.Net Interop Example

interop.cpp

#include <cstdio>
#include <cstdint>
#include <cstring>
#include <cstdlib>

extern "C" {

struct StandardStructure {
    std::int32_t a;
    float b;
    char *c;
};

bool ValStructure(StandardStructure s)
{
    std::printf("[C] a: %d, b: %f, c: %s\n", s.a, s.b, s.c);
    return true;
}

bool PtrStructure(StandardStructure *s)
{
    std::printf("[C] a: %d, b: %f, c: %s\n", s->a, s->b, s->c);
    return true;
}

typedef bool (*ValStructureCallback_t)(StandardStructure);
typedef bool (*PtrStructureCallback_t)(StandardStructure *);

static ValStructureCallback_t __valStructureCallback;
static PtrStructureCallback_t __ptrStructureCallback;

void SetValStrCallback(ValStructureCallback_t callback)
{
    __valStructureCallback = callback;
}

void SetPtrStrCallback(PtrStructureCallback_t callback)
{
    __ptrStructureCallback = callback;
}

void RunValCallback()
{
    auto S = "RunValCallback";
    auto s = strdup(S);

    StandardStructure str;
    str.a = 9999;
    str.b = 2333.3333;
    str.c = s;
    bool ret = __valStructureCallback(str);
    std::printf("[C]Result: %s", ret ? "true" : "false");
}

void RunPtrCallback()
{
    auto S = "RunPtrCallback";
    auto s = strdup(S);

    StandardStructure str;
    str.a = 8888;
    str.b = 3444.4444;
    str.c = s;
    bool ret = __ptrStructureCallback(&str);
    std::printf("[C]Result: %s", ret ? "true" : "false");
}

}

interop.cs

using System;

using System.Runtime.InteropServices;  



namespace cs

{

    [StructLayout(LayoutKind.Sequential)]

    public struct Structure {

        public int first;

        public float second;

        public String third;

    }



    class Program
    {

        [DllImport("main")]
        public static extern bool ValStructure(Structure str);

        [DllImport("main")]
        public static extern bool PtrStructure(ref Structure str);
        
        public delegate bool ValStructureCallback(Structure structure);
        public delegate bool PtrStructureCallback(ref Structure structure);

        [DllImport("main")]
        public static extern bool SetValStrCallback(ValStructureCallback callback);

        [DllImport("main")]
        public static extern bool SetPtrStrCallback(PtrStructureCallback callback);

        [DllImport("main")]
        public static extern void RunValCallback();

        [DllImport("main")]
        public static extern void RunPtrCallback();

        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
            var str1 = new Structure();
            str1.first = 7777;
            str1.second = 8888.8888f;
            str1.third = "First!!!!";

            SetValStrCallback(s => {
                Console.WriteLine($"[#]V a: {s.first}, b: {s.second}, c: {s.third}");
                return true;
            });

            SetPtrStrCallback((ref Structure s) => {
                Console.WriteLine($"[#]P a: {s.first}, b: {s.second}, c: {s.third}");
                return false;
            });

            RunValCallback();
            RunPtrCallback();
        }
    }
}

interop.csproj

<Project Sdk="Microsoft.NET.Sdk">



  <PropertyGroup>

    <OutputType>Exe</OutputType>

    <TargetFramework>netcoreapp2.0</TargetFramework>

  </PropertyGroup>



</Project>

Makefile

all:
	g++ -shared interop.cpp -o libmain.so