I've written a dll in C which has functions I can call when referencing the DLL in C#. If I use a basic type like an int it works fine, but I have structs which are slightly different in C# than they are in C due to language differences. Here is an example. This is the function definition in C#:
[DllImport("hello_world_cuda.dll", CharSet = CharSet.Auto)]
public static extern Batch Cut();
And here is it in C:
extern "C" Batch __declspec(dllexport) __stdcall Cut()
You can see the return type Batch is the same, but here is its definition in C#
class Envelope
{
public byte[] Payload;
public byte[] Signature;
}
class Batch
{
public Envelope[] Messages;
public int MsgCount;
}
And here is the definition in C
struct Envelope
{
public:
char* Payload;
char* Signature;
};
struct Batch
{
public:
Envelope* Messages;
int MsgCount;
};
How do I overcome these language differences in order to successfully make the DLL call in C#?
Pointers in an unmanaged language do not map to managed arrays as you have done, this is why it is complaining. char is (almost always, with very limited exceptions) an 8 bit value that maps well to byte in C# as you've noticed, but you need to make them pointers in the managed struct as well:
unsafe struct Envelope
{
public byte* Payload;
public byte* Signature;
}
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