Re: Implementing stat() with FindFirstFile()

From: Johannes Sixt <j6t@kdbg.org>
Date: Mar 21, 2009, 19:55 UTC
Message-ID: <200903212055.15026.j6t@kdbg.org>
In-Reply-To: <20090321154738.GA27249@jeeves.jpl.local>

On Samstag, 21. März 2009, Magnus Bäck wrote:

> Is there any reason why compat/win32.h uses GetFileAttributesEx()
> instead of FindFirstFile() to implement the stat() call on Windows?
> The current implementation requires each queried file to be opened
> and closed while FindFirstFile() only reads the directory.

There is: File times are extremely important for git. Unfortunately, MS's implementation of stat and utime are broken, and they do use FindFirstFile(). Read up on the topic here:

http://search.cpan.org/~shay/Win32-UTCFileTime-1.50/lib/Win32/UTCFileTime.pm

To quote the important sentence:

"The problem with Microsoft's stat(2) and utime(2) [...] is basically this: file times reported by stat(2) or stored by utime(2) may change by an hour as we move into or out of daylight saving time (DST) if the computer is set to "Automatically adjust clock for daylight saving changes" [...]."

Be sure to read section "Background Reference".

Besides that, our stat() implementation is already ca. twice as fast as MSVCRT's stat(). (Thank you, Marius!)

-- Hannes