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.NET 4 with 64bit. I have a C# structure that I intend to marshal to C

[StructLayout(LayoutKind.Sequential)]
public struct ParentStruct
{
    public float[] FArray;
    public int FArrayLength;
}

To 

struct ParentStruct
{
    float* FArray;
    int FArrayLength;
};

The special circumstances here is the array I need to copy float[] FArray is always pinned and has 0 elements and I am only interested in copying its pointer across to native and not interested in the actual elements it has (which are none!) nor in allocating memory on the native side on the free store (heap), it will be pointing to a garbage location, this is fine.

The technical reason for doing this is that float[] FArray is pointing to an address on the GPU memory and once it is marshaled to the GPU, it will be pointing to the right data.

I want to be able to marshal this struct to C, but I am not sure what is the proper marshal way

  • I tried marshaling it in the current structure, I got Object contains non-primitive or non-blittable data.
  • I tried adding [MarshalAs(UnmanagedType.LPArray)] and I was getting Type 'Test.ParentStruct' cannot be marshaled as an unmanaged structure; no meaningful size or offset can be computed.

By the way, I do understand why I am getting these errors, what I really want is a way to marshal given that my array is not a variable array (but it looks like one to the interop libraries) and you can think of my struct as a fixed size.

N.B. I have to use a float[] rather than a uint or something like that because of intellisense and other constraints.

Adam
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  • related question: http://stackoverflow.com/questions/1681517/marshalling-struct-with-embedded-pointer-from-c-sharp-to-unmanaged-driver – yms May 03 '13 at 19:31
  • @yms thank you for the note, however, I wanted to keep the float[] rather than changing it to another type (hence the N.B. in the end of my post). – Adam May 03 '13 at 20:13
  • I suspect you won't be able to do that... but maybe someone else knows better. – yms May 03 '13 at 20:17

0 Answers0