如何实现c++返回char**值传给C#

本篇内容主要讲解"如何实现c++返回char**值传给C#"，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习"如何实现c++返回char**值传给C#"吧!

char **arr; int arrlen,arrcol;templatevoid make2DArray(T** &ptr, int rows, int cols){        //创建二维数组，先创建行指针        ptr = new T*[rows];        //再为每一行分配空间        for (int i = 0; i < rows; i++)        {                ptr[i] = new T[cols];        }}void alloc2D(){        arrlen = 3;        arrcol = 2;        arr = new char*[arrlen];//分配3个元素的数组空间，每个元素是char*指针元素        for (int i = 0; i <= arrlen; i++)        {                arr[i] = new char[arrcol*(i+1)+1]; //其实不同行可以长度不同        }}void* returnpptr(int* len) //C++分配内存，返回**给C# {        alloc2D();        *len = 3;        for (int i = 0; i < arrlen; i++)        {                for (int j = 0; j <= arrcol*(i + 1)+1; j++)                {                        if (j == arrcol*(i + 1)+1)                                arr[i][j] = 0;                        else                                arr[i][j] = (char)(0x31 + i + j % 5);                }        }        return arr;}

[DllImport("dllfordebugdemo.dll", EntryPoint = "returnpptr", CallingConvention = CallingConvention.Cdecl)]        public static extern IntPtr returnpptr(ref int len);        private void button7_Click(object sender, EventArgs e)        {            int len =0;            IntPtr p = returnpptr(ref len);             IntPtr[] ps = new IntPtr[len];            for(int i =0;i
显示如下：
123
23456
3456734
如果C++返回的是int**，实验如下：
int** ppcol;int* p1;int reflen;void* returnpptrint(int* len){        reflen = 1;        *len = reflen;        arrcol = 2;        p1 = &arrcol;        if (ppcol == NULL)        {                ppcol = &p1;        }        return ppcol;}
[DllImport("dllfordebugdemo.dll", EntryPoint = "returnpptrint", CallingConvention = CallingConvention.Cdecl)]        public static extern IntPtr returnpptrint(ref int len);private void button7_Click(object sender, EventArgs e)        {            int len =0;            IntPtr p = returnpptrint(ref len);            IntPtr[] ps = new IntPtr[len];            int[] lens = new int[len];            for (int i = 0; i < len; i++)            {                ps[i] = Marshal.ReadIntPtr(p + Marshal.SizeOf(typeof(IntPtr)) * i);                Marshal.Copy(ps[i],lens,0,1);                Console.WriteLine("lens[i]=" + lens[i]);            }        }
显示：
lens[i]=2
总结：
C#无法接收C++返回值的char**/int**,只能先强转为void*,然后在C#中public static extern IntPtr fun(...)，实际使用时二级指针的行数，并且通过IntPtr[]数组和Marshal.ReadIntPtr（基址+偏址），再用Marshal.Copy或PtrToString...方式获取最终值。
到目前为止：三级指针不管是参数还是返回值形式，都不成功(估计还是以后有时间再做实验)。
上面统一以c# IntPtr接收C++的void*(实际是char**/int**强转而来），虽然实验成功，但换种思维方式，c++中还是char**/int** fun(...)，而c#中以IntPtr fun(...)可不可以呢？
[DllImport("dllfordebugdemo.dll", EntryPoint = "returnpptr", CallingConvention = CallingConvention.Cdecl)]        public static extern IntPtr returnpptr(ref int len);private void button7_Click(object sender, EventArgs e)        {            int len =0;            IntPtr p = returnpptr(ref len);            IntPtr[] ps = new IntPtr[len];            for (int i = 0; i < len; i++)            {                ps[i] = Marshal.ReadIntPtr(p + Marshal.SizeOf(typeof(IntPtr)) * i);                Console.WriteLine(Marshal.PtrToStringAnsi(ps[i]));            }}
void** returnpptr(int* len) //C++分配内存，返回**给C#{        alloc2D();        *len = 3;        for (int i = 0; i < arrlen; i++)        {                for (int j = 0; j <= arrcol*(i + 1)+1; j++)                {                        if (j == arrcol*(i + 1)+1)                                arr[i][j] = 0;                        else                                arr[i][j] = (char)(0x31 + i + j % 5);                }        }        return (void**)arr;}或者将返回值改为实际的char**:char** returnpptr(int* len) //C++分配内存，返回**给C#{        alloc2D();        *len = 3;        for (int i = 0; i < arrlen; i++)        {                for (int j = 0; j <= arrcol*(i + 1)+1; j++)                {                        if (j == arrcol*(i + 1)+1)                                arr[i][j] = 0;                        else                                arr[i][j] = (char)(0x31 + i + j % 5);                }        }        return (arr;}
C#中还是IntPtr returnpptr(ref int len)，最终实验也是成功的。
到此，相信大家对"如何实现c++返回char**值传给C#"有了更深的了解，不妨来实际操作一番吧！这里是网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！