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
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
|
"""
Pure python implementation of Postgres hashes
>>> import skytools.hashtext
>>> data = 'HypficUjFitraxlumCitcemkiOkIkthi'
>>> p = [hashtext_old_py(data[:l]) for l in range(1, len(data)+1)]
>>> c = [hashtext_old(data[:l]) for l in range(1, len(data)+1)]
>>> assert p == c, '%s <> %s' % (p, c)
>>> p = [hashtext_new_py(data[:l]) for l in range(1, len(data)+1)]
>>> c = [hashtext_new(data[:l]) for l in range(1, len(data)+1)]
>>> assert p == c, '%s <> %s' % (p, c)
"""
import struct
__all__ = [
"hashtext_old_py", "hashtext_new_py",
"hashtext_old", "hashtext_new"
]
padding = '\0' * 12
def uint32(x):
"""python does not have 32 bit integer so we need this hack to produce uint32 after bit operations"""
return x & 0xffffffff
#
# Old Postgres hashtext()
#
fmt_old = struct.Struct("<LLL")
def mix_old(a,b,c):
c = uint32(c)
a -= b; a -= c; a = uint32(a ^ (c>>13))
b -= c; b -= a; b = uint32(b ^ (a<<8))
c -= a; c -= b; c = uint32(c ^ (b>>13))
a -= b; a -= c; a = uint32(a ^ (c>>12))
b -= c; b -= a; b = uint32(b ^ (a<<16))
c -= a; c -= b; c = uint32(c ^ (b>>5))
a -= b; a -= c; a = uint32(a ^ (c>>3))
b -= c; b -= a; b = uint32(b ^ (a<<10))
c -= a; c -= b; c = uint32(c ^ (b>>15))
return a, b, c
def hashtext_old_py(k):
keylen = lenpos = len(k)
p = 0
a = b = 0x9e3779b9
c = 3923095
# handle most of the key
while lenpos >= 12:
a2, b2, c2 = fmt_old.unpack_from(k, p)
a, b, c = mix_old(a + a2, b + b2, c + c2)
p += 12;
lenpos -= 12;
# handle the last 11 bytes
a2, b2, c2 = fmt_old.unpack_from(k[p:] + padding, 0)
# the lowest byte of c is reserved for the length
c += keylen;
c2 = c2 << 8
a, b, c = mix_old(a + a2, b + b2, c + c2)
# convert to signed int
if (c & 0x80000000):
c = -0x100000000 + c
return c
#
# New Postgres hashtext()
#
fmt_new = struct.Struct("=LLL")
def rol32(x,k):
return (((x)<<(k)) | (uint32(x)>>(32-(k))))
def mix_new(a,b,c):
a -= c; a ^= rol32(c, 4); c += b
b -= a; b ^= rol32(a, 6); a += c
c -= b; c ^= rol32(b, 8); b += a
a -= c; a ^= rol32(c,16); c += b
b -= a; b ^= rol32(a,19); a += c
c -= b; c ^= rol32(b, 4); b += a
return uint32(a), uint32(b), uint32(c)
def final_new(a,b,c):
c ^= b; c -= rol32(b,14)
a ^= c; a -= rol32(c,11)
b ^= a; b -= rol32(a,25)
c ^= b; c -= rol32(b,16)
a ^= c; a -= rol32(c, 4)
b ^= a; b -= rol32(a,14)
c ^= b; c -= rol32(b,24)
return uint32(a), uint32(b), uint32(c)
def hashtext_new_py(k):
keylen = lenpos = len(k)
p = 0
a = b = c = 0x9e3779b9 + keylen + 3923095
# handle most of the key
while lenpos >= 12:
a2, b2, c2 = fmt_new.unpack_from(k, p)
a, b, c = mix_new(a + a2, b + b2, c + c2)
p += 12;
lenpos -= 12;
# handle the last 11 bytes
a2, b2, c2 = fmt_new.unpack_from(k[p:] + padding, 0)
# the lowest byte of c is reserved
c2 = c2 << 8
a, b, c = final_new(a + a2, b + b2, c + c2)
# convert to signed int
if (c & 0x80000000):
c = -0x100000000 + c
return c
try:
from skytools.hashtext import hashtext_old, hashtext_new
except ImportError:
hashtext_old = hashtext_old_py
hashtext_new = hashtext_new_py
# run doctest
if __name__ == '__main__':
import doctest
doctest.testmod()
|
