Re: 64-bit file operations (lseek64() etc) misbehaving

[Igor Pechtchanski <pechtcha at cs dot nyu dot edu>]

Mike,

FYI, the following works just fine on my system (Win2k, Cygwin 1.5.9, 11G
harddrive):

------------------------------------------------------------------------------
#include <sys/types.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

#define BYTE (sizeof(unsigned char))
#define KB (1024 * BYTE)
#define MB (1024 * KB)
#define GB (1024 * MB)

int main(int argc, char *argv[]) {
	int fd;
	off_t maxblock;
	if ((fd = open("/dev/sda", O_RDONLY)) < 0) {
		perror("open failed"); exit(2);
	}
	if ((maxblock = lseek(fd, 0, SEEK_END)) == (off_t) -1) {
		perror("lseek failed"); exit(3);
	}
	printf("%llub, %lluKb, %lluMb, %lluGb in /dev/sda\n", maxblock,
	       maxblock / KB, maxblock / MB, maxblock / GB);
	close(fd);
	return 0;
}
------------------------------------------------------------------------------

If I replace "/dev/sda" by "\\\\.\\PhysicalDrive0" everywhere, however, I
get the same result you do.  Food for thought.
HTH,
	Igor

On Wed, 31 Mar 2004, Mike Brown wrote:

> Hi Igor,
>
> Yes the a.out a.exe thing is a typo.  I've read the page on special
> filenames.  You can use the POSIX names or you can open the Windows
> device namespace name.  Either way, my problem isn't with opening and
> reading from the disk device.  That works fine.  My problem is with
> lseek() not being able to seek past the 4Gb boundary.
>
> Thanks.
>
> On Wed, Mar 31, 2004 at 02:14:18PM -0500, Igor Pechtchanski wrote:
> > On Wed, 31 Mar 2004, Mike Brown wrote:
> >
> > > Hi,
> > >
> > > cygwin 1.5.9-1 on Windows XP Service Pack 1.
> > >
> > > I need 64-bit versions of lseek() and friends.  No prototype exists for
> > > lseek64().  I've searched the archives on the list and many claim that
> > > 64-bit support is "automatic" and lseek() resolves at compile time to
> > > lseek64().  This isn't happening for me.  Is there a compile time
> > > define I need to make this happen?
> > >
> > > [snip]
> > > Here's a simple example app I'm using.  I run via:  a.out PhysicalDrive0
> >
> > Michael,
> >
> > I don't know if it's related to the problem you're having, but I'm sure
> > you've read <http://cygwin.com/cygwin-ug-net/using-specialnames.html>,
> > right?  Try compiling a Linux version with "#define lseek64 lseek", and
> > use ./a.exe /dev/sda (note that Cygwin gcc produces a.exe, not a.out, by
> > default, so I assume the above is a typo or the result of an explicit "-o"
> > flag).
> >       Igor
> >
> > > -----------------------
> > > /* #define LINUX */
> > > #define WIN32
> > >
> > > [snip]
> > > #ifdef WIN32
> > >         /* automatically add the \\.\ crap in front */
> > >         sprintf(filename, "\\\\.\\%s", argv[1]);
> > > #else
> > >         sprintf(filename, "%s", argv[1]);
> > > #endif
> > > [snip]
> > > #ifdef WIN32
> > >         maxblock = lseek(fd, 0, SEEK_END);
> > > #else
> > >         maxblock = lseek64(fd, 0, SEEK_END);
> > > #endif

-- 
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