Is there a faster alternative to enumerating folde

问题:

I need to get all paths to subfolders within a folder (with WinAPIs and C++.) So far the only solution that I found is recursively calling FindFirstFile / FindNextFile but it takes a significant amount of time to do this on a folder with a deeper hierarchy.

So I was wondering, just to get folder names, is there a faster approach?

回答1:

If you really just need subfolders you should be able to use FindFirstFileEx with search options to filter out non-directories.

The docs suggest this is an advisory flag only, but your filesystem may support this optimization - give it a try.

FindExSearchLimitToDirectories

This is an advisory flag. If the file system supports directory filtering, the function searches for a file that matches the specified name and is also a directory. If the file system does not support directory filtering, this flag is silently ignored.

回答2:

That is the fastest approach you can come across. Also you may consider using another thread to manage directory enumerations as it takes a lot of time. even Microsoft file explorer spend some time if the directory has a lot of sub folders/files.

One more thing here is that you can enumerate directories once and then register for any updates. so the cost of enumerating the folder should be made only once during start up.

回答3:

A faster approach would be to bypass the FindFirstFile...() API and go straight to the file system directly. You can use DeviceIoControl() with the FSCTL_ENUM_USN_DATA control to access the master file table, at least on NTFS formatted volumes. With that information, you can directly access the records for files/folders, which includes their attributes, parent info, etc. Yes, it would be more work, but it should also be faster since you can optimize the code to access just the pieces you need.