old_contents: #!/usr/bin/python
  
  import os
  import sys
  import hashlib
  
  inputfile  = sys.argv[1]
  outputfile = sys.argv[2]
  
  header = 32
  tail   = 272
  
  with open(inputfile, 'rb') as fin, open(outputfile, 'wb') as fout:
      data = fin.read()
      fout.write(data)
  
      size = fin.tell()
      fin.seek(header, 0)
      size -= (header + tail)
  
      data = fin.read(size)
      h = hashlib.sha256(data);
      digest = h.digest()[:4]
  
      fout.seek(4, 0)
      fout.write(digest)
  
new_contents: #!/usr/bin/python
  
  import sys
  import hashlib
  
  inputfile  = sys.argv[1]
  outputfile = sys.argv[2]
  
  header = 32
  tail   = 272
  
  with open(inputfile, 'rb') as fin, open(outputfile, 'wb') as fout:
      data = fin.read()
      fout.write(data)
  
      size = fin.tell()
      fin.seek(header, 0)
      size -= (header + tail)
  
      data = fin.read(size)
      h = hashlib.sha256(data);
      digest = h.digest()[:4]
  
      fout.seek(4, 0)
      fout.write(digest)
  
subject: remove unusing imported