问C# P/Invoke和包含字节数组的结构数组
EN

Stack Overflow用户

提问于 2013-04-24 23:15:53

回答 3查看 1.8K关注 0票数 0

我需要从C#代码调用一个本机DLL。由于我对C/C++不太熟悉，所以我不知道如何在C#中声明在C中定义的结构以便调用它。问题是，两个参数似乎是一个结构数组，我不知道如何在C#中声明它(参见最后一个代码块)：

c++头文件：

typedef enum
{   
    OK = 0,
    //others
} RES

typedef struct
{
    unsigned char* pData;
    unsigned int length;
} Buffer;

RES SendReceive(uint32 deviceIndex
    Buffer* pReq,
    Buffer* pResp,
    unsigned int* pReceivedLen,
    unsigned int* pStatus);

c#声明：

enum
{   
    OK = 0,
    //others
} RES

struct Buffer
{
    public uint Length;
    public ??? Data; // <-- I guess it's byte[]
}

[DllImport("somemodule.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern uint SendReceive(
    uint hsmIndex,
    uint originatorId,
    ushort fmNumber,
    ??? pReq,  // <-- should this be ref Buffer[] ?
    uint reserved,
    ??? pResp, // <-- should this be ref Buffer[] ?
    ref uint pReceivedLen,
    ref uint pFmStatus);

在一个等价的java客户机中，我发现参数不仅仅是一个缓冲区，而是一个缓冲区数组。在C#中，它看起来如下所示：

 var pReq = new Buffer[] 
{
    new Buffer { Data = new byte[] { 1, 0 }, Length = (uint)2 }, 
    new Buffer {Data = requestStream.ToArray(), Length = (uint)requestStream.ToArray().Length },
    //according to the header file, the last item must be {NULL, 0}
    new Buffer { Data = null, Length = 0 }
};

var pResp = new Buffer[] 
{
    new Buffer { Data = new byte[0x1000], Length = 0x1000 }, 
    //according to the header file, the last item must be {NULL, 0}
    new Buffer { Data = null, Length = 0x0 }
};

这对我来说很奇怪，因为extern方法确实有一个指向缓冲区结构( Buffer *)的指针，而不是一个指向缓冲区数组(Buffer[]*)的指针。如何在C#中定义结构和extern方法的参数类型？

任何帮助都很感谢，谢谢。

interop

pinvoke

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回答 3

Stack Overflow用户

回答已采纳

发布于 2013-04-24 23:34:35

首先，您的结构以错误的顺序获得参数。需要将字节数组声明为IntPtr，并手动编组：

struct Buffer
{
    public IntPtr Data;
    public uint Length;
}

p/invoke应是：

[DllImport("MyNativeDll.dll", CallingConvention=CallingConvention.Cdecl)]
static extern RES SendReceive(
    uint deviceIndex, 
    [In] Buffer[] pReq, 
    [In, Out] Buffer[] pResp, 
    out uint pReceivedLen, 
    out uint pStatus
);

字节数组需要是IntPtr，这样结构才是可闪烁的。这是必需的，这样数组参数就可以声明为Buffer[]。

做字节数组的编组工作会有点痛苦。您将希望使用GCHandle来插入托管字节数组，并调用AddrOfPinnedObject()来获取结构数组中每个结构的固定数组的地址。编写一些帮助函数以减轻任务的痛苦是值得的。

票数 2

Stack Overflow用户

发布于 2013-04-24 23:28:49

c#中的方法签名应该如下所示：

[DllImport("MyNativeDll.dll")]
public static extern RES SendReceive (uint32 deviceIndex, ref Buffer pReq, ref Buffer pResp, ref uint pReceivedLen, ref uint pStatus);

请参阅此项目，将来您可能会从.net http://clrinterop.codeplex.com/releases/view/14120生成本机调用。

票数 0

Stack Overflow用户

发布于 2013-04-24 23:52:20

基于C++头，但不进行测试，请查看以下代码：

using System;
using System.Runtime.InteropServices;
using System.Text;

namespace WindowsFormsApplication1
{
    public class Class1
    {
        public struct Buffer
        {
            [MarshalAs(UnmanagedType.LPStr)]
            public StringBuilder pData;

            public uint length;
        }

        [DllImport("kernel32.dll", EntryPoint = "LoadLibrary")]
        static extern int LoadLibrary(string lpLibFileName);

        [DllImport("kernel32.dll", EntryPoint = "GetProcAddress")]
        static extern IntPtr GetProcAddress(int hModule, string lpProcName);

        [DllImport("kernel32.dll", EntryPoint = "FreeLibrary")]
        static extern bool FreeLibrary(int hModule);

        [UnmanagedFunctionPointer(CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        internal delegate IntPtr SendReceive(
            uint deviceIndex,
            ref Buffer pReq,
            ref Buffer pResp,
            uint pReceivedLen,
            uint pStatus);

        public void ExecuteExternalDllFunction()
        {
            int dll = 0;

            try
            {
                dll = LoadLibrary(@"somemodule.dll");
                IntPtr address = GetProcAddress(dll, "SendReceive");

                uint deviceIndex = 0;
                Buffer pReq = new Buffer() { length = 0, pData = new StringBuilder() };
                Buffer pResp = new Buffer() { length = 0, pData = new StringBuilder() };
                uint pReceivedLen = 0;
                uint pStatus = 0;

                if (address != IntPtr.Zero)
                {
                    SendReceive sendReceive = (SendReceive)Marshal.GetDelegateForFunctionPointer(address, typeof(SendReceive));

                    IntPtr ret = sendReceive(deviceIndex, ref pReq, ref pResp, pReceivedLen, pStatus);
                }
            }
            catch (Exception Ex)
            {
                //handle exception...
            }
            finally
            {
                if (dll > 0)
                {
                    FreeLibrary(dll);
                }
            }
        }
    }
}