[Gdal-dev] VSI file open/close issue

[Frank Warmerdam]

Frederic Claudel wrote:
> When using VSI* or VSI*L functions, it seems impossible to mix both, which
> means opening a file using VSIFOpen then closing it with VSIFCloseL.
> 
> Hence my question : how can I tell them apart ? In a new GDAL driver where I
> need to open lots of datasets, I'd like to re-use the opened file descriptor
> included in GDALOpenInfo to avoid unnecessary IO.
> 
> But that file descriptor can be opened by either of VSIFOpen or VSIFOpenL
> (when VSIFOpen fails) - by the way it's always closed using VSIFClose
> Should I use a RTTI function to guess the actual type?

Frederic,

Currently there is no way to distinguish VSI* from VSI*L handles.

However, the "fp" in the GDALOpenInfo is always a VSI* handle.  Drivers
that use VSI*L handes ignore the fp in the GDALOpenInfo and re-open the
file.  Files that don't successfully open with VSIFOpen() (ie. large files
on some systems) are opened with VSIFOpenL(), the header read, and then are
closed again.

Best regards,
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