cwindowswinapintfs

How to get "valid data length" of a file?

There is a function to set the "valid data length" value: SetFileValidData, but I didn't find a way to get the "valid data length" value.

I want to know about given file if the EOF is different from the VDL, because writing after the VDL in case of VDL<EOF will cause a performance penalty as described here.

Solution

  • I found this page, claims that:

    there is no mechanism to query the value of the VDL

    So the answer is "you can't".

    If you care about performance you can set the VDL to the EOF, but then note that you may allow access old garbage on your disk - the part between those two pointers, that supposed to be zeros if you would access that file without setting the VDL to point the EOF.