1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
from .errors import DescriptorError
def polymod(c: int, val: int) -> int:
c0 = c >> 35
c = ((c & 0x7FFFFFFFF) << 5) ^ val
if c0 & 1:
c ^= 0xF5DEE51989
if c0 & 2:
c ^= 0xA9FDCA3312
if c0 & 4:
c ^= 0x1BAB10E32D
if c0 & 8:
c ^= 0x3706B1677A
if c0 & 16:
c ^= 0x644D626FFD
return c
def checksum(desc: str) -> str:
"""Calculate checksum of desciptor string"""
INPUT_CHARSET = (
"0123456789()[],'/*abcdefgh@:$%{}IJKLMNOPQRSTUVW"
'XYZ&+-.;<=>?!^_|~ijklmnopqrstuvwxyzABCDEFGH`#"\\ '
)
CHECKSUM_CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
c = 1
cls = 0
clscount = 0
for ch in desc:
pos = INPUT_CHARSET.find(ch)
if pos == -1:
raise DescriptorError("Invalid character '%s' in the input string" % ch)
c = polymod(c, pos & 31)
cls = cls * 3 + (pos >> 5)
clscount += 1
if clscount == 3:
c = polymod(c, cls)
cls = 0
clscount = 0
if clscount > 0:
c = polymod(c, cls)
for j in range(0, 8):
c = polymod(c, 0)
c ^= 1
ret = [CHECKSUM_CHARSET[(c >> (5 * (7 - j))) & 31] for j in range(0, 8)]
return "".join(ret)
def add_checksum(desc: str) -> str:
"""Add checksum to descriptor string"""
if "#" in desc:
desc = desc.split("#")[0]
return desc + "#" + checksum(desc)
|
