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Date:	Mon, 31 Jan 2005 09:05:13 -0600
From:	Brian Ford <ford AT vss DOT fsi DOT com>
Reply-To:	cygwin AT cygwin DOT com
To:	Dan Ch <force296-cygwin AT yahoo DOT com>
cc:	cygwin AT cygwin DOT com
Subject:	Re: Why does cygwin1.dll use NtCreateFile() instead of CreateFile()
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X-OriginalArrivalTime:	31 Jan 2005 15:04:57.0420 (UTC) FILETIME=[3A4FC8C0:01C507A6]
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On Sun, 30 Jan 2005, Dan Ch wrote:

> I noticed that cygwin-1.5.12-1/winsup/cygwin/fhandler.cc
> uses NtCreateFile() instead of CreateFile() on Windows NT based
> operating systems (NT, 2000, 2003, XP) for opening files.  Why?  I
> checked the archives for this mailing list and noted some activity
> that discuses some side affects caused by using NtCreateFile()
> instead of CreateFile() such as being able to use file names that are
> off limits to normal Windows applications.  But I could not find
> anything that explains the benefits of using NtCreateFile() instead
> of CreateFile().
>

IIRC, NtCreateFile is significantly cheaper if you already have a file
handle, especially on network drives where the name to handle translation
and open are fairly expensive.  The original reason was purely
performance (since I believe my company paid for some of this
optimization).

-- 
Brian Ford
Senior Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
the best safety device in any aircraft is a well-trained pilot...

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