Question

我正在制作一个c＃程序来绘制用c计算的三次样条曲线，这是程序的互操作部分

我的c＃代码：

    [DllImport(@"..\..\..\Debug\Spline_Core.dll")]
    static extern IntPtr mult_points(Point[] points, int points_count, double factor);

    public Form1()
    {
        InitializeComponent();

        var points = new[]
        {
            new Point { x = 2, y = 3 },
            new Point { x = 5, y = 7 },
        };

        var sum = mult_points(points, 2, 2);
        var mult = (Point[])Marshal.PtrToStructure(sum, typeof(Point[]));
    }

和c代码：

typedef struct point
{
    double x, y;
} Point;

extern __declspec(dllexport) Point* __stdcall mult_points(Point* points, int points_count, double factor)
{
    int i;

    Point* mult_points = (Point*)malloc(points_count * sizeof(Point));

    for (i = 0; i < points_count; i++)
        mult_points[i] = create_point(points[i].x * factor, points[i].y * factor);

    return mult_points;
}

我可以通过c＃到c的参数传递点数组，但是我无法将其取回。

Answer 1

从技术上讲，

Point*只是指向单个Point结构的指针。编组器不知道它是一个数组还是这个数组中有多少个元素。所以你的演员Point[]是错误的。

为了更好地理解，请参阅此简单示例 - 而不是此代码：

var sum = mult_points(points, 2, 2);
var mult = (Point[])Marshal.PtrToStructure(sum, typeof(Point[]));

......你可以使用这样的东西：

IntPtr sum = mult_points(points, 2, 2);
int structSize = Marshal.SizeOf(typeof(Point));
for (int i = 0; i < numberOfPoints; i++)
{
    IntPtr curr = sum + (i * structSize);
    Point pt = (Point)Marshal.PtrToStructure(curr, typeof(Point));
    // Add pt to List<Point> for example
}

这不是一个理想的解决方案，但我希望你明白这一点。可以在此处找到更好（更优雅）的解决方案：How do I marshall a pointer to a pointer of an array of structures?

将结构数组从c返回到c＃

1 个答案: