nqm_for_scantable.py

"""Mini tool to modify nqm to one compatible with CASA's scantable.

Usage:
    $ python nqm_for_scantable.py <nqmname>

Notes:
    User can use wildcard '*' in <nqmname> for batch process.

"""

# standard library
import sys

# module constants
FITS_HEADER_SIZE = 23040 # 8*2880 bytes


# functions
def modify(nqmname):
    # read nqm
    with open(nqmname, 'rb') as f_nqm:
        # read header part
        h_nqm = b''
        while True:
            h_nqm += f_nqm.read(1)
            if h_nqm.endswith(b' LS '):
                break

        h_nqm = h_nqm.rstrip(b'LS ')
        d_nqm = b'LS ' + f_nqm.read()

    # adjust header size to 23040 bytes
    if len(h_nqm) == FITS_HEADER_SIZE:
        pass
    elif len(h_nqm) < FITS_HEADER_SIZE:
        h_nqm += b' ' * (FITS_HEADER_SIZE-len(h_nqm))
    else:
        h_nqm = h_nqm.split(b'HISTORY', 1)[0]
        h_nqm += b'END'
        h_nqm += b' ' * (FITS_HEADER_SIZE-len(h_nqm))

    # create modified nqm
    nqmname = nqmname.rstrip('.nqm') + '.mod.nqm'
    with open(nqmname, 'wb') as f_nqm:
        f_nqm.write(h_nqm + d_nqm)


# main program
if __name__ == '__main__':
    args = sys.argv[1:]

    if len(args) == 0:
        print(__doc__)
        sys.exit()

    for nqmname in args:
        print('modifying: ' + nqmname)
        modify(nqmname)