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
|
#!/usr/bin/env python
#
# Public Domain 2014-2016 MongoDB, Inc.
# Public Domain 2008-2014 WiredTiger, Inc.
#
# This is free and unencumbered software released into the public domain.
#
# Anyone is free to copy, modify, publish, use, compile, sell, or
# distribute this software, either in source code form or as a compiled
# binary, for any purpose, commercial or non-commercial, and by any
# means.
#
# In jurisdictions that recognize copyright laws, the author or authors
# of this software dedicate any and all copyright interest in the
# software to the public domain. We make this dedication for the benefit
# of the public at large and to the detriment of our heirs and
# successors. We intend this dedication to be an overt act of
# relinquishment in perpetuity of all present and future rights to this
# software under copyright law.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
# OTHER DEALINGS IN THE SOFTWARE.
#
# WiredTiger fixed-size packing and unpacking functions, using the Python
# struct library.
import struct
def __wt2struct(fmt):
if not fmt:
return None, fmt
# Big endian with no alignment is the default
if fmt[0] in '@=<>!':
tfmt = fmt[0]
fmt = fmt[1:]
else:
tfmt = '>'
return tfmt, fmt.replace('r', 'Q')
def unpack(fmt, s):
tfmt, fmt = __wt2struct(fmt)
if not fmt:
return ()
result = ()
pfmt = tfmt
sizebytes = 0
for offset, f in enumerate(fmt):
if f.isdigit():
sizebytes += 1
# With a fixed size, everything is encoded as a string
if f in 'Su' and sizebytes > 0:
f = 's'
if f not in 'Su':
pfmt += f
sizebytes = 0
continue
# We've hit something that needs special handling, split any fixed-size
# values we've already passed
if len(pfmt) > 1:
size = struct.calcsize(pfmt)
result += struct.unpack_from(pfmt, s)
s = s[size:]
if f == 'S':
l = s.find('\0')
result += (s[:l],)
s = s[l+1:]
if f == 'u':
if offset == len(fmt) - 1:
result += (s,)
else:
l = struct.unpack_from(tfmt + 'l', s)[0]
s = s[struct.calcsize(tfmt + 'l'):]
result += (s[:l],)
s = s[l:]
pfmt = tfmt
sizebytes = 0
if len(pfmt) > 1:
result += struct.unpack(pfmt, s)
return result
def pack(fmt, *values):
pfmt, fmt = __wt2struct(fmt)
if not fmt:
return ''
i = sizebytes = 0
for offset, f in enumerate(fmt):
if f == 'S':
# Note: this code is being careful about embedded NUL characters
if sizebytes == 0:
l = values[i].find('\0') + 1
if not l:
l = len(values[i]) + 1
pfmt += str(l)
sizebytes = len(str(l))
f = 's'
elif f == 'u':
if sizebytes == 0 and offset != len(fmt) - 1:
l = len(values[i])
pfmt += 'l' + str(l)
values = values[:i] + (l,) + values[i:]
sizebytes = len(str(l))
f = 's'
pfmt += f
if f.isdigit():
sizebytes += 1
continue
if f != 's' and sizebytes > 0:
i += int(pfmt[-sizebytes:])
else:
i += 1
sizebytes = 0
return struct.pack(pfmt, *values)
|