c# P/Invoke和包含字节数组的结构数组

本文关键字：数组 字节数 结构 字节 包含 Invoke | 更新日期: 2023-09-27 18:11:00

我需要从c#代码调用本地DLL。由于我对C/c++不太熟悉，我不知道在C中定义的结构应该如何在c#中声明，以便可以调用它。问题是两个参数似乎是一个结构体数组，我不知道如何在c#中声明这个(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);

在一个等效的java客户端中，我发现参数不仅仅是一个Buffer，而是一个Buffer数组。在c#中，它看起来像这样:

 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 }
};

这对我来说似乎很奇怪，因为extern C方法确实有一个指向Buffer结构体(Buffer*)的指针，而不是指向Buffer数组(Buffer[]*)的指针。如何在c#中定义Struct和extern方法的参数类型?

感谢您的帮助。

c# P/Invoke和包含字节数组的结构数组

首先，结构体的参数顺序错误。并且字节数组需要通过手动封送声明为IntPtr:

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

p/调用应该是:

[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，这样结构体是可比特的。这是必要的，以便数组参数可以声明为Buffer[]。

对字节数组进行编组将会有点麻烦。您需要使用GCHandle来固定托管字节数组，并调用AddrOfPinnedObject()来获取结构数组中每个结构的固定数组的地址。在编写一些帮助函数以使该任务不那么痛苦时，这将是值得的。

你在c#中的方法签名应该是这样的:

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

看看这个项目，它可能会帮助你在未来从。net生成原生调用http://clrinterop.codeplex.com/releases/view/14120

基于c++头文件，但没有经过测试，请看下面的代码:

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);
                }
            }
        }
    }
}
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