需要将指针从 VB.NET 传递到 C++/CLR

Question

我正在尝试创建一个 C++/CLR 项目以使用 IPHlpApi.dll 的 SendARP 方法。该函数需要一个指向 ULONG 变量数组的指针。我不确定如何实现或解决它。

MSDN 信息：

DWORD SendARP(
  _In_     IPAddr DestIP,
  _In_     IPAddr SrcIP,
  _Out_    PULONG pMacAddr,
  _Inout_  PULONG PhyAddrLen
);

pMacAddr [out]
A pointer to an array of ULONG variables. This array must have at least two ULONG elements to hold an Ethernet or token ring physical address. The first six bytes of this array receive the physical address that corresponds to the IPv4 address specified by the DestIP parameter.

这就是我的包装类中的内容。 IPAddr 和 PULONG 都是 typedef unsigned long 以便让 VB.Net 识别我已将它们转换为 ULONG 的类型。据我所知，其他 3 个参数都很好，我只需要更改 pMacAddr 并以某种方式从 VB 传递一个指针（或找到解决方法）。

ULONG SendARPRequest(ULONG DestIP, ULONG SrcIP, ULONG pMacAddr, ULONG PhyAddrLen) { return ULONG (m_nativeClass->SendARPRequest(IPAddr (DestIP), IPAddr(SrcIP), PULONG(pMacAddr), PULONG (PhyAddrLen))); };

如果您需要更多我的代码，请询问。我不想不必要地填补这个职位。提前致谢。

编辑：

Wrapper.h

#include <Windows.h>
#include <winerror.h>
#include <IPHlpApi.h>
#include "IPHelper.h"
#pragma comment(lib, "IPHLPAPI.lib")


using namespace System;

public ref class NativeClassWrapper {
    IPHelper* m_nativeClass;

public:
    static const ULONG IPH_NO_ERROR = NO_ERROR;
    static const ULONG IPH_ERROR_BAD_NET_NAME = ERROR_BAD_NET_NAME; // The network name cannot be found. This error is returned on Windows Vista and later when an ARP reply to the SendARP request was not received. This error occurs if the destination IPv4 address could not be reached because it is not on the same subnet or the destination computer is not operating.
    static const ULONG IPH_ERROR_BUFFER_OVERFLOW = ERROR_BUFFER_OVERFLOW; // The file name is too long. This error is returned on Windows Vista if the ULONG value pointed to by the PhyAddrLen parameter is less than 6, the size required to store a complete physical address.
    static const ULONG IPH_ERROR_GEN_FAILURE = ERROR_GEN_FAILURE; //A device attached to the system is not functioning. This error is returned on Windows Server 2003 and earlier when an ARP reply to the SendARP request was not received. This error can occur if destination IPv4 address could not be reached because it is not on the same subnet or the destination computer is not operating.
    static const ULONG IPH_ERROR_INVALID_PARAMETER = ERROR_INVALID_PARAMETER; //One of the parameters is invalid. This error is returned on Windows Server 2003 and earlier if either the pMacAddr or PhyAddrLen parameter is a NULL pointer.
    static const ULONG IPH_ERROR_INVALID_USER_BUFFER = ERROR_INVALID_USER_BUFFER; //The supplied user buffer is not valid for the requested operation. This error is returned on Windows Server 2003 and earlier if the ULONG value pointed to by the PhyAddrLen parameter is zero.
    static const ULONG IPH_ERROR_NOT_FOUND = ERROR_NOT_FOUND; //Element not found. This   error is returned on Windows Vista if the the SrcIp parameter does not specify a source IPv4 address on an interface on the local computer or the INADDR_ANY IP address (an IPv4 address of 0.0.0.0).
    static const ULONG IPH_ERROR_NOT_SUPPORTED = ERROR_NOT_SUPPORTED; //The SendARP function is not supported by the operating system running on the local computer.

public:
    NativeClassWrapper() { m_nativeClass = new IPHelper(); }
    ~NativeClassWrapper() { this->!NativeClassWrapper(); }
    !NativeClassWrapper() { delete m_nativeClass; }

    //DWORD SendARPRequest(IPAddr DestIP, IPAddr SrcIP, PULONG pMacAddr, PULONG PhyAddrLen) { return m_nativeClass->SendARPRequest(DestIP, SrcIP, pMacAddr, PhyAddrLen); };
    ULONG SendARPRequest(ULONG DestIP, ULONG SrcIP, ULONG pMacAddr, ULONG PhyAddrLen) { return ULONG (m_nativeClass->SendARPRequest(IPAddr (DestIP), IPAddr(SrcIP), PULONG(pMacAddr), PULONG (PhyAddrLen))); };

};

IPHelper.h

public class IPHelper {
public:
    DWORD SendARPRequest(IPAddr DestIP, IPAddr SrcIP, PULONG pMacAddr, PULONG PhyAddrLen);  
};

IPHelper.cpp

#include "stdafx.h"
#include "Wrapper.h"

//DWORD IPHelper::SendARPRequest(IPAddr DestIP, IPAddr SrcIP, PULONG pMacAddr, PULONG PhyAddrLen) {
DWORD IPHelper::SendARPRequest(IPAddr DestIP, IPAddr SrcIP, PULONG pMacAddr, PULONG PhyAddrLen) {
    return SendARP(DestIP, SrcIP, pMacAddr, PhyAddrLen);
};

Answer 1

查看SendARP 的文档以及pinvoke.net 的示例，我们可以编写这样的C++/CLI 代码来调用它：

public ref class NativeClassWrapper
{
public:

    static String^ SendARPRequest(String^ dest, String^ source)
    {
        marshal_context ctx;

        IPAddr DestIp = inet_addr(ctx.marshal_as<const char *>(dest));
        IPAddr SrcIp = inet_addr(ctx.marshal_as<const char *>(source));

        ULONG MacAddr[2];
        ULONG PhysAddrLen = 6;
        memset(&MacAddr, 0xff, sizeof(MacAddr));

        DWORD dwRetVal = SendARP(DestIp, SrcIp, &MacAddr, &PhysAddrLen);

        array<String^>^ str = gcnew array<String^>(PhysAddrLen);
        for (int i = 0; i < PhysAddrLen; ++i)
        {
            str[i] = MacAddr[i].ToString("x2");
        }
        return String::Join(":", str);
    }
};

注意：

• 我们不需要new 或delete 某个其他类，因为这只是一个函数调用。这也是为什么我做了函数static，所以我们不需要在vb.net中new这个。
• 我已经制作了参数和返回值字符串（基于 C++ 示例和 p/invoke 示例的用法）
• 我跳过代码来测试错误。在这种情况下，您可能会抛出异常。
• 我建议使用public enum class 并分配值，而不是使用单独的static const ULONG。

由于我对这个函数或它的使用不太了解，所以我没有测试过这段代码，但它至少应该为你指明了正确的方向。