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Today's Topics:
1. which typefor this FFI call (PICCA Frederic-Emmanuel)
----------------------------------------------------------------------
Message: 1
Date: Sat, 24 Jun 2017 13:47:44 +0000
From: PICCA Frederic-Emmanuel
<frederic-emmanuel.pi...@synchrotron-soleil.fr>
To: "Beginners@haskell.org" <Beginners@haskell.org>
Subject: [Haskell-beginners] which typefor this FFI call
Message-ID:
<a2a20ec3b8560d408356cac2fc148e53bb384...@sun-dag3.synchrotron-soleil.fr>
Content-Type: text/plain; charset="us-ascii"
Hello
I would like to create a binding for this function [1].
herr_t H5Literate( hid_t group_id, H5_index_t index_type, H5_iter_order_t
order, hsize_t *idx, H5L_iterate_t op, void *op_data )
My "only" problem is with the op and op_data part.
Here the C op signature[2]
op -> herr_t (*H5L_iterate_t)( hid_t g_id, const char *name, const H5L_info_t
*info, void *op_data)
What I would like to do is to create an Haskell function which allows to return
what is contained under the op_data.
What I understand from this is that I give the H5Literate function an op
function which is executed for each group of my hdf5 file.
So the op method is called with the releavant parameters.
The op_data can be use to accumulate things during the traversal.
H5Literate :: Hid -> Index -> Order -> Maybe HSize -> H5Iterate -> _ -> _
type H5Iterate = Hid -> ByteString -> Info -> _ -> _
So it seems to me that I need to use a State inorder to do the accumulation.
For exemple,I want to collect each group names and accumulate then in a list.
Somy questioniswhat should be the signature of both function.
I have also the fealing that the return type MUST have a Storableinstance.
Thanks for your help
Frederic
[1] https://support.hdfgroup.org/HDF5/doc/RM/RM_H5L.html#Link-Iterate
[2] https://support.hdfgroup.org/HDF5/doc/RM/RM_H5L.html#Link-Visit
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