def crc(message,
polynom,
init=0,
in_reflection=False,
out_reflection=False,
out_xor=False):
root, reversed_, width = generate_root(polynom)
# we have to augment the string with 'width' bits
augmented_message = message + "\x00" * (width / 8)
#if no IN reflection is needed, we'll work in bit 7 first mode.
bit7_first = not in_reflection
bits = _bits.bits(augmented_message, bit7_first)
if width in MASK:
mask = MASK[width]
else:
mask = (1 << width) - 1
reg = init
#TODO: why ? check http://www.tty1.net/pycrc/#download
for i in xrange(width):
lowest_bit_set = (reg & 1) == 1
if lowest_bit_set:
reg ^= root
reg = (reg >> 1) | (lowest_bit_set << (width - 1))
for new_read_bit in bits:
highest_reg_bit_set = (((reg >> (width - 1)) & 1) == 1)
reg = ((reg << 1) & mask) | int(new_read_bit)
if highest_reg_bit_set:
reg ^= root
if out_reflection:
reg = _bits.reverse(reg, width)
if out_xor:
reg = ~reg
reg &= mask
return reg, width
def crc(message, polynom, init=0, in_reflection=False, out_reflection=False, out_xor=False):
root, reversed_, width = generate_root(polynom)
# we have to augment the string with 'width' bits
augmented_message = message + "\x00" * (width / 8)
#if no IN reflection is needed, we'll work in bit 7 first mode.
bit7_first = not in_reflection
bits = _bits.bits(augmented_message, bit7_first)
if width in MASK:
mask = MASK[width]
else:
mask = (1 << width) - 1
reg = init
#TODO: why ? check http://www.tty1.net/pycrc/#download
for i in xrange(width):
lowest_bit_set = (reg & 1) == 1
if lowest_bit_set:
reg ^= root
reg = (reg >> 1) | (lowest_bit_set << (width - 1))
for new_read_bit in bits:
highest_reg_bit_set = (((reg >> (width - 1)) & 1) == 1)
reg = ((reg << 1) & mask) | int(new_read_bit)
if highest_reg_bit_set:
reg ^= root
if out_reflection:
reg = _bits.reverse(reg, width)
if out_xor:
reg = ~reg
reg &= mask
return reg, width
#
#Kabopan - Readable Algorithms. Public Domain, 2007-2009
from kbp._bits import bits, reverse, compress, decompress
assert "".join(str(int(i)) for i in bits("AE")) == "01000001" + "01000101"
assert "".join(
str(int(i))
for i in bits("AE", bit7_first=False)) == "10000010" + "10100010"
assert reverse(10341313, 32) == 2211690752
assert reverse(reverse(10341313, 32), 32) == 10341313
c = compress(1)
c.write_bit(1)
assert c.getdata() == "\x80"
c = compress(2)
c.write_bit(1)
assert c.getdata() == "\x00\x80"
c = compress(2)
c.write_variablenumber(109)
assert c.getdata() == "`\xdf"
c = compress(2)
c.write_fixednumber(109, 9)
assert c.getdata() == '\x806'
#c = compress(2);c.write_bit(1);c.write_fixednumber(15, 5);c.write_variablenumber(2049);
#test = c.getdata()
#
#Kabopan - Readable Algorithms. Public Domain, 2007-2009
from kbp._bits import bits, reverse, compress, decompress
assert "".join(str(int(i)) for i in bits("AE")) == "01000001" + "01000101"
assert "".join(str(int(i)) for i in bits("AE", bit7_first=False)) == "10000010" + "10100010"
assert reverse(10341313, 32) == 2211690752
assert reverse(reverse(10341313, 32), 32) == 10341313
c = compress(1)
c.write_bit(1)
assert c.getdata() == "\x80"
c = compress(2)
c.write_bit(1)
assert c.getdata() == "\x00\x80"
c = compress(2)
c.write_variablenumber(109)
assert c.getdata() == "`\xdf"
c = compress(2)
c.write_fixednumber(109, 9)
assert c.getdata() == '\x806'
#c = compress(2);c.write_bit(1);c.write_fixednumber(15, 5);c.write_variablenumber(2049);
#test = c.getdata()
test = 'U\xbd`U'
d = decompress(test, 2)