Hi Werner,
On Sep 23, 2010, at 12:04 PM, Werner Benger wrote:
> Hi,
>
> how would one create a compound data type that consists out of two strings?
> Loose equivalent in C:
>
> struct Type
> {
> char *first, *second;
> };
>
> In HDF5, it would be a compound type made from two type ID's that are
> either "hid_t H5Tvlen_create( hid_t base_type_id )" or H5T_C_S1, to
> be inserted as a member "first" and "second" to a
>
> hid_t TypeID = H5Tcreate( H5T_COMPOUND, size_t size );
> H5Tinsert( TypeID, "first" , 0 , H5T_C_S1 );
> H5Tinsert( TypeID, "second", size_t offset, H5T_C_S1 );
>
>
> However, what would be the "size" of this compound data type and the
> offset of the second member?
>
> It would seem this presumably simple approach can't work (would be nice
> to document that around H5Tcreate() or H5Tinsert() ) ?
>
> Alternatively, it should be possible to create an array of strings, using
>
> hsize_t dims[1] = { 2 };
> H5Tarray_create( H5T_C_S1, 1, dims);
>
> but this would be less verbose as the data type doesn't get named members.
>
> Any hints/recommendation on what would work best?
Nope, having two VL-strings as fields in a compound datatype is fine.
Just create a variable length string datatype (tid = H5Tcopy(H5T_C_S1);
H5Tset_size(tid, H5T_VARIABLE); ) and then insert that for each field, at the
appropriate offset.
Quincey
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