check dHCP subject ID for validity.

is_valid_id.py

#! /usr/bin/env python3

# check subject ID for validity.
usage="""
usage:

is_valid_id.py <dhcp_subject_id>

example: ./is_valid_id.py CC01253XX08

No output if valid, stdout and nonzero exit if not valid

"""

def valid_dhcp_checksum (pid, verbose=True):
  # luhnCheckFast
  # converted from http://dev.paediatrics.co.uk/connectome/
  if len(pid) < 11:
     if verbose: print ("Invalid study ID (too short)")
     return False
  if len(pid) > 11:
     if verbose: print ("Invalid study ID (too long)")
     return False

  numeric = [int(x) for x in filter( lambda x: x in '0123456789', pid )]
  mid_id = numeric[:-2]
  luhn_id = numeric[-2:]

  ca = 0
  sm = 0
  mul = 1
  for i in mid_id:
     ca = i * mul
     sm += ca - (ca>9)*9
     mul ^= 3

  return sm == numeric[-2] * 10 + numeric[-1]


if __name__ == '__main__':
  import sys
  if len(sys.argv) != 2:
    print (usage)
    sys.exit()

  if not valid_dhcp_checksum((sys.argv[1].lstrip('sub-'))):
    sys.exit(sys.argv[1] + " is not a valid study ID")