blob: 88135f1a70237611279a80ce57f89cc90f23547d (
plain)
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
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
|
import binascii
from ._crc32c import crc as crc32c_py
def encode_varint(value, write):
""" Encode an integer to a varint presentation. See
https://developers.google.com/protocol-buffers/docs/encoding?csw=1#varints
on how those can be produced.
Arguments:
value (int): Value to encode
write (function): Called per byte that needs to be writen
Returns:
int: Number of bytes written
"""
value = (value << 1) ^ (value >> 63)
if value <= 0x7f: # 1 byte
write(value)
return 1
if value <= 0x3fff: # 2 bytes
write(0x80 | (value & 0x7f))
write(value >> 7)
return 2
if value <= 0x1fffff: # 3 bytes
write(0x80 | (value & 0x7f))
write(0x80 | ((value >> 7) & 0x7f))
write(value >> 14)
return 3
if value <= 0xfffffff: # 4 bytes
write(0x80 | (value & 0x7f))
write(0x80 | ((value >> 7) & 0x7f))
write(0x80 | ((value >> 14) & 0x7f))
write(value >> 21)
return 4
if value <= 0x7ffffffff: # 5 bytes
write(0x80 | (value & 0x7f))
write(0x80 | ((value >> 7) & 0x7f))
write(0x80 | ((value >> 14) & 0x7f))
write(0x80 | ((value >> 21) & 0x7f))
write(value >> 28)
return 5
else:
# Return to general algorithm
bits = value & 0x7f
value >>= 7
i = 0
while value:
write(0x80 | bits)
bits = value & 0x7f
value >>= 7
i += 1
write(bits)
return i
def size_of_varint(value):
""" Number of bytes needed to encode an integer in variable-length format.
"""
value = (value << 1) ^ (value >> 63)
if value <= 0x7f:
return 1
if value <= 0x3fff:
return 2
if value <= 0x1fffff:
return 3
if value <= 0xfffffff:
return 4
if value <= 0x7ffffffff:
return 5
if value <= 0x3ffffffffff:
return 6
if value <= 0x1ffffffffffff:
return 7
if value <= 0xffffffffffffff:
return 8
if value <= 0x7fffffffffffffff:
return 9
return 10
def decode_varint(buffer, pos=0):
""" Decode an integer from a varint presentation. See
https://developers.google.com/protocol-buffers/docs/encoding?csw=1#varints
on how those can be produced.
Arguments:
buffer (bytearry): buffer to read from.
pos (int): optional position to read from
Returns:
(int, int): Decoded int value and next read position
"""
result = buffer[pos]
if not (result & 0x81):
return (result >> 1), pos + 1
if not (result & 0x80):
return (result >> 1) ^ (~0), pos + 1
result &= 0x7f
pos += 1
shift = 7
while 1:
b = buffer[pos]
result |= ((b & 0x7f) << shift)
pos += 1
if not (b & 0x80):
return ((result >> 1) ^ -(result & 1), pos)
shift += 7
if shift >= 64:
raise ValueError("Out of int64 range")
def calc_crc32c(memview):
""" Calculate CRC-32C (Castagnoli) checksum over a memoryview of data
"""
crc = crc32c_py(memview)
return crc
def calc_crc32(memview):
""" Calculate simple CRC-32 checksum over a memoryview of data
"""
crc = binascii.crc32(memview) & 0xffffffff
return crc
|
