def dec_to_bcd_8421(num):
"""Convert a decimal to binary, and decompress into Binary Coded Decimal.
Adds trailing bits to the left to enforce a 4-bit "nibble" on all digits.
Uses 8421 notation [see wikipedia.org/wiki/Binary-coded_decimal]"""
bcd, binary, decimals = '', '', ''
for digit in str(num):
binval = encoders.dec_to_bin(int(digit))
binary += '{}{}'.format(binval, ' ' * (4 - len(binval) + 1))
if len(binval) < 4:
binval = binval.zfill(4)
bcd += '{} '.format(binval)
decimals += digit + (' ' * 4)
_show_bcd(num, decimals, binary, bcd)
return bcd
def dec_to_bcd_excess3(num, bias=3):
"""Converts a binary to Binary Coded Decimal, then converts again to
excess-3 BCD, which has a 'bit bias' of `bias`, where bits are
shifted by the given bias. See wikipedia.org/wiki/Excess-3 for more."""
bcd, binary, decimals = '', '', ''
for digit in str(num):
binval = encoders.dec_to_bin(int(digit))
binval = BaseDataType.add(str(binval), bias)
binary += '{}{}'.format(binval, ' ' * (4 - len(binval) + 1))
if len(binval) < 4:
binval = binval.zfill(4)
bcd += '{} '.format(binval)
decimals += digit + (' ' * 4)
_show_bcd(num, decimals, binary, bcd)
return bcd
def get_networkid(self, ip):
"""Network ID is comprised of Network Destination and Netmask,
using CIDR notation. https://www.youtube.com/watch?v=t5xYI0jzOf4
"""
entry = self[ip]
mask = entry['network_mask']
offset = 0
# Add the octets as binary, then get the number of most significant
# bits and add those to the end, to get the final CIDR encoded number.
for octet in mask.split('.'):
if octet == '255':
offset += 8
elif octet != '0':
bits = encoders.dec_to_bin(int(octet))[0:4]
for bit in bits:
if bit == '1':
offset += 1
return '{}/{}'.format(entry['destination'], offset)
def twos_complement(binary):
"""Conversion algorithm from
cs.cornell.edu/~tomf/notes/cps104/twoscomp.html#twotwo"""
old = binary
binary = ones_complement(binary)
ones = binary
binary = BaseDataType.increment(''.join(binary))
if DEBUG:
print('Complements: one: {}, two: {}, (original: {})'.format(
''.join(ones), binary, ''.join(old)))
dec = bin_to_dec(binary)
sign, res = ('neg', -dec) if list(binary)[0] == '1' else (
'pos',
dec,
)
res_bin = dec_to_bin(res)
if DEBUG:
print('Final decimal is {}: {} ({})'.format(sign, res, res_bin))
return res_bin
