关于多个应用程序打开同一文件的问题

[BigDoll7973]

FEAT1 同一A文件同时被多个应用程序打开时，提供同步
1.1 允许多个应用程序同时打开一个A文件
1.2 在多个应用程序同时打开一个A文件时，保持他们的同步.在一个应用程序存入后,在另一应用程序激活时,将提示用户A文件已经被修改，并重新载入和刷新．

说明：这个A文件是自定义的格式文件。如果我写一个B.dll，有App1应用程序调用B.dll打开A文件，App2应用程序调用另一个B.dll打开A文件（B.dll虽然是相同代码，但相当于两一个B.dll的拷贝），那么如果App1通过B.dll对A进行了修改，App2又如何可以同步的知道呢？

我曾经想用共享内存的方法，但不知道该如何起步。

[fireseed]

Platform SDK: File Storage
Monitoring Changes in a Directory or Directory Tree
The following example monitors the directory tree starting at C:\ for directory name changes. It also monitors the C:\WINDOWS directory for file name changes.

The example uses the FindFirstChangeNotification function to create two notification handles and the WaitForMultipleObjects function to wait on the handles. Whenever a directory is created or deleted in the tree starting at C:\ , the example updates the entire directory tree. Whenever a file is created or deleted in the C:\WINDOWS directory, the example refreshes the WINDOWS directory. The FindNextChangeNotification function restarts the change notification each time the example processes a change.

DWORD dwWaitStatus;
HANDLE dwChangeHandles[2];

// Watch the C:\WINDOWS directory for file creation and
// deletion.

dwChangeHandles[0] = FindFirstChangeNotification(
"C:\\WINDOWS", // directory to watch
FALSE, // do not watch the subtree
FILE_NOTIFY_CHANGE_FILE_NAME); // watch file name changes

if (dwChangeHandles[0] == INVALID_HANDLE_VALUE)
ExitProcess(GetLastError());

// Watch the C:\ subtree for directory creation and
// deletion.

dwChangeHandles[1] = FindFirstChangeNotification(
"C:\\", // directory to watch
TRUE, // watch the subtree
FILE_NOTIFY_CHANGE_DIR_NAME); // watch dir. name changes

if (dwChangeHandles[1] == INVALID_HANDLE_VALUE)
ExitProcess(GetLastError());

// Change notification is set. Now wait on both notification
// handles and refresh accordingly.

while (TRUE)
{

// Wait for notification.

dwWaitStatus = WaitForMultipleObjects(2, dwChangeHandles,
FALSE, INFINITE);

switch (dwWaitStatus)
{
case WAIT_OBJECT_0:

// A file was created or deleted in C:\WINDOWS.
// Refresh this directory and restart the
// change notification. RefreshDirectory is an
// application-defined function.

RefreshDirectory("C:\\WINDOWS")
if ( FindNextChangeNotification(
dwChangeHandles[0]) == FALSE )
ExitProcess(GetLastError());
break;

case WAIT_OBJECT_0 + 1:

// A directory was created or deleted in C:\.
// Refresh the directory tree and restart the
// change notification. RefreshTree is an
// application-defined function.

RefreshTree("C:\\");
if (FindNextChangeNotification(
dwChangeHandles[1]) == FALSE)
ExitProcess(GetLastError());
break;

default:
ExitProcess(GetLastError());
}
}
Platform SDK Release: August 2001 What did you think of this topic?
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(U.S/Canada) (International)

[programmer200x]

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[BigDoll7973]

用这样的方法的的话目录一多，很占CPU的，所以如果让他监视一个硬盘的话，肯定是要死机了