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c++hdf5

HDF5 (using C++ API): Writing individual fields of Attribute compound data erasing other fields

While writing individual fields of Compound data type of an Attribute results other fields data got erased. Is there any way we can write individual fields at a time to an attribute compound data?

Note 1: Writing data for individual fields of a compound data type works for Dataset

Note 2: I know writing all data fields works, but we need to write individual fields

Note 3: Reading individual fields of a compound data type works for Attribute and Dataset

 #define REAL_FIELD_NAME "Real"
#define IMAGINARY_FIELD_NAME "Imag"
typedef  struct {
    double real = 8;
    double imag = 9;
} compl;
int main()
{
    //Create a file
    std::string _file_name("test.h5");
    H5::H5File _file(_file_name, H5F_ACC_TRUNC);

    //Create dataspace
    hsize_t _dims = 1;
    H5::DataSpace dataspace(1, &_dims);

    //Create compound data type with two fields, 1. Real, 2. Imag
    H5::CompType _comp_dt((2 * sizeof(double)));
    _comp_dt.insertMember(REAL_FIELD_NAME, HOFFSET(compl, real), H5::PredType::NATIVE_DOUBLE);
    _comp_dt.insertMember(IMAGINARY_FIELD_NAME, HOFFSET(compl, imag), H5::PredType::NATIVE_DOUBLE);

    //Create Dataset with compound data type
    H5::DataSet _dset(_file.createDataSet("/test_dataset", _comp_dt, dataspace));
    //Create Attribute with compound data type
    H5::Attribute _attr(_dset.createAttribute("/test_attr", _comp_dt, dataspace));


    double _real = 9;
    H5::CompType _comp_dt_real(sizeof(double));
    _comp_dt_real.insertMember(REAL_FIELD_NAME, 0, H5::PredType::NATIVE_DOUBLE);
    //Writing data to dtaset, only Real field
    _dset.write(&_real, _comp_dt_real);
    //Writing data to attribute, only Real field
    _attr.write(_comp_dt_real, &_real);

    double _imag = 8;
    H5::CompType _comp_dt_imag(sizeof(double));
    _comp_dt_imag.insertMember(IMAGINARY_FIELD_NAME, 0, H5::PredType::NATIVE_DOUBLE);
    //Writing data to dtaset, only Imag field
    _dset.write(&_imag, _comp_dt_imag);
    //Writing data to Attribute, only Imag field, which clears Real field
    _attr.write(_comp_dt_imag, &_imag);

    /*following works*/
    compl _real_imag;

    H5::Attribute _attr_2(_dset.createAttribute("/test_attr_2", _comp_dt, dataspace));
    H5::CompType _comp_dt_cmpl(sizeof(compl));
    _comp_dt_cmpl.insertMember(REAL_FIELD_NAME, HOFFSET(compl, real), H5::PredType::NATIVE_DOUBLE);
    _comp_dt_cmpl.insertMember(IMAGINARY_FIELD_NAME, HOFFSET(compl, imag), H5::PredType::NATIVE_DOUBLE);
    _attr_2.write(_comp_dt_cmpl, &_real_imag);

    return 0;
}

Results: enter image description here

Solution

  • I got the response from HDF5 forum. Writing parts of attribute values not allowed.

    Only for reference: https://forum.hdfgroup.org/t/writing-individual-fields-of-compound-data-of-an-attribute-erasing-remaining-fields/7612