使用PInvoke在.NET中进行WinUSB异步调用

我用USB编程了一个微控制器，并用WinUSB将它连接到一台PC上。我能用C++和VB.NET与UCL通信，使用同步（阻塞，重叠=空）调用。我刚在C++中得到异步调用，但我不知道如何在.NET中编码它，还有一个问题我不确定：

问题1： 在C++中，我最初尝试使用IO完成回调对象进行异步调用，但是当我调用WiUSB读取它时，返回了一个错误，即异步IO已经在文件句柄（句柄Hoice）上进行了，CreateThreadpoolIo不会接受WiUSB句柄（pWuSubIInFruteHead HWiuSb句柄）。我猜WinUSB使用这个文件句柄作为IO，所以我不能。我最终使用Wait回调对象实现了它。它现在正在工作，我只是想澄清一下，我所做的是正确的用法

我有点困惑的是CreateThreadpoolWait调用。起初我以为这是在创建一个线程池，就像MSDN中的其他示例一样，但现在我认为它只是一个在默认线程池上运行的对象。此外，objConext是用于将调用与其回调同步的变量，即回调指向objConext的PVOID上下文

以下是c代码片段：

// Receive data asynchronously
void BeginReceiveData(UCHAR bytPipeId, UCHAR *bytData, ULONG intLength, PTP_WAIT_CALLBACK cbCallback)
{
    // Create the event
    HANDLE hEventCallback = CreateEvent(NULL, FALSE, FALSE, NULL);

    // Check for an error
    if (!hEventCallback)
    {
        // Set the error
        printf(strError, "Error creating callback event: %d.", GetLastError());
    }

    // Create the thread pool wait object
    tpWait = CreateThreadpoolWait(cbCallback, &objConext, NULL);

    // Check for an error
    if (!tpWait)
    {
        // Set the error
        printf(strError, "Error creating thread pool: %d.", GetLastError());
    }

    // Place the wait object in the thread pool
    SetThreadpoolWait(tpWait, hEventCallback, NULL);

    // Clear the callback
    ZeroMemory(&oCallback, sizeof(oCallback));

    // Set the event
    oCallback.hEvent = hEventCallback;

    // Read
    BOOL bResult = WinUsb_ReadPipe(*hWinUsbHandle, bytPipeId, bytData, intLength, NULL, &oCallback);

    // Check for an error
    if (!bResult)
    {
        if (GetLastError() != ERROR_IO_PENDING)
        {
            // Set the error
            printf(strError, "Error reading pipe: %d.", GetLastError());
        }
    }
}

// Receive data callback
void CALLBACK UsbCallback(PTP_CALLBACK_INSTANCE Instance, PVOID Context, PTP_WAIT Wait, TP_WAIT_RESULT WaitResult)
{
}

问题2： 如何将上述内容转换为.NET？这是我目前的猜测：

    Dim wait As New WaitCallback(AddressOf UsbCallback)

    ' Create the event
    Dim eEventCallback As New AutoResetEvent(False)

    ThreadPool.QueueUserWorkItem(wait, Nothing)

    Dim oCallback As New Overlapped(0, 0, eEventCallback.SafeWaitHandle.DangerousGetHandle, Nothing)

    'Dim oCallback As New NativeOverlapped

    oCallback.EventHandleIntPtr = eEventCallback.SafeWaitHandle.DangerousGetHandle

    ' Read
    Dim bResult As Boolean = WinUsb_ReadPipe(hWinUsbHandle, bytPipeId, bytData, intLength, intLength, oCallback.EventHandleIntPtr)

<DllImport("winusb.dll", SetLastError:=True, CharSet:=CharSet.Auto)>
        Public Function WinUsb_ReadPipe(InterfaceHandle As IntPtr, PipeID As Byte, Buffer() As Byte, BufferLength As UInteger, ByRef LengthTransferred As UInteger, Overlapped As IntPtr) As Boolean
        End Function

虽然我还没有真正找到问题1的答案：这是否是一种“正确”的方法，但它似乎表现得相当好。以下是主要代码片段：

' Receive data asynchronously
    Private Sub BeginReceiveData(bytPipeId As Byte, bytData() As Byte, intLength As UInteger)
        ' Allocate memory for the callback
        ptrContext = Marshal.AllocHGlobal(Marshal.SizeOf(GetType(TestContext)))

        ' Copy the structure to memory
        Marshal.StructureToPtr(objConext, ptrContext, True)


        ' Create the callback
        cbCallback = New UsbCallbackDelegate(AddressOf UsbCallback)


        ' Create the event
        Dim areEvent As New AutoResetEvent(False)

