[Rd] file.info() on WinXP/NTFS > 2Gb
hb at maths.lth.se
Sat Feb 18 22:10:39 CET 2006
On 2/18/06, Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:
> On Sat, 18 Feb 2006, Henrik Bengtsson wrote:
> > Hi,
> > on WinXP Pro SP2 with NTFS, I noticed that file.info() under
> > Rv2.2.1pat (2006-02-09) does not report the correct file size if the
> > file is >= 2^31 bytes (2GB). Is this problem known? Is this related
> > to the note in ?file.info:
> > "Some (broken) systems allow files of more than 2Gb to be created but
> > not accessed by the 'stat' system call. Such files will show up as
> > non-readable (and very likely not be readable by any of R's input
> > functions)."
> Yes, no (although I have forgotten which file system that was). The code
> relies on the stat call. On a modern OS this comes from POSIX and says
> off_t st_size; /* total size, in bytes */
> It looks the corresponding MinGW/MSVCRT type is _off_t which is long, and
> on Windows that is a 32-bit type. This can be avoided by
> calling stati64 rather than stat: that is incorrectly documented in my
> copy of MSDN library, but I have been able to find the correct
> incantation so this will be fixed in R-devel soon.
Thank you very much for this.
> > Example:
> > # Create a 2Gb(!) file, report file.info()$size, and remove the file.
> > fname <- "tmp.Rbin";
> > con <- file(fname, open="w+b");
> > size <- 2^31-1; # OK
> > size <- 2^31; # Not OK
> > seek(con, where=size-1, rw="write");
> > writeBin(con=con, as.integer(0), size=1);
> > close(con);
> > print(file.info(fname)$size);
> > file.remove(fname);
> > With size = c(2^31-1,2^31), file.info() reports file size
> > c(2147483647,-2147483648). This looks to me like a non-signed to
> > signed integer case.
> > Note that the above code does indeed create files >2Gb on WinXP with
> > NTFS; I've created files about 6Gb this way.
> > BTW, about seek() on Windows: I noticed the warning about using
> > seek() on Windows (see ?seek): "We have found so many errors in the
> > Windows implementation of file positioning that users are advised to
> > use it only at their own risk, and asked not to waste the R
> > developers' time with bug reports on Windows' deficiencies.". Not
> > going to bug report, but I haven't noticed any problems this far.
> > What errors/symptoms are expected? Is regardless of file system used,
> > e.g. FAT, NTFS?
> Look in the bug repository. There have been issues with text files and
> with files > 2Gb, and others.
> Brian D. Ripley, ripley at stats.ox.ac.uk
> Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
> University of Oxford, Tel: +44 1865 272861 (self)
> 1 South Parks Road, +44 1865 272866 (PA)
> Oxford OX1 3TG, UK Fax: +44 1865 272595
Mobile: +46 708 909208 (+1h UTC)
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