Question

我正在尝试通过将open source library, written in C包裹起来并将其暴露给.Net来使用它。我决不是C专家。

到目前为止，我已经设法从F＃调用用C编写的演示代码。通过遵循this guide，然后填补空白，我设法做到了这一点。我已经改编了C代码以期望将int传递给它，因此我至少可以将F＃的标量值传入C。但是没有返回值。

但是处理数组要复杂得多。

我的C代码是

extern "C"
{
    __declspec(dllexport) void DisplayHelloFromDLL(int i)
    {
        //printf("Hello from DLL !\n");
        cout << "You gave me ... an int: " << i << endl;

        // Load problem data
        c_float P_x[4] = { 4., 1., 1., 2., }; //covariance matrix
        c_int   P_nnz = 4; //number of non-zero elements in covar
        c_int   P_i[4] = { 0, 1, 0, 1, }; //row indices?
        c_int   P_p[3] = { 0, 2, 4}; //?
        c_float q[2] = { 1., 1., }; //linear terms
        c_float A_x[4] = { 1., 1., 1., 1., }; //constraint coefficients matrix
        c_int   A_nnz = 4; //number of non zero elements in constraints matrix
        c_int   A_i[4] = { 0, 1, 0, 2, }; //row indices?
        c_int   A_p[3] = { 0, 2, 4}; //?
        c_float l[3] = { 1., 0., 0., }; //lower bounds
        c_float u[3] = { 1., 0.7, 0.7, }; //upper bounds
        c_int n = 2; //number of variables (x)
        c_int m = 3; //number of constraints


        // Problem settings
        OSQPSettings *settings = (OSQPSettings *)c_malloc(sizeof(OSQPSettings));

        // Structures
        OSQPWorkspace *work; // Workspace
        OSQPData *data;      // OSQPData

        // Populate data
        data = (OSQPData *)c_malloc(sizeof(OSQPData));
        data->n = n;
        data->m = m;
        data->P = csc_matrix(data->n, data->n, P_nnz, P_x, P_i, P_p);
        data->q = q;
        data->A = csc_matrix(data->m, data->n, A_nnz, A_x, A_i, A_p);
        data->l = l;
        data->u = u;


        // Define Solver settings as default
        osqp_set_default_settings(settings);

        // Setup workspace
        work = osqp_setup(data, settings);

        // Solve Problem
        osqp_solve(work);

        // Clean workspace
        osqp_cleanup(work);
        c_free(data->A);
        c_free(data->P);
        c_free(data);
        c_free(settings);
    }
}

我的C＃代码是

class Program
    {
        [DllImport("TestLibCpp.dll")]
        public static extern void DisplayHelloFromDLL(int i);
        static void Main(string[] args)
        {
            Console.WriteLine("This is F# program");
            DisplayHelloFromDLL(52);
        }
    }

为使此问题的重点保持狭窄：我如何将P_x设置为要从F＃传递的参数？

Answer 1

阅读AlexF的链接并开始工作后，我认为我会在这里为有类似问题的任何人提供答案。我可能会误解某些概念，但是代码可以正常工作。如果我弄错了任何细节，请告诉我，我将进行编辑。

要注意的概念：可漂白类型：这些类型在.Net（托管）和C（非托管）中具有相同的内部表示形式。可调度类型由封送拆收器“固定”，这似乎意味着将指针从.Net传递到C，而不是复制值。 Blittable类型的内存位置被锁定，直到返回非托管函数为止。不确定这会如何影响垃圾收集。

输入/输出属性：可填充数组作为输入参数传递。如果要使用它们作为返回值，则必须将它们明确标记为Out。

无论如何，这是有效的代码。

不受管理：

extern "C"
{
    __declspec(dllexport) void DisplayHelloFromDLL(c_float* P_x)
    {
        //printf("Hello from DLL !\n");
        //cout << "You gave me ... an int: " << i << endl;

        // Load problem data
        //c_float P_x[4] = { 4., 1., 1., 2., }; //covariance matrix
        c_int   P_nnz = 4; //number of non-zero elements in covar
        c_int   P_i[4] = { 0, 1, 0, 1, }; //row indices?
        c_int   P_p[3] = { 0, 2, 4}; //?
        c_float q[2] = { 1., 1., }; //linear terms
        c_float A_x[4] = { 1., 1., 1., 1., }; //constraint coefficients matrix
        c_int   A_nnz = 4; //number of non zero elements in constraints matrix
        c_int   A_i[4] = { 0, 1, 0, 2, }; //row indices?
        c_int   A_p[3] = { 0, 2, 4}; //?
        c_float l[3] = { 1., 0., 0., }; //lower bounds
        c_float u[3] = { 1., 0.7, 0.7, }; //upper bounds
        c_int n = 2; //number of variables (x)
        c_int m = 3; //number of constraints


        // Problem settings
        OSQPSettings *settings = (OSQPSettings *)c_malloc(sizeof(OSQPSettings));

        // Structures
        OSQPWorkspace *work; // Workspace
        OSQPData *data;      // OSQPData

        // Populate data
        data = (OSQPData *)c_malloc(sizeof(OSQPData));
        data->n = n;
        data->m = m;
        data->P = csc_matrix(data->n, data->n, P_nnz, P_x, P_i, P_p);
        data->q = q;
        data->A = csc_matrix(data->m, data->n, A_nnz, A_x, A_i, A_p);
        data->l = l;
        data->u = u;


        // Define Solver settings as default
        osqp_set_default_settings(settings);

        // Setup workspace
        work = osqp_setup(data, settings);

        // Solve Problem
        osqp_solve(work);

        // Clean workspace
        osqp_cleanup(work);
        c_free(data->A);
        c_free(data->P);
        c_free(data);
        c_free(settings);
    }
}

托管（F＃）

open System.Runtime.InteropServices

module ExternalFunctions =
    [<DllImport("TestLibCpp.dll")>]
    extern void DisplayHelloFromDLL(float[] i)

[<EntryPoint>]
let main argv = 
    let P_x = [|4.; 1.; 1.; 2.|]
    ExternalFunctions.DisplayHelloFromDLL(P_x);
    0 // return an integer exit code

如何将数组从.Net传递到C？

1 个答案: