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# xref unique ID hash calculation
#
# Copyright (C) 2020 David Lamparter for NetDEF, Inc.
#
# This program is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the Free
# Software Foundation; either version 2 of the License, or (at your option)
# any later version.
#
# 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.
#
# You should have received a copy of the GNU General Public License along
# with this program; see the file COPYING; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
import struct
from hashlib import sha256
def bititer(data, bits, startbit = True):
'''
just iterate the individual bits out from a bytes object
if startbit is True, an '1' bit is inserted at the very beginning
goes <bits> at a time, starts at LSB.
'''
bitavail, v = 0, 0
if startbit and len(data) > 0:
v = data.pop(0)
yield (v & ((1 << bits) - 1)) | (1 << (bits - 1))
bitavail = 9 - bits
v >>= bits - 1
while len(data) > 0:
while bitavail < bits:
v |= data.pop(0) << bitavail
bitavail += 8
yield v & ((1 << bits) - 1)
bitavail -= bits
v >>= bits
def base32c(data):
'''
Crockford base32 with extra dashes
'''
chs = "0123456789ABCDEFGHJKMNPQRSTVWXYZ"
o = ''
if type(data) == str:
data = [ord(v) for v in data]
else:
data = list(data)
for i, bits in enumerate(bititer(data, 5)):
if i == 5:
o = o + '-'
elif i == 10:
break
o = o + chs[bits]
return o
def uidhash(filename, hashstr, hashu32a, hashu32b):
'''
xref Unique ID hash used in FRRouting
'''
filename = '/'.join(filename.rsplit('/')[-2:])
hdata = filename.encode('UTF-8') + hashstr.encode('UTF-8')
hdata += struct.pack('>II', hashu32a, hashu32b)
i = sha256(hdata).digest()
return base32c(i)
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