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#
# Copyright (C) 2006 Steve Ratcliffe
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
#
# Author: Steve Ratcliffe
# Create date: 10 Dec 2006
#
#
# Sets the check sum for the file. It is possible that the check sum
# is not actually checked by anything.
#
import sys
file = sys.argv[1]
print "file is", file
f = open(file)
cksum = 0
while 1:
block = f.read(512)
if not block: break
for c in block:
cksum -= ord(c)
cksum = (cksum & 0xff)
print "checksum is", cksum, hex(cksum)
if cksum != 0:
fw = open(file, "r+b")
fw.seek(15)
print "setting checksum, please re-check afterwards"
ch = chr(cksum)
print 'chr', ord(ch)
fw.write(ch)
fw.close()
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