c# - 尝试在 c# 中使用 dllimport 读取或写入 protected 内存

Question

我的项目有问题:在 dll C++ 中:

    extern "C" __declspec(dllexport) int results(char* imgInput, void* tree)
{   
    struct kd_node* nodeTree = new(tree)kd_node ; // new kd_tree with data from memory address
    ...

    ...
    int ret = atoi(retValueStr.c_str());
    return ret;
}

extern "C" __declspec(dllexport) void* buildKDTree(char* folder)
{
    struct kd_node* kd_root;
    ....

    feature *LFData = listFeat.data();
    kd_root = kdtree_build(LFData,listFeat.size());
    void* address_kdtree = (void*)&kd_root; // get memory address of kd_tree
    return address_kdtree;
}

我在 C# 中使用 dllimport:

[DllImport(@"kdtreeWithsift.dll", EntryPoint = "buildKDTree", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
public unsafe static extern void* buildKDTree(byte[] urlImage);


[DllImport(@"kdtreeWithsift.dll", EntryPoint = "results", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
[return:MarshalAs(UnmanagedType.I4)]
public unsafe static extern int results(byte[] imgInput, void* tree);

static unsafe void Main()
{
     string urlImg1 = "C:/Users../test img/1202001T1.jpg";
     string urlImg = "C:/export_features"; 

     try
     {  
     IntPtr result;
     int result1;
     result1 = results(convertStringToByte(urlImg1), 5, buildKDTree(convertStringToByte(urlImg))); //  this error
     Console.WriteLine("results = %d",result1);
     }
     catch (Exception ex)
     {
          Console.WriteLine(ex);
          Console.ReadLine();
     }
}

当我运行该程序时，该程序显示错误:尝试读取或写入 protected 内存。这通常表明其他内存已损坏

您知道什么错误以及如何解决？谢谢!

Answer 1

此处不需要convertStringToByte 方法。您可以告诉运行时将您的字符串编码为 char *。另外，我建议您让该方法返回一个 IntPtr，如下所示:

[DllImport(@"kdtreeWithsift.dll", EntryPoint = "buildKDTree",
    CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
public static extern IntPtr buildKDTree([MarshalAs(UnmanagedType.LPStr)]string urlImage);

[DllImport(@"kdtreeWithsift.dll", EntryPoint = "results",
    CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
[return:MarshalAs(UnmanagedType.I4)]
public static extern int results([MarshalAs(UnmanagedType.LPStr)]string imgInput, IntPtr tree);

然后你可以调用它:

IntPtr tree = buildKDTree(urlImg);
int result1 = results(urlImg, 50, tree);

Console.WriteLine("results = {0}",result1);