def check_file(opt):
"""
Calculate the CRC of a file.
This algorithm uses the table_driven CRC algorithm.
"""
if opt.undefined_crc_parameters:
sys.stderr.write("{0:s}: error: undefined parameters\n".format(progname))
sys.exit(1)
alg = Crc(
width=opt.width, poly=opt.poly,
reflect_in=opt.reflect_in, xor_in=opt.xor_in,
reflect_out=opt.reflect_out, xor_out=opt.xor_out,
table_idx_width=opt.tbl_idx_width)
if not opt.reflect_in:
register = opt.xor_in
else:
register = alg.reflect(opt.xor_in, opt.width)
try:
with open(opt.check_file, 'rb') as f:
check_bytes = bytearray(f.read(1024))
while check_bytes != b"":
register = crc_file_update(alg, register, check_bytes)
check_bytes = bytearray(f.read(1024))
except IOError:
sys.stderr.write(
"{0:s}: error: can't open file {1:s}\n".format(progname, opt.check_file))
sys.exit(1)
if opt.reflect_out:
register = alg.reflect(register, opt.width)
register = register ^ opt.xor_out
return register
def _get_init_value(opt):
"""
Return the init value of a C implementation, according to the selected
algorithm and to the given options.
If no default option is given for a given parameter, value in the cfg_t
structure must be used.
"""
if opt.algorithm == opt.algo_bit_by_bit:
if opt.xor_in is None or opt.width is None or opt.poly is None:
return None
crc = Crc(width=opt.width,
poly=opt.poly,
reflect_in=opt.reflect_in,
xor_in=opt.xor_in,
reflect_out=opt.reflect_out,
xor_out=opt.xor_out,
table_idx_width=opt.tbl_idx_width)
init = crc.nondirect_init
elif opt.algorithm == opt.algo_bit_by_bit_fast:
if opt.xor_in is None:
return None
init = opt.xor_in
elif opt.algorithm == opt.algo_table_driven:
if opt.reflect_in is None or opt.xor_in is None or opt.width is None:
return None
if opt.poly is None:
poly = 0
else:
poly = opt.poly
crc = Crc(width=opt.width,
poly=poly,
reflect_in=opt.reflect_in,
xor_in=opt.xor_in,
reflect_out=opt.reflect_out,
xor_out=opt.xor_out,
table_idx_width=opt.tbl_idx_width)
if opt.reflect_in:
init = crc.reflect(crc.direct_init, opt.width)
else:
init = crc.direct_init
else:
init = 0
return _pretty_hex(init, opt.width)
def _get_init_value(opt):
"""
Return the init value of a C implementation, according to the selected
algorithm and to the given options.
If no default option is given for a given parameter, value in the cfg_t
structure must be used.
"""
if opt.algorithm == opt.algo_bit_by_bit:
if opt.xor_in is None or opt.width is None or opt.poly is None:
return None
crc = Crc(
width=opt.width, poly=opt.poly,
reflect_in=opt.reflect_in, xor_in=opt.xor_in,
reflect_out=opt.reflect_out, xor_out=opt.xor_out,
table_idx_width=opt.tbl_idx_width)
init = crc.nondirect_init
elif opt.algorithm == opt.algo_bit_by_bit_fast:
if opt.xor_in is None:
return None
init = opt.xor_in
elif opt.algorithm == opt.algo_table_driven:
if opt.reflect_in is None or opt.xor_in is None or opt.width is None:
return None
if opt.poly is None:
poly = 0
else:
poly = opt.poly
crc = Crc(
width=opt.width, poly=poly,
reflect_in=opt.reflect_in, xor_in=opt.xor_in,
reflect_out=opt.reflect_out, xor_out=opt.xor_out,
table_idx_width=opt.tbl_idx_width)
if opt.reflect_in:
init = crc.reflect(crc.direct_init, opt.width)
else:
init = crc.direct_init
else:
init = 0
return _pretty_hex(init, opt.width)