windows 如何在完成例程中使用 ReadDirectoryChangesW() 方法？
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How to use ReadDirectoryChangesW() method with completion routine?
提问by user26404
I want to use function ReadDirectoryChangesW()in asynchronous mode with I/O completion routine supplied.
我想ReadDirectoryChangesW()在提供 I/O 完成例程的异步模式下使用函数。
The question is I don't know how to retrieve the exact information about the change in the completion routine (a CALLBACKfunction). Completion routine is defined like this:
问题是我不知道如何检索有关完成例程（一个CALLBACK函数）更改的确切信息。完成例程定义如下：
VOID CALLBACK FileIOCompletionRoutine(
[in] DWORD dwErrorCode,
[in] DWORD dwNumberOfBytesTransfered,
[in] LPOVERLAPPED lpOverlapped
);
I wonder the information is included in the LPOVERLAPPEDstructure. But I don't know how to get it.
我想知道信息是否包含在LPOVERLAPPED结构中。但我不知道如何得到它。
回答by Andrew
Excellent question! It's 7 years late, but here's somewhat of an answer, or, more importantly, how to find it. So, the documentation for ReadDirectoryChangesW:
好问题！晚了 7 年，但这里有一些答案，或者更重要的是，如何找到它。因此，ReadDirectoryChangesW 的文档：
https://msdn.microsoft.com/en-us/library/windows/desktop/aa365465%28v=vs.85%29.aspx
https://msdn.microsoft.com/en-us/library/windows/desktop/aa365465%28v=vs.85%29.aspx
in the Parameters section gives a link to FileIOCompletionRoutine:
在参数部分中提供了指向 FileIOCompletionRoutine 的链接：
https://msdn.microsoft.com/en-us/library/windows/desktop/aa364052%28v=vs.85%29.aspx
https://msdn.microsoft.com/en-us/library/windows/desktop/aa364052%28v=vs.85%29.aspx
which in the Examples section gives a link to Named Pipe Server Using Completion Routines:
在示例部分提供了使用完成例程的命名管道服务器的链接：
https://msdn.microsoft.com/en-us/library/windows/desktop/aa365601%28v=vs.85%29.aspx
https://msdn.microsoft.com/en-us/library/windows/desktop/aa365601%28v=vs.85%29.aspx
which believe it or not doesn't even use ReadDirectoryChangesW but actually gives an example using ReadFileEx, which alsouses FileIOCompletionRoutine:
信不信由你甚至不使用 ReadDirectoryChangesW 但实际上给出了一个使用 ReadFileEx 的例子，它也使用 FileIOCompletionRoutine：
https://msdn.microsoft.com/en-us/library/windows/desktop/aa365468%28v=vs.85%29.aspx
https://msdn.microsoft.com/en-us/library/windows/desktop/aa365468%28v=vs.85%29.aspx
and you can see an example of them using these two functions (ReadFileEx and CompletedReadRoutine (which is an implementation of the application-defined callback function FileIOCompletionRoutine)) in this piece of code:
您可以在这段代码中看到使用这两个函数（ReadFileEx 和 CompletedReadRoutine（这是应用程序定义的回调函数 FileIOCompletionRoutine 的实现））的示例：
// CompletedWriteRoutine(DWORD, DWORD, LPOVERLAPPED)
// This routine is called as a completion routine after writing to
// the pipe, or when a new client has connected to a pipe instance.
// It starts another read operation.
VOID WINAPI CompletedWriteRoutine(DWORD dwErr, DWORD cbWritten,
LPOVERLAPPED lpOverLap)
{
LPPIPEINST lpPipeInst;
BOOL fRead = FALSE;
// lpOverlap points to storage for this instance.
lpPipeInst = (LPPIPEINST) lpOverLap;
// The write operation has finished, so read the next request (if
// there is no error).
if ((dwErr == 0) && (cbWritten == lpPipeInst->cbToWrite))
fRead = ReadFileEx(
lpPipeInst->hPipeInst,
lpPipeInst->chRequest,
BUFSIZE*sizeof(TCHAR),
(LPOVERLAPPED) lpPipeInst,
(LPOVERLAPPED_COMPLETION_ROUTINE) CompletedReadRoutine);
// Disconnect if an error occurred.
if (! fRead)
DisconnectAndClose(lpPipeInst);
}
// CompletedReadRoutine(DWORD, DWORD, LPOVERLAPPED)
// This routine is called as an I/O completion routine after reading
// a request from the client. It gets data and writes it to the pipe.
VOID WINAPI CompletedReadRoutine(DWORD dwErr, DWORD cbBytesRead,
LPOVERLAPPED lpOverLap)
{
LPPIPEINST lpPipeInst;
BOOL fWrite = FALSE;
// lpOverlap points to storage for this instance.
lpPipeInst = (LPPIPEINST) lpOverLap;
// The read operation has finished, so write a response (if no
// error occurred).
if ((dwErr == 0) && (cbBytesRead != 0))
{
GetAnswerToRequest(lpPipeInst);
fWrite = WriteFileEx(
lpPipeInst->hPipeInst,
lpPipeInst->chReply,
lpPipeInst->cbToWrite,
(LPOVERLAPPED) lpPipeInst,
(LPOVERLAPPED_COMPLETION_ROUTINE) CompletedWriteRoutine);
}
// Disconnect if an error occurred.
if (! fWrite)
DisconnectAndClose(lpPipeInst);
}
It's not a great answer (I was only exploring whether I even wanted to use these functions, myself), but it should help people get started.
这不是一个很好的答案（我只是在探索我自己是否想使用这些功能），但它应该可以帮助人们开始。
See also:
也可以看看：
https://msdn.microsoft.com/en-us/library/windows/desktop/aa365261%28v=vs.85%29.aspx
https://msdn.microsoft.com/en-us/library/windows/desktop/aa365261%28v=vs.85%29.aspx
