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

[Mike Brown <mbrown at emc dot com>]

Hi,

Yep that fixes me.  Thanks Igor.  Odd that the open() succeeds for
\\.\PhysicalDrive0.  _shrug_.  I'll gladly use /dev/sda.

-Mike

On Wed, Mar 31, 2004 at 04:18:49PM -0500, Igor Pechtchanski wrote:
> 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
> 
> -- 
> 				http://cs.nyu.edu/~pechtcha/
>       |\      _,,,---,,_		pechtcha@cs.nyu.edu
> ZZZzz /,`.-'`'    -.  ;-;;,_		igor@watson.ibm.com
>      |,4-  ) )-,_. ,\ (  `'-'		Igor Pechtchanski, Ph.D.
>     '---''(_/--'  `-'\_) fL	a.k.a JaguaR-R-R-r-r-r-.-.-.  Meow!
> 
> "I have since come to realize that being between your mentor and his route
> to the bathroom is a major career booster."  -- Patrick Naughton

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