[gdal-dev] Does /vsis3 work for HDF4?

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[gdal-dev] Does /vsis3 work for HDF4?

Joe Lee
Hi,

  I have a quick question.
  I know that /vsis3 work for HDF5.

  How about HDF4?
  Does /vsis3 also work for HDF4?

  Regards,


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Re: Does /vsis3 work for HDF4?

James McClain-2
Hello,

I don't believe that it does currently.

Originally, support for HDF5 and NetCDF both used the cpl_userfaultfd mechanism https://github.com/OSGeo/gdal/blob/master/gdal/port/cpl_userfaultfd.cpp).  The thing that prevented HDF4 from using that mechanism was that its underlying library did not have the ability to operate on a block of memory (the cpl_userfaultfd provides a user-mode page fault handler that fills pages on demand using the VSI mechanism).

It is my recollection that a more direct method was found for HDF5 so that it no longer uses cpl_userfaultfd; perhaps a similarly more direct mechanism exists in HDF4?  I do not know whether it does or does not.

Sincerely,
James McClain
 

On Mon, May 20, 2019 at 2:45 PM Joe Lee <[hidden email]> wrote:
Hi,

  I have a quick question.
  I know that /vsis3 work for HDF5.

  How about HDF4?
  Does /vsis3 also work for HDF4?

  Regards,

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Re: Does /vsis3 work for HDF4?

Even Rouault-2
In reply to this post by Joe Lee
>
>   How about HDF4?
>   Does /vsis3 also work for HDF4?

Not directly, as to the best of my knowledge, but you're likely more in a
postion o confirm, libhdf4 has no I/O abstraction layer.
On Linux, you might try the vsipreload trick:
https://lists.osgeo.org/pipermail/gdal-dev/2013-May/036359.html

Even

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