From ripley at stats.ox.ac.uk  Sat Feb 18 21:15:47 2006
From: ripley at stats.ox.ac.uk (Prof Brian Ripley)
Date: Sat, 18 Feb 2006 20:15:47 +0000 (GMT)
Subject: [Rd] file.info() on WinXP/NTFS > 2Gb
In-Reply-To: <59d7961d0602181133r2e22ccechdafb31aaf8e85b47@mail.gmail.com>
References: <59d7961d0602181133r2e22ccechdafb31aaf8e85b47@mail.gmail.com>
Message-ID: <Pine.LNX.4.64.0602181946230.10789@gannet.stats.ox.ac.uk>

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.

> 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



[Rd] file.info() on WinXP/NTFS > 2Gb
Prof Brian Ripley