用于 C 结构和函数的 C# 编码

Question

我有以下 C 头文件/代码示例:

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头文件

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struct category_info {
 int id;
 const char *name;
 const char *description;
};


DLLEXPORT
void* xyz_categories_info(struct category_info **info, size_t *info_count);

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示例 C 代码段

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struct category_info *catinfo;

size_t catcount;
size_t i;
int max_name_len = 0;
void *catmem = xyz_categories_info(&catinfo, &catcount)

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我想将其转换为 C#...

我的第一个猜测(也是一个猜测)是:

[StructLayout(LayoutKind.Sequential)]
    public struct category_info
    {
        int id;
        [MarshalAs(UnmanagedType.LPStr)]
        StringBuilder name;
        [MarshalAs(UnmanagedType.LPStr)]
        StringBuilder description;
    };

[DllImport("mydll.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
public static extern IntPtr xyz_categories_info([Out]category_info cat, [Out]int catSize);

但它看起来不对..

任何建议.. 一旦在 C# 中正确声明了上述内容.. 应该如何在 C# 中访问它

category_info catinfo;

catmem = xyz_categories_info(out catinfo, out catcount);

??????

非常感谢任何帮助。

谢谢

============================================= =================================

更新2

xyz_categories_info 中分配的内存使用此 C 调用释放:

void xyz_categories_info_free(void *p);

下面是一个在 C 中使用它的例子....希望这能解释得更多一点..

    category_buffer = xyz_categories_info(&category_info, &category_count);

if( !category_buffer ) 
    {
    // Failed Log a message and exit.
    exit(1);
}

for(j=0; j<category_count; j++) 
    {
    if( category_info[j].id == 0 )
        continue;

    printf("id: %d name: '%s' description: '%s'\n",
        category_info[j].id,
        category_info[j].name,
        category_info[j].description
    );
}

xyz_categories_info_free(category_buffer);

Answer 1

此代码已编译，但未经过测试。如果您了解 C，就会明白这里发生了什么，这只是将相同的 C 代码转换为 C#。

using System;using System.Collections.Generic;using System.Text;using System.Runtime.InteropServices;namespace ConsoleApplication1{    public struct category_info     {         public int id;        public IntPtr name;        public IntPtr description;    };     class Program    {        [DllImport("mydll.dll", CallingConvention = CallingConvention.Cdecl)]        public static extern IntPtr xyz_categories_info(ref IntPtr cat, ref int catSize);        [DllImport("mydll.dll", CallingConvention = CallingConvention.Cdecl)]        public static extern void xyz_categories_info_free(IntPtr cat);         static void Main(string[] args)        {            IntPtr categories = IntPtr.Zero;            IntPtr category_buffer = IntPtr.Zero;            int category_count = 0;            category_info info = new category_info();            IntPtr current;            try            {                category_buffer = xyz_categories_info(ref categories, ref category_count);                if (category_buffer == IntPtr.Zero)                {                    return;                }                if (category_count == 0)                {                    return;                }                for (int j = 0; j < category_count; j++)                {                    if (IntPtr.Size == 4)                    {                        current = new IntPtr(categories.ToInt32() + j * Marshal.SizeOf(info));                    }                    else                    {                        current = new IntPtr(categories.ToInt64() + j * Marshal.SizeOf(info));                    }                    info = (category_info)Marshal.PtrToStructure(current, typeof(category_info));                    if (info.id == 0)                    {                        continue;                    }                    Console.WriteLine(info.id);                    Console.WriteLine(Marshal.PtrToStringAnsi(info.name));                    Console.WriteLine(Marshal.PtrToStringAnsi(info.description));                }            }            finally            {                if (category_buffer != IntPtr.Zero)                {                    xyz_categories_info_free(category_buffer);                }            }        }    }}