Hi Gerd, thanks for reply. I guess my question was exactly why does not library provide automatic conversion? Is it too difficult/impossible to implement? I do not think that argument about user being unable to guess maximum size is a good one. If user provides size that is smaller than actual string library can always generate an error and let user correct the situation.
For me being able to use fixed-size strings on input would be a big improvement. Handling of variable-size strings is more complicated than of the fixed strings, one has to remember to call H5Dvlen_reclaim which may not be trivial thing as the code which reads the data and the code that uses/destroys the data may live in separate modules. Cheers, Andy Gerd Heber wrote on 2012-02-05: > Andrei, knowing that the lengths of all the strings in the file don't > exceed 32 doesn't help. The string type in the file is variable length > and not fixed length and the library doesn't do any kind of automatic > conversion for you. The call > > H5Tset_size(strType, 32); > > is well intended but wrong under the circumstances. It ought to be > > H5Tset_size(strType, H5T_VARIABLE); > > Have a look at > > http://www.hdfgroup.org/ftp/HDF5/examples/examples-by-api/hdf5- > examples/1_8/ C/H5T/h5ex_t_vlstring.c > > Best, G. > > -----Original Message----- From: hdf-forum-boun...@hdfgroup.org > [mailto:hdf-forum- boun...@hdfgroup.org] On Behalf Of Salnikov, Andrei > A. Sent: Thursday, February 02, 2012 2:18 PM To: HDF Users Discussion > List Subject: [Hdf-forum] Reading variable-length strings into > fixed-size char array > > Hi, > > I'd like to be able to read variable-length strings from HDF5 file into > fixed-size array but could not find a way to do it. What I have is this > dataset in the file: > > DATASET "eventcodes" { > DATATYPE H5T_COMPOUND { > H5T_STD_U16LE "code"; > H5T_STRING { > STRSIZE H5T_VARIABLE; > STRPAD H5T_STR_NULLTERM; > CSET H5T_CSET_ASCII; > CTYPE H5T_C_S1; > } "desc"; > } > I'd like very much to read this dataset into this in-memory structure: > > struct eventcodes { > uint16_t code; > char[32] desc; > }; > I know that all strings in file are shorter than 32 bytes, so this > should be > safe to do. When I define this in-memory data type for the structure: > > hid_t tid = H5Tcreate ( H5T_COMPOUND, sizeof(eventcodes) ) ; > H5Tinsert(tid, "code", 0, H5T_NATIVE_UINT16); > hid_t strType = H5Tcopy(H5T_C_S1); > H5Tset_size(strType, 32); > H5Tinsert(tid, "desc", 2, strType); > and try to read dataset with it I get errors from HDF5 about conversion > problem: > > #000: H5Dio.c line 174 in H5Dread(): can't read data > major: Dataset minor: Read failed #001: H5Dio.c line 337 in > H5D_read(): unable to set up type info major: Dataset minor: Unable > to initialize object > #002: H5Dio.c line 836 in H5D_typeinfo_init(): unable to convert > between > src and dest datatype > major: Dataset > minor: Feature is unsupported > #003: H5T.c line 4449 in H5T_path_find(): no appropriate function for > conversion path > major: Datatype > minor: Unable to initialize object > I thought that this kind of conversion would be pretty straightforward > and easy to implement, but apparently it's not done. Did I do something > wrong here or is my assumption just incorrect? > > I'm using 1.8.6 but would be happy to switch to new version if this > conversion is supported in later versions. > > Thanks, > Andy > > > > > > _______________________________________________ Hdf-forum is for HDF > software users discussion. Hdf-forum@hdfgroup.org > http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org > > > > _______________________________________________ Hdf-forum is for HDF > software users discussion. Hdf-forum@hdfgroup.org > http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org _______________________________________________ Hdf-forum is for HDF software users discussion. Hdf-forum@hdfgroup.org http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
