapper, where below function is defined:
static void MyWrapperFun(double * a, int * b)
{
NotMyFun(a,b);
}
and works OK. From C# code, say, I have two managed arrays, ie double[] ma and double[] mb , where ma already holds some meaningful data, and mb is -meaningfully- filled when wrapper is called. Is below an OK way to call the wrapper function?
unsafe
{
fixed (double* pma = ma)
{
fixed (int* pmb = mb)
{
MyWrapperNS.MyWrapperClass.MyWrapperFun(pma,pmb);
}
}
}
Are the unsafe pointers a fast way? Is any data copying involved here while passing and retrieving to/from C++/CLI wrapper? Or pointers are already pointing to a continuous memory space in C# arrays?
Besides, do I need any manual memory cleaning here? If the pointers are tied to the memory of managed C# arrays, I guess they are properly garbage collected after, but just want to be sure.
Personally I think you are over-complicating things. I'd avoid the unsafe code and skip the C++/CLI layer. I'd use a simple p/invoke declared like this:
[DllImport(@"mylib.dll")]
static extern void NotMyFun(double[] a, int[] b);
Because double and int are blittable types, no copying is necessary. The marshaller just pins the arrays for the duration of the call.
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