[gdal-dev] New OSGeo4W Package, virtual io activity, beta

[Frank Warmerdam]

Folks,

I have prepared a new OSGeo4W "gdal-dev" package capturing the state
of GDAL as of lunchtime today.  This is a windows package as part of
OSGeo4W.  To use it install OSGeo4W and in the advanced install add
the "gdal-dev" package.  Then in the OSGeo4W command shell type "gdaldev"
to switch to the current development status package.

   http://osgeo4w.osgeo.org/

I also made a small change today to have "gdalinfo --formats" report drivers
that support virtual io.  Virtual IO support in a driver means that the
driver does all it's io through the VSI*L virtual io layer,and that it
can be used for memory access (/vsimem), reading from gzip files or zip files
(/vsigzip, /vsizip) and potentially other io virtualization games.

Relatively few formats report support for virtual io but that is mostly because
we have not made a consistent effort to set the GDAL_DCAP_VIRTUALIO metadata
on drivers that do support it in the past.  I am hoping we can make a push to
flesh this out.  A quick way to test (read) virtual io access is to put the
data file (say test.tif) in a directory by itself (say testdir) and then
do:

   gdalinfo --mempreload testdir /vsimem/test.tif

the --mempreload switch tells gdalinfo to first load all files in the named
directory into memory under the /vsimem/ virtual directory.  So in the above
case we would see the test.tif file being accessed through virtual io.

A safe driver can be marked in the registration method with a line like:

   poDriver->SetMetadataItem(GDAL_DCAP_VIRTUALIO, "YES");

Currently the only application I know of that makes use of this is the
MapServer WCS 1.1 support which uses this as a clue that working results
do not need to be written to disk.  But I'd like to make this more trustworthy
for other applications to use.

Lastly, our Beta1 date of December 8th went by without anyone acting on it.
I shall attempt to package a Beta1 tomorrow morning or afternoon.

Best regard,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent