Re: Create files larger than 2GB with open or CreateFile?

"Ben Voigt [C++ MVP]" <bvoigt@newsgroup.nospam>
Wed, 27 May 2009 15:30:44 -0500
Bill Davy wrote:

Isn't there something about the type of the filing system? It needs
to be NTFS. At least, something like that rings a bell.

Sure, but NTFS has been around for a long time, since at least NT 3.5x.


"Ben Voigt [C++ MVP]" <bvoigt@newsgroup.nospam> wrote in message

"Nick Shallery" <> wrote in message

SetFilePosition? you mean is SetFilePointer?
Yes, The new API SetFilePointerEx can be used.

Yeah that's what I meant. Anyhow the MSDN docs for those functions
are messed up b/c I don't think SetFilePointer was introduced in
Win2k, but that's what the page says.

OT: The suspicion is that someone doesn't understand the difference
between having an OS supporting a library function (that is having an
implementation) and Microsoft offering support for an OS in the
sense of security patches, and thus is removing the old OSes from
the programmer documentation as their security support expires.

"Ben Voigt [C++ MVP]" <bvoigt@newsgroup.nospam> 4?????

Tim Roberts wrote:

"Tim Jones" <> wrote:

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp> wrote:

"Tim Jones" <> wrote:

I'm moving a slew of code from Solaris to Windows and one issue
that I've run into is the creation of files larger than 2GB. I've
searched MSDN, but everything is either about DB access
or RAM. Under Solaris, I use a flag O_LARGEFILE in the modes flag.
However, I don't find a similar documentation for any Windows
file creation API menber. Is this possible (understanding
that we are only working with NTFS filesystems)?

Nothing special needed with the native APIs (CreateFile,
ReadFile, WriteFile).

That's what I thought, but I'm getting write failures as soon as
I hit the 2GB point.

That won't happen with standard WriteFile calls on an NTFS file
system. It can happen with a memory-mapped files. However,
remember that most removable devices (USB drives, USB flash
drives) use FAT file systems, where there are such limits.

Also even the Win32 APIs require special care, for example the
OVERLAPPED structure requires you to fill out two fields instead
of one, to identify the offset in a file > 2GB, SetFilePosition
requires special attention, etc.

Are you using stdio calls (fopen, fwrite)?

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