如何返回从 Rust 到 C# 的整数数组？

Question

I'm trying to use this Rust function in C#:

pub extern fn get_possible_moves(i: i8, j: i8, k: i8) -> [i8; 512]

I wrote this signature in the C# code:

[DllImport("my_library")]
private static extern sbyte[] get_possible_moves(sbyte i, sbyte j, sbyte k);

This doesn't work:

Unhandled exception. System.Runtime.InteropServices.MarshalDirectiveException: Cannot marshal 'return value': Invalid managed/unmanaged type combination.

Is the method signature incorrect?

Answer 1

Assuming Rust exports a C-style array, the marshaler would not be able to convert it to a managed array since it does not know the length. There seem to be two options:

• Add an attribute to tell the marshaler how long the array is : [MarshalAs(UnmanagedType.LPArray, SizeConst=512)]
• Change the return type to an IntPtr and convert it to an array by hand. See ToPointer . Keep in mind that the returned memory might need to be de-allocated, somehow.