[gdal-dev] Resquest for comments (RFC 36)

[Daniel Morissette]

I like the idea, especially since it can increase performance in some 
cases. However unless I'm mistaken the proposed patch seems to fall back 
on the regular test-open loop when the GDALOpenInternal() call with the 
explicit driver name failed, no matter why it failed. e.g. I specify the 
invalid "hfa:test.tif" open string, then I should get a NULL return 
value and not a handle to a TIFF file.

The patch would need to be reworked for this, but I think that if the 
GetDriverByName() call succeeds (i.e. the driver name prefix is 
recognized by GDAL) and the call to poDriver->pfnOpen() fails then we 
should return NULL to the application code (and not fall back on the 
test-open loop). OTOH, if the GetDriverByName() lookup failed, then we 
should fall back on the test-open loop.

Also, if we implement this mechanism in GDAL, then we'd have to provide 
it in OGR as well to be consistent.

Daniel


On 11-10-03 08:02 PM, Ivan Lucena wrote:
> Hi All,
>
> RFC 36: http://trac.osgeo.org/gdal/wiki/rfc36_open_by_drivername
>
> The goal of RFC 36 is to save processing time by telling GDALOpen what driver to use, avoiding the driver-probing mechanism (Where all drivers are asked to checked if they recognize the file).
>
> It works by adding the driver name before the file-name as in GDALOpen("hfa:example_file.img").
>
> *It is optional*. It does not invalidate the current simple filename entry that most of the drivers use nor the more complex "filename" string formats used by a few drivers (with things like server-name, port-number, table-name).
>
> It is intended to speed up applications or scripts that need to process a large number of datasets when it already knows what driver to use.
>
> Command line use should not be affect considerably in terms of speed but it adds the option to avoid the wrong driver from taking precedence from the intended one (#3043), ex.:
>
> $ gdalinfo ntif:/autotest/gdrivers/data/rgb.ntf"
>
> If you want to try it, a patch that implements this proposed change is available on ticket 3043 http://trac.osgeo.org/gdal/ticket/3043
>
> Please take a look and send us your comments.
>
> Regards,
>
> Ivan
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-- 
Daniel Morissette
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