c# - 从非托管代码回调到托管代码

Question

我正在触发我的托管代码并启动对非托管代码的调用。非托管代码中有一个回调。从非托管我在我的托管方法“DelegateMethod”中获得回调。但是我没有从非托管代码中获得正确的参数/参数值。请帮我解决这个问题

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace TestApp
{
    public class Program
    {
        public delegate void fPointer(byte[] Sendapdu, ref int Sendlen, byte[] Recvapdu, ref int Recvlen);

        public struct sCommsAbstraction
        {
            ///Function to send and receive.
            public fPointer pf_TxRx;

            ///Other functions if necessary, e.g. reset
        }

        // Create a method for a delegate. 
        public static void DelegateMethod(byte[] Sendapdu, ref int Sendlen, byte[] Recvapdu, ref int Recvlen)
        {
            //This is called from unmanaged code. I am not getting proper arguments
            Console.WriteLine(Sendlen);
        }

        [DllImport("AuthLibrary.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern int CmdLib_RegisterItsIO(ref sCommsAbstraction psCommsFunctions);

        [DllImport("AuthLibrary.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern int CmdLib_OpenApplication();

        [DllImport("TransparentChannel.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern int TC_Transceive(byte[] writeBuf, ref int writeBufLen, byte[] readBuf, ref int pwReadBufferLen);

        static void Main(string[] args)
        {
            sCommsAbstraction psCommsFunctions = new sCommsAbstraction();
            // Instantiate the delegate.
            psCommsFunctions.pf_TxRx = DelegateMethod;

            CmdLib_RegisterItsIO(ref psCommsFunctions);
            CmdLib_OpenApplication();
        }
    }
}

我未管理的代码片段在这里 - CmdLib.c

//C code - unmanaged

typedef int32_t (*pFTransceive)(const uint8_t *prgbWriteBuffer, const uint16_t *pwWriteBufferLen, uint8_t *prgbReadBuffer, uint16_t *pwReadBufferLen);

typedef struct sCommsAbstraction
{
    ///Function to send and receive.
    pFTransceive pf_TxRx;

    ///Other functions if necessary, e.g. reset
}sCommsAbstraction_d

static sCommsAbstraction_d sCommsAbstraction = {0};

void CmdLib_RegisterItsIO(const sCommsAbstraction_d *psCommsFunctions)
{
    sCommsAbstraction.pf_TxRx = psCommsFunctions->pf_TxRx;    
}
void CmdLib_OpenApplication()
{
    sCommsAbstraction.pf_TxRx(rgbAPDUBuffer,&wTotalLength,rgbAPDUBuffer,&psApduData->wResponseLength);
}

Answer 1

您的委托(delegate)声明与 pFTransceive 函数指针声明不匹配。这会在您的回调方法中产生垃圾参数值。

靠近:

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public delegate void fPointer(
        [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)]
        byte[] Sendapdu, ref short Sendlen,
        [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)]
        byte[] Recvapdu, ref short Recvlen
    );

请注意 required 属性以匹配 C/C++ 程序中使用的默认调用约定。以及匹配 uint16_t 的short 参数类型。`

更多关于调用约定的奥秘在this post .

---

    sCommsAbstraction psCommsFunctions = new sCommsAbstraction();

这是您必须担心的另一件事。只要 native 代码可以进行回调，该对象就需要生存。现在它没有，下一次垃圾收集将销毁它，因为垃圾收集器无法发现 native 代码正在使用它。 Kaboom 当 native 代码进行回调时。您还没有看到该错误，调试器现在使对象保持事件状态。这不会在生产中发生。

正如所写，您需要将此语句添加到 Main() 方法的底部:

    GC.KeepAlive(psCommsFunctions);

将它存储在 static 变量中是更好的方法，只有当您知道 native 代码不会这样做时才将其设置回 null不再进行回调。