130 lines
2.9 KiB
Python
130 lines
2.9 KiB
Python
#!/usr/bin/env python
|
|
#
|
|
# Copyright (c) 2008-2012 WiredTiger, Inc.
|
|
# All rights reserved.
|
|
#
|
|
# See the file LICENSE for redistribution information.
|
|
#
|
|
# WiredTiger variable-length packing and unpacking functions
|
|
|
|
from intpacking import pack_int, unpack_int
|
|
|
|
def __get_type(fmt):
|
|
if not fmