[GRASS-dev] fseeko() in libiostream

[Paul Kelly]

On Mon, 6 Oct 2008, Andrew Danner wrote:

> fseek is not the same as fseeko.
>
> int fseek(FILE *stream, long offset, int whence);
>
> int fseeko(FILE *stream, off_t offset, int whence);
>
> If large file support is enabled, fseeko will convert off_t to a 64 bit type 
> even on a 32-bit OS. I'm not sure if long will be 64 bit on a 64-bit OS for 
> fseek.
>
> r.in.xyz may work with large files using plain old fseek as long as r.in.xyz 
> doesn't make long seeks. ami_stream.h could potentially make long seeks 
> (e.g., skip the first 8GB of a 30GB file), though in practice, I'm not sure 
> that code that uses ami_stream (r.terraflow) actually uses this kind of 
> fseek. Still the interface is designed to potentially use long seeks and I 
> would be reluctant to simply replace fseeko with fseek in ami_stream.h.
>
> you may to add a #define to check the compiler type and use fseek only if 
> fseeko does not exist.

Right - I was vaguely aware of some configure checks for fseeko() but as 
ami_stream.h was the only file in GRASS using fseeko() I wasn't sure if it 
had been made redundant by something else. But looking closely at 
include/config.h, I see that we can conditionalise fseeko() on
#ifdef HAVE_LARGEFILES. After doing that, on Windows fseeko() is redefined 
to fseeko64() and all then works well.

A couple of further Windows compile errors in lib/iostream though:

sh-2.04$ make
c++ -I/c/grass/grass7/dist.i686-pc-mingw32/include -I/c/grass/extra/include -O2 -s -I/c/grass/extra/include  -D_FILE_OFFSET_BITS=64 -DPACKAGE=\""grasslibs"\"   -I/c/grass/grass7/dist.i686-pc-mingw32/include -o OBJ.i686-pc-mingw32/mm_utils.o -c mm_utils.cc
mm_utils.cc:38:22: sys/mman.h: No such file or directory
make: *** [OBJ.i686-pc-mingw32/mm_utils.o] Error 1

sh-2.04$ make
c++ -I/c/grass/grass7/dist.i686-pc-mingw32/include -I/c/grass/extra/include -O2 -s -I/c/grass/extra/include  -D_FILE_OFFSET_BITS=64 -DPACKAGE=\""grasslibs"\"   -I/c/grass/grass7/dist.i686-pc-mingw32/include -o OBJ.i686-pc-mingw32/mm_utils.o -c mm_utils.cc
c++ -I/c/grass/grass7/dist.i686-pc-mingw32/include -I/c/grass/extra/include -O2 -s -I/c/grass/extra/include  -D_FILE_OFFSET_BITS=64 -DPACKAGE=\""grasslibs"\"   -I/c/grass/grass7/dist.i686-pc-mingw32/include -o OBJ.i686-pc-mingw32/rtimer.o -c rtimer.cc
rtimer.cc:38:26: sys/resource.h: No such file or directory
make: *** [OBJ.i686-pc-mingw32/rtimer.o] Error 1

In the two respective cases I commented out the #includes for sys/mman.h 
and sys/resource.h and everything compiled fine. r.terraflow compiles fine 
too. So I'll simply remove those two #includes unless there's any 
objection?

Thanks for the feedback,

Paul