C# 调用C++DLL传递指向指针的指针参数的方法

struct DeviceInfo
{
char szDeviceName[DEVICE_NAME_LEN];
char szMACAddress[MAC_ADDRESS_LEN];
char szDeviceIP[DEVICE_IP_LEN];
};

[StructLayout(LayoutKind.Sequential)]
public struct DeviceInfo
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]
public string szDeviceName;

[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 13)]
public string szMACAddress;

[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 17)]
public string szDeviceIP;

}

情况1：C++的dll负责分配内存

#define DLL_API  extern "C"  __declspec(dllexport)
DLL_API int findAllDevices(DeviceInfo** ppDeviceInfoList,int * pCount);

[DllImport("IPAlter_d.dll")]
public extern static int findAllDevices(out IntPtr pDeviceInfo, ref int pCount);

IntPtr pBuff = new IntPtr();//直接new一个参数即可

if (IPAlter.findAllDevices(out pBuff, ref cout) != 1)
{
System.Console.WriteLine("搜索失败！");
System.Console.ReadLine();
return;
}

for (int i = 0; i < cout; i++)
{

IntPtr pPonitor = new IntPtr(pBuff.ToInt64() + Marshal.SizeOf(typeof(DeviceInfo)) * i);

System.Console.WriteLine(((DeviceInfo)Marshal.PtrToStructure(pPonitor, typeof(DeviceInfo))).szDeviceName);
System.Console.WriteLine(((DeviceInfo)Marshal.PtrToStructure(pPonitor, typeof(DeviceInfo))).szDeviceIP);
System.Console.WriteLine(((DeviceInfo)Marshal.PtrToStructure(pPonitor, typeof(DeviceInfo))).szMACAddress);
}

情况2：C#负责分配内存

DLL_API int findAllDevice(DeviceInfo* ppDeviceInfoList,int * pCount);

[DllImport("IPAlter_d.dll")]
public extern static int findAllDevice(IntPtr pDeviceInfo, ref int pCount);

DeviceInfo[] DeviceInfoList = new DeviceInfo[50];
int size = Marshal.SizeOf(typeof(DeviceInfo)) * 50;
byte[] bytes = new byte[size];
IntPtr pBuff = Marshal.AllocHGlobal(size);

if (IPAlter.findAllDevice(pBuff, ref cout) != 1)
{
System.Console.WriteLine("搜索失败！");
System.Console.ReadLine();
return;
}

for (int i = 0; i < cout; i++)
{

IntPtr pPonitor = new IntPtr(pBuff.ToInt64() + Marshal.SizeOf(typeof(DeviceInfo)) * i);
DeviceInfoList[i] = (DeviceInfo)Marshal.PtrToStructure(pPonitor, typeof(DeviceInfo));

System.Console.WriteLine(DeviceInfoList[i].szDeviceName);
System.Console.WriteLine(DeviceInfoList[i].szDeviceIP);
System.Console.WriteLine(DeviceInfoList[i].szMACAddress);
}
Marshal.FreeHGlobal(pBuff);