Hi Meng, could you say more about what kind of data you are trying to read, and specifically what format it is in? ITensor isn't really intended as a library to help read in different files of various types, but only has support for two types of files currently: binary files which hold ITensor Library object data (such as ITensor, MPS, MPO, etc.) and uses a non-standard format, or else HDF5 files which we are starting to support.
If you are asking about HDF5 perhaps, those can be used in other contexts besides ITensor, such as to take the data out of an ITensor and use it in another library or code, or to read in data from another library or code. It is a portable and more organized solution for storing numerical data in files.