void h5_read(group g, std::string const& name, std::string& value) {
dataset ds = g.open_dataset(name);
h5::dataspace d_space = H5Dget_space(ds);
int rank = H5Sget_simple_extent_ndims(d_space);
if (rank != 0) TRIQS_RUNTIME_ERROR << "Reading a string and got rank !=0";
size_t size = H5Dget_storage_size(ds);
datatype strdatatype = H5Tcopy(H5T_C_S1);
H5Tset_size(strdatatype, size);
//auto status = H5Tset_size(strdatatype, size);
// auto status = H5Tset_size (strdatatype, H5T_VARIABLE);
std::vector<char> buf(size + 1, 0x00);
auto err = H5Dread(ds, strdatatype, H5S_ALL, H5S_ALL, H5P_DEFAULT, &buf[0]);
if (err < 0) TRIQS_RUNTIME_ERROR << "Error reading the string named" << name << " in the group" << g.name();
value = "";
value.append(&(buf.front()));
}
void h5_write(group g, std::string const& name, std::string const& value) {
datatype strdatatype = H5Tcopy(H5T_C_S1);
// auto status = H5Tset_size (strdatatype, H5T_VARIABLE);
//auto status = H5Tset_size(strdatatype, value.size() + 1);
H5Tset_size(strdatatype, value.size() + 1);
dataspace space = H5Screate(H5S_SCALAR);
dataset ds = g.create_dataset(name, strdatatype, space);
auto err = H5Dwrite(ds, strdatatype, H5S_ALL, H5S_ALL, H5P_DEFAULT, (void*)(value.c_str()));
if (err < 0) TRIQS_RUNTIME_ERROR << "Error writing the string named" << name << " in the group" << g.name();
}