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1 | # xref unique ID hash calculation |
2 | # | |
3 | # Copyright (C) 2020 David Lamparter for NetDEF, Inc. | |
4 | # | |
5 | # This program is free software; you can redistribute it and/or modify it | |
6 | # under the terms of the GNU General Public License as published by the Free | |
7 | # Software Foundation; either version 2 of the License, or (at your option) | |
8 | # any later version. | |
9 | # | |
10 | # This program is distributed in the hope that it will be useful, but WITHOUT | |
11 | # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
12 | # FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for | |
13 | # more details. | |
14 | # | |
15 | # You should have received a copy of the GNU General Public License along | |
16 | # with this program; see the file COPYING; if not, write to the Free Software | |
17 | # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA | |
18 | ||
19 | import struct | |
20 | from hashlib import sha256 | |
21 | ||
00f0c399 DL |
22 | |
23 | def bititer(data, bits, startbit=True): | |
24 | """ | |
36a8fdfd DL |
25 | just iterate the individual bits out from a bytes object |
26 | ||
27 | if startbit is True, an '1' bit is inserted at the very beginning | |
28 | goes <bits> at a time, starts at LSB. | |
00f0c399 | 29 | """ |
36a8fdfd DL |
30 | bitavail, v = 0, 0 |
31 | if startbit and len(data) > 0: | |
32 | v = data.pop(0) | |
33 | yield (v & ((1 << bits) - 1)) | (1 << (bits - 1)) | |
34 | bitavail = 9 - bits | |
35 | v >>= bits - 1 | |
36 | ||
37 | while len(data) > 0: | |
38 | while bitavail < bits: | |
39 | v |= data.pop(0) << bitavail | |
40 | bitavail += 8 | |
41 | yield v & ((1 << bits) - 1) | |
42 | bitavail -= bits | |
43 | v >>= bits | |
44 | ||
00f0c399 | 45 | |
36a8fdfd | 46 | def base32c(data): |
00f0c399 | 47 | """ |
36a8fdfd | 48 | Crockford base32 with extra dashes |
00f0c399 | 49 | """ |
36a8fdfd | 50 | chs = "0123456789ABCDEFGHJKMNPQRSTVWXYZ" |
00f0c399 | 51 | o = "" |
36a8fdfd DL |
52 | if type(data) == str: |
53 | data = [ord(v) for v in data] | |
54 | else: | |
55 | data = list(data) | |
56 | for i, bits in enumerate(bititer(data, 5)): | |
57 | if i == 5: | |
00f0c399 | 58 | o = o + "-" |
36a8fdfd DL |
59 | elif i == 10: |
60 | break | |
61 | o = o + chs[bits] | |
62 | return o | |
63 | ||
00f0c399 | 64 | |
36a8fdfd | 65 | def uidhash(filename, hashstr, hashu32a, hashu32b): |
00f0c399 | 66 | """ |
36a8fdfd | 67 | xref Unique ID hash used in FRRouting |
00f0c399 DL |
68 | """ |
69 | filename = "/".join(filename.rsplit("/")[-2:]) | |
36a8fdfd | 70 | |
00f0c399 DL |
71 | hdata = filename.encode("UTF-8") + hashstr.encode("UTF-8") |
72 | hdata += struct.pack(">II", hashu32a, hashu32b) | |
36a8fdfd DL |
73 | i = sha256(hdata).digest() |
74 | return base32c(i) |