H5F_REOPEN returns a new file identifier for an already-open HDF5 file, as specified by
file_id. Both identifiers share caches and other information. The only difference between the identifiers is that the new identifier is not mounted anywhere and no files are mounted on it.
Note that there is no circumstance under which H5F_REOPEN can actually open a closed file; the file must already be open and have an active
file_id. E.g., one cannot close a file with H5F_CLOSE (file_id) then use H5F_REOPEN
(file_id) to reopen it.
The new file identifier should be closed by calling H5F_CLOSE when it is no longer needed.