pInvoke readFile():重叠的I/O操作正在进行中

问题描述

我正在尝试开发一种与电子卡通信的功能.我需要使用readFile()函数:

I'm trying to develop a function to communicate with an electronic card. I need to use the readFile() function :

[DllImport("kernel32.dll", SetLastError = true)]
static extern bool ReadFile(IntPtr hFile, ref byte lpBuffer,
       uint nNumberOfBytesToRead, out uint lpNumberOfBytesRead, Overlapped lpOverlapped);

我的功能是:

EventObject = CreateEvent(IntPtr.Zero,true,true,"");
lastError = Marshal.GetLastWin32Error();

HIDOverlapped = new System.Threading.Overlapped();
HIDOverlapped.OffsetLow = 0;
HIDOverlapped.OffsetHigh = 0;
HIDOverlapped.EventHandleIntPtr = EventObject;

readHandle = CreateFile(MyDeviceInterfaceDetailData.DevicePath, (GENERIC_READ | GENERIC_WRITE), (FILE_SHARE_READ | FILE_SHARE_WRITE), IntPtr.Zero, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, IntPtr.Zero);

 uint numberOfBytesRead;
        readBuffer= new byte[8];
        string byteValue;


 bool result = ReadFile(readHandle, ref readBuffer[0], (uint)capabilities.InputReportByteLength, out numberOfBytesRead, HIDOverlapped);
 lastError = Marshal.GetLastWin32Error(); //Problem

最后一行中的函数Marshal.GetLastWin32Error()返回错误代码997.

The function Marshal.GetLastWin32Error() in the last line returns error code 997.

在第二段中，出现另一个错误，代码为0xc0000005(FatalExecutionEngineError)，并且软件崩溃.

In the sencond passage, an other error appears with the code 0xc0000005 (FatalExecutionEngineError) and the software crash.

您知道我可以尝试什么吗?

Have you got an idea of what I can tried?

推荐答案

这不是问题.

错误代码997是ERROR_IO_PENDING，这是ReadFile在开始重叠读取时将返回的内容.

Error code 997 is ERROR_IO_PENDING, which is what ReadFile will return upon starting an overlapped read.

从文档:

备注:

使用重叠的I/O是一项要求吗?

Is using overlapped I/O a requirement?

使用此函数定义:

[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
public static extern SafeFileHandle CreateFile(string lpFileName, uint dwDesiredAccess, uint dwShareMode, IntPtr lpSecurityAttributes, uint dwCreationDisposition, uint dwFlagsAndAttributes, IntPtr hTemplateFile);

您可以从使用Win API打开的文件中创建常规的FileStream:

You can create regular FileStreams from a file opened with the Win API:

var fileHandle = CreateFile(.....);

if (fileHandle.IsInvalid)
    Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error());

// The last parameter of the FileStream constructor (isAsync) will make the class use async I/O
using (var stream = new FileStream(fileHandle, FileAccess.ReadWrite, 4096, true))
{
    var buffer = new byte[4096];

    // Asynchronously read 4kb
    var bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length);
}

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