[gdal-dev] vsipreload: enabling VSI Virtual File API for regular I/O

[Etienne Tourigny]

On Sun, May 26, 2013 at 11:46 AM, Even Rouault <even.rouault at mines-paris.org
> wrote:

> Hi,
>
> I've just commited in trunk a new file port/vsipreload.cpp.
>
> This file is the source code for a standalone shared library that can be
> LD_PRELOAD'ed as an overload of libc to enable VSI Virtual FILE API to be
> used
> with binaries using regular libc I/O API.
>
> WARNING: Linux glibc ONLY. Might work with some adaptations (mainly around
> 64bit symbols) on other Unix systems
>
> Compile:
> g++ -Wall -fPIC port/vsipreload.cpp -shared -o vsipreload.so -Iport \
>         -L. -L.libs -lgdal
>
> Examples :
>
> LD_PRELOAD=vsipreload.so gdalinfo \
>         /vsicurl/http://download.osgeo.org/gdal/data/ecw/spif83.ecw


Even,

I have built vsipreload with a fresh build of svn trunk, but I get the
following error:

$ g++ -Wall -fPIC port/vsipreload.cpp -shared -o vsipreload.so -Iport -L.
-L.libs -lgdal
$ LD_PRELOAD=vsipreload.so gdalinfo         /vsicurl/
http://download.osgeo.org/gdal/data/ecw/spif83.ecw
ERROR: ld.so: object 'vsipreload.so' from LD_PRELOAD cannot be preloaded:
ignored.
ERROR 4: `/vsicurl/http://download.osgeo.org/gdal/data/ecw/spif83.ecw' not
recognised as a supported file format.

gdalinfo failed - unable to open '/vsicurl/
http://download.osgeo.org/gdal/data/ecw/spif83.ecw'.

Is there a way to find out why it cannot be preloaded? Perhaps the
compilation options should be tweaked?

Thanks,
Etienne

My system is Linux Mint 13 ubuntu (quantal), gcc version 4.7.2, 64bits,
3.5.0-30-generic kernel


>
> LD_PRELOAD=vsipreload.so gdalinfo \
>  'HDF4_EOS:EOS_GRID:"/vsicurl/
> http://download.osgeo.org/gdal/data/hdf4/MOD09Q1G_EVI.A2006233.h07v03.005.2008338190308.hdf
> ":MODIS_NACP_EVI:MODIS_EVI'
>
> LD_PRELOAD=vsipreload.so ogrinfo \
>          /vsicurl/
> http://svn.osgeo.org/gdal/trunk/autotest/ogr/data/testavc -ro
>
> LD_PRELOAD=vsipreload.so ogrinfo -ro \
>
> /vsizip//vsicurl/
> http://download.osgeo.org/gdal/1.10.0/gdalautotest-1.10.0.zip/gdalautotest-1.10.0/ogr/data/testavc
>
> It can work even with non GDAL binaries :
>
> LD_PRELOAD=vsipreload.so h5dump -d /x \
>         /vsicurl/
> http://download.osgeo.org/gdal/data/netcdf/utm-big-chunks.nc
>
> LD_PRELOAD=vsipreload.so sqlite3 \
>          /vsicurl/http://download.osgeo.org/gdal/data/sqlite3/polygon.db \
>         "select * from polygon limit 10"
>
> This can work with all VSI Large File API filesystems : /vsizip/ ,
> /vsitar/,
> /vsisubfile/ , etc...
>
> This is still a bit experimental in the sense that only the most common
> glibc
> I/O API have been overloaded. If exotic ones are used with /vsi files,
> crashes
> are likely.
>
> --
> Geospatial professional services
> http://even.rouault.free.fr/services.html
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>
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