        ' Set the event
        hEventCallback = areEvent.SafeWaitHandle.DangerousGetHandle

        ' Create the thread pool wait object
        tpWait = CreateThreadpoolWait(Marshal.GetFunctionPointerForDelegate(cbCallback), ptrContext, IntPtr.Zero)

        ' Place the wait object in the thread pool
        SetThreadpoolWait(tpWait, hEventCallback, IntPtr.Zero)

        ' Set the event
        oCallback.EventHandle = hEventCallback

        ' Read
        Dim bResult As Boolean = WinUsb_ReadPipe(hWinUsbHandle, bytPipeId, bytData, intLength, intLength, oCallback)

        If Not bResult Then
            If Not Marshal.GetLastWin32Error = 997 Then
                ' Get the error
                Dim intError As Integer = Marshal.GetLastWin32Error

                Throw New Win32Exception(intError, "Error getting device information.")
            End If
        End If
    End Sub

    ' Delegate for USB callbacks
    Private Delegate Sub UsbCallbackDelegate(Instance As IntPtr, Context As IntPtr, Wait As IntPtr, WaitResult As UInteger)

    ' Callback
    Private Sub UsbCallback(Instance As IntPtr, Context As IntPtr, Wait As IntPtr, WaitResult As UInteger)
        ' Number of bytes transferred
        Dim intTransferred As UInteger

        ' Get the number of bytes transferred
        WinUsb_GetOverlappedResult(hWinUsbHandle, oCallback, intTransferred, False)

        ' Get the context from memory
        Dim objConext As TestContext = Marshal.PtrToStructure(Context, GetType(TestContext))

        ' Free the memory
        Marshal.FreeHGlobal(Context)


        ' Do some work on the data


End Sub

主API DLL导入

<DllImport("winusb.dll", SetLastError:=True, CharSet:=CharSet.Auto)>
        Public Function WinUsb_GetOverlappedResult(InterfaceHandle As IntPtr, ByRef lpOverlapped As Threading.NativeOverlapped, ByRef lpNumberOfBytesTransferred As UInteger, bWait As Boolean) As IntPtr
        End Function

        <DllImport("kernel32.dll", SetLastError:=True, CharSet:=CharSet.Auto)>
        Public Function CreateThreadpoolWait(pfnwa As IntPtr, pv As IntPtr, pcbe As IntPtr) As IntPtr
        End Function

        <DllImport("kernel32.dll", SetLastError:=True, CharSet:=CharSet.Auto)>
        Public Function SetThreadpoolWait(pwa As IntPtr, h As IntPtr, pftTimeout As IntPtr) As IntPtr
        End Function

        <DllImport("kernel32.dll", SetLastError:=True, CharSet:=CharSet.Auto)>
        Public Function CloseThreadpoolWait(pwa As IntPtr) As IntPtr
        End Function

警告：这里没有很多清理代码，请查看MSDN中的c代码，了解如何正确执行此操作。我认为一个面向对象的方法可能是最好的保持句柄的活动性，并实现IDIsposable，以便在完成时进行清理

有人对开源DLL感兴趣吗P

<DllImport("winusb.dll", SetLastError:=True, CharSet:=CharSet.Auto)>
        Public Function WinUsb_GetOverlappedResult(InterfaceHandle As IntPtr, ByRef lpOverlapped As Threading.NativeOverlapped, ByRef lpNumberOfBytesTransferred As UInteger, bWait As Boolean) As IntPtr
        End Function

        <DllImport("kernel32.dll", SetLastError:=True, CharSet:=CharSet.Auto)>
        Public Function CreateThreadpoolWait(pfnwa As IntPtr, pv As IntPtr, pcbe As IntPtr) As IntPtr
        End Function

        <DllImport("kernel32.dll", SetLastError:=True, CharSet:=CharSet.Auto)>
        Public Function SetThreadpoolWait(pwa As IntPtr, h As IntPtr, pftTimeout As IntPtr) As IntPtr
        End Function

        <DllImport("kernel32.dll", SetLastError:=True, CharSet:=CharSet.Auto)>
        Public Function CloseThreadpoolWait(pwa As IntPtr) As IntPtr
        End Function

' Receive data asynchronously on endpoint 1
    BeginReceiveData(129, bytData, 8)

    While True
    ' Garbage collection
        GC.Collect()
        GC.WaitForFullGCComplete()
    End While


    ' Callback
    Private Sub UsbCallback(Instance As IntPtr, Context As IntPtr, Wait As IntPtr, WaitResult As UInteger)
        ' ...
        ' Once data is received, receive more
        BeginReceiveData(129, bytData, 8)
        '...
    End Sub