[Gdal-dev] GDALOpenInfo->fp == NULL for large files?

[Frank Warmerdam]

Nick Bower wrote:
> I'm trying to debug the L1B driver - it's failing because poOpenInfo->fp 
> is NULL (starting a driver with this test is also in the driver 
> tutorial, and a raw driver also):
> 
> GDALDataset *L1BDataset::Open( GDALOpenInfo * poOpenInfo )
> 
> {
>    int i = 0;
>    if( poOpenInfo->fp == NULL )
>        return NULL; // Returns for no reason
> etc...
> 
> So I tried to figure out why fp is NULL.  The reason may be below?  I'm 
> not a C/C++ programmer to full understand this, so I can only get as far 
> as suspecting the problem has something to do with VSIFOpen/VSIFOpenL 
> conventions (let me know if I'm off).  With the latter, it is set to 
> NULL after reading for some reason, thus meaning (as far as i can tell) 
> the L1B, HDF4, raw etc drivers return in the first couple of lines of 
> initialization.  The file itself is only 85 Meg, so is not actually that 
> large.

Nick,

It is expected for poOpenInfo->fp to be NULL on some platforms when
the file is larger than 2GB (or possibly 4GB).  I see the L1B driver
is using the old technique of "adopting" the file pointer.  Formats
wishing to support larger than 2GB should not do this and ought to be
using the VSI*L API instead of the VSI* API.

Basically, the L1B driver is not "ready" for large files.

If you feel this should be rectified you could try updating the driver
yourself, or filing a bug report.  Since we don't have L1B files larger than
2GB, it would likely be necessary to have to check any fixes made.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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