Le mercredi 23 mars 2016 20:11:43, Vish Uma a écrit : > I am using vsicurl to read a given extent of values from a GeoTIFF file > over HTTP. I found that the library is making multiple requests with > different range headers(8 requests in my case) to read all of the data > that is needed. Does VSICURL support reading these bytes ranges in a > single request by specifying the range as "Range: bytes=100-200, 300-400".
VSICURL yes, but the readers that use it, generally no since that require them to be modified to "plan" their reads in advance, which is sometimes not possible, or not practical. > This entry in the 1.9 release notes seems to suggest it is possible > "VSI*L: Add ReadMultiRange?() virtual method to read several ranges of > data in single call; add an optimized implementation for /vsicurl/" > (https://trac.osgeo.org/gdal/wiki/Release/1.9.0-News) but it is not what I > am observing. This is only used in the GTiff driver if specifying GTIFF_DIRECT_IO=YES as configuration option / environment variable. This is restricted to a few formulations of GeoTIFF though. See http://gdal.org/frmt_gtiff.html ( there was already some support in 1.9, but with more restrictions, like limited to single band datasets. ) > Thank You,Vish -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
