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implementing the attribute callbacks in a VOL plugin

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implementing the attribute callbacks in a VOL plugin

dimstamat
This post was updated on .
Hi all,

Regarding my previous question about an extra call of H5Fclose, there was
indeed an extra open handle. Now everything works perfectly!
Now I have a question about the attribute callbacks of a VOL plugin and the
datatype. I am guessing on attribute create we have to store the specified
datatype and dataspace using the custom VOL plugin. The question is how
will we restore them, since for example the datatype has to be in the HDF5
format (H5T_t type), it is not something custom like the VOL objects. I saw
that calling H5I_register() on a datatype generates a location ID, but it
is not working properly.
What is the correct procedure of implementing attribute callbacks for a VOL
plugin? Also I saw that the datatype callbacks are not invoked in the
native HDF5 when creating and accessing string attributes.
For example, when creating a string attribute, closing it, then opening it
again and getting its datatype it should return a location ID of its
datatype. This is quite confusing, since how will the VOL plugin create
these HDF5 specific objects?

Thanks,

Dimos

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Re: implementing the attribute callbakcs in a VOL plugin

Mohamad Chaarawi

Usually in custom VOL plugin, the easiest way to store the datatype and dataspace for an attribute or dataset is to serialize them and store them as a blob.

Look into the function H5Tencode/decode() and H5Sencode/decode().

 

Thanks,

Mohamad

 

From: Hdf-forum <[hidden email]> on behalf of Dimos Stamatakis <[hidden email]>
Reply-To: hdf-forum <[hidden email]>
Date: Friday, May 27, 2016 at 1:20 AM
To: hdf-forum <[hidden email]>
Subject: [Hdf-forum] implementing the attribute callbakcs in a VOL plugin

 

Hi all,

 

Regarding my previous question about an extra call of H5Fclose, there was indeed an extra open handle. Now everything works perfectly!

Now I have a question about the attribute callbacks of a VOL plugin and the datatype. I am guessing on attribute create we have to store the specified datatype and dataspace using the custom VOL plugin. The question is how will we restore them, since for example the datatype has to be in the HDF5 format (H5T_t type), it is not something custom like the VOL objects. I saw that calling H5I_register() on a datatype generates a location ID, but it is not working properly.

What is the correct procedure of implementing attribute callbacks for a VOL plugin? Also I saw that the datatype callbacks are not invoked in the native HDF5 when creating and accessing string attributes.

For example, when creating a string attribute, closing it, then opening it again and getting its datatype it should return a location ID of its datatype. This is quite confusing, since how will the VOL plugin create these HDF5 specific objects?

 

Thanks,

 

Dimos


_______________________________________________
Hdf-forum is for HDF software users discussion.
[hidden email]
http://lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org
Twitter: https://twitter.com/hdf5
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