Hi Marc,
> On Sep 16, 2015, at 2:54 AM, [email protected] wrote:
>
> Hi all,
>
> I've just found a weird construct in one of our CGNS/HDF5 files (part of
> h5dump below).
> We have an external link to another file and inside the external link itself
> there is a 'local' group.
> The group inside actually masks a group of same name in the target file (see
> bc_1_8 below).
> We did obtain such a file because of a bug in our application, it uses to
> replace a group with an external
> link having the same name but without deleting the original group.
>
> I wonder if:
>
> 1. yes this is the expected behavior, the link is always read first so that
> you can use this feature to partly mask the target sub-tree
> 2. no, this file shows a bad construct, should be corrected and HDF5 should
> forbid such
> 3. side-effect, it is not a feature but you can build such a file, as long as
> we do not change implementation the side effect is... a feature (oups!)
Hmm, I think 1 & 3 are basically the same, and that’s what the HDF5
library is supposed to do. Basically, the library will attempt to traverse the
external link’s path, and if it encounters soft or external links in the
destination file’s group hierarchy, it’ll just keep resolving those as it
encounters them. Since the external links are stored as “plain” strings in the
source HDF5 file, there’s no reference to the “actual” object in the
destination file, just a path in that file to traverse to reach the object.
Make sense? :-)
Quincey
> -MP-
>
> EXTERNAL_LINK " link" {
> TARGETFILE "mesh.cgns"
> TARGETPATH "/Base#1/Zone#1/ZoneGridConnectivity"
> GROUP "/Base#1/Zone#1/ZoneGridConnectivity" {
> ATTRIBUTE "flags" {
> DATATYPE H5T_STD_I32LE
> DATASPACE SIMPLE { ( 1 ) / ( 1 ) }
> DATA {
> (0): 0
> }
> }
> ATTRIBUTE "label" {
> DATATYPE H5T_STRING {
> STRSIZE 33;
> STRPAD H5T_STR_NULLTERM;
> CSET H5T_CSET_ASCII;
> CTYPE H5T_C_S1;
> }
> DATASPACE SCALAR
> DATA {
> (0): "ZoneGridConnectivity_t"
> }
> }
> ATTRIBUTE "name" {
> DATATYPE H5T_STRING {
> STRSIZE 33;
> STRPAD H5T_STR_NULLTERM;
> CSET H5T_CSET_ASCII;
> CTYPE H5T_C_S1;
> }
> DATASPACE SCALAR
> DATA {
> (0): "ZoneGridConnectivity"
> }
> }
> ATTRIBUTE "type" {
> DATATYPE H5T_STRING {
> STRSIZE 3;
> STRPAD H5T_STR_NULLTERM;
> CSET H5T_CSET_ASCII;
> CTYPE H5T_C_S1;
> }
> DATASPACE SCALAR
> DATA {
> (0): "MT"
> }
> }
> GROUP "bc_1_8" {
> ATTRIBUTE "flags" {
> DATATYPE H5T_STD_I32LE
> DATASPACE SIMPLE { ( 1 ) / ( 1 ) }
> DATA {
> (0): 0
> }
> }
> }
>
> --
> -- ------------------------------------------------------------
> -- Marc POINOT [ONERA/DMFN] Tel:+33.1.46.73.42.84
> -- Avertissement/disclaimer http://www.onera.fr/en/emails-terms
> -- ------------------------------------------------------------
>
>
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