blocks|key|496646|text|据我所知，在关闭的文件上没有用户模式的通知API。您提出的循环可能真的是最好的方法。你唯一能做的就是在一个过滤器驱动程序和进程监视器中观察CloseFile，但是讨厌……|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|496647|entityMap^0|1X|9|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

There's no user-mode API for notifications on a closed file that I'm aware of. The loop you've proposed is really probably the best way. The only other thing you could do would be to watch for <code>CloseFile</code> in a filter driver ala Process Monitor, but yuck...

blocks|key|514623|text|如果您对文件是如何创建的有所了解，可以等到文件停止增长X秒，或者等到一个前哨文件被删除。或者感知创建它们的程序的状态。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|514624|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

If you know something about how the file is created, maybe wait until the file stops growing for X seconds, or wait until a sentinel file is deleted. Or sense the state of the program which creates them.

blocks|key|1903863|text|我不认为对于您正在寻找的事件类型有通知，但作为一种改进，我建议逐步延迟。通过这种方式，您将获得更快的响应时间，例如拖放，并且如果用户在Excel中保持文件打开一个小时，则不会占用CPU。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1903864|int+delay=+10;
while+((hFile+=+CreateFile+(path,+GENERIC_READ,+FILE_SHARE_READ,+NULL,+OPEN_EXISTING,+0,+NULL))+==+INVALID_HANDLE_VALUE)
{
++++if+(GetLastError()+==+ERROR_SHARING_VIOLATION)+{
++++++++Sleep+(delay);
++++++++if+(delay<5120)+//+max+delay+approx+5.Sec
++++++++++++delay*=+2;
++++}
++++else
++++++++break;+//+some+other+error+occurred
}|code-block|syntax|javascript|1903865|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I don't think there is a notification for the kind of event you're looking for, but as an improvement, I'd suggest progressive delays. This way you will get fast response times for stuff like a drag/drop and won't hog the CPU with a tight loop if the user keeps the file open for an hour in Excel.

<pre><code>int delay= 10;
while ((hFile = CreateFile (path, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, NULL)) == INVALID_HANDLE_VALUE)
{
 if (GetLastError() == ERROR_SHARING_VIOLATION) {
 Sleep (delay);
 if (delay&lt;5120) // max delay approx 5.Sec
 delay*= 2;
 }
 else
 break; // some other error occurred
}
</code></pre>

blocks|key|514980|text|正如@Matt+Davis所说，不幸的是，没有用户模式API，但有一个解决方案，这取决于你的用例(我在下面写了我的用例)可能会做你想要的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|514981|过去，我的工作是在调用ReadDirectoryChangesW时注册FILE_NOTIFY_CHANGE_LAST_WRITE+，而不是+FILE_NOTIFY_CHANGE_FILE_NAME|offset|length|style|CODE|BOLD|514982|ZeroMemory(&overlapped,+sizeof(OVERLAPPED));
overlapped.hEvent+=+hChangeEvent;

//+...++++
ReadDirectoryChangesW(hSpoolPath,
++++++++++++++++++++++eventBuffer,
++++++++++++++++++++++EVENT_BUF_LENGTH,
++++++++++++++++++++++FALSE,
++++++++++++++++++++++FILE_NOTIFY_CHANGE_LAST_WRITE,+//+<----
++++++++++++++++++++++NULL,
++++++++++++++++++++++&overlapped,
++++++++++++++++++++++NULL);
//+...
HANDLE+events[2];

events[0]+=+hChangeEvent;
events[1]+=+hCancelEvent;

DWORD+wRc+=+WaitForMultipleObjects(2,+events,+FALSE,+DIRECTORY_WATCH_TIMEOUT);|code-block|syntax|javascript|514983|在创建文件并向其写入之后，一旦拥有进程关闭句柄，最后一次写入时间就会更新。|514984|我的用例是这样一个进程，它通过TCP/IP接收HTTP请求，并将HTTP主体写入到一个目录中，在这个目录中，另一个进程在接收进程完成对它的写入(并关闭句柄)后立即获取它。http-server是唯一写入该目录的进程，因此我可以依赖create-write-close模式。|514985|entityMap^0|0|B|L|Z|T|1Y|S|1T|4|0|0|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|U|8|@$D|V|E|W|F|G]|$D|X|E|Y|F|G]|$D|Z|E|10|F|G]|$D|11|E|12|F|H]]|9|@]|A|$]]|$1|I|3|J|5|K|7|13|8|@]|9|@]|A|$L|M]]|$1|N|3|O|5|6|7|14|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|15|8|@]|9|@]|A|$]]|$1|R|3|-4|5|6|7|16|8|@]|9|@]|A|$]]]|S|$]]

As @Matt Davis said, there is unfortunately no user-mode API but there is a workaround that depending on your use-case (I've written mine below) may do just what you want.

What worked for me in the past was registering for <code>FILE_NOTIFY_CHANGE_LAST_WRITE</code> instead of <code>FILE_NOTIFY_CHANGE_FILE_NAME</code> when calling <code>ReadDirectoryChangesW</code>:

<pre><code>ZeroMemory(&amp;overlapped, sizeof(OVERLAPPED));
overlapped.hEvent = hChangeEvent;

// ... 
ReadDirectoryChangesW(hSpoolPath,
 eventBuffer,
 EVENT_BUF_LENGTH,
 FALSE,
 FILE_NOTIFY_CHANGE_LAST_WRITE, // &lt;----
 NULL,
 &amp;overlapped,
 NULL);
// ...
HANDLE events[2];

events[0] = hChangeEvent;
events[1] = hCancelEvent;

DWORD wRc = WaitForMultipleObjects(2, events, FALSE, DIRECTORY_WATCH_TIMEOUT);
</code></pre>

The last write time gets updated as soon as the owning process closes the handle after creating the file and writing to it.

My use-case was one process that received HTTP-requests via TCP/IP and wrote the HTTP-body into a directory, where another process picked it up as soon as the receiving process was finished writing (and consequently closing the handle) it. The http-server was the only process that wrote to that directory, so I could rely on the create-write-close pattern.

I'm watching a directory by calling <code>ReadDirectoryChangesW</code> synchronously. When a new file is available, I try to access it immediately with <code>CreateFile</code> with <code>GENERIC_READ</code> and <code>FILE_SHARE_READ</code>, but this gives me <code>ERROR_SHARING_VIOLATION</code>. The process that put the file in the watched directory does not finish writing by the time I try to read it.

Is there any way to reliably wait until the file is available for reading? I can put the method into a loop like the one below, but I'm hoping there's a better way.

<pre><code>while ((hFile = CreateFile (path, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, NULL)) == INVALID_HANDLE_VALUE)
{
 if (GetLastError() == ERROR_SHARING_VIOLATION)
 Sleep (500);
 else
 break; // some other error occurred
}

if (hFile == INVALID_HANDLE_VALUE)
{
 // deal with other error
 return 0;
}

ReadFile (...);
</code></pre>

Waiting until a file is available for reading with Win32

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在通过同步调用ReadDirectoryChangesW来查看目录。当有新文件可用时，我会尝试用CreateFile、GENERIC_READ和FILE_SHARE_READ立即访问它，但这会给我ERROR_SHARING_VIOLATION。在我尝试读取该文件时，将该文件放入监视目录的进程尚未完成写入。有没有办法...

问等待文件可用于使用Win32读取
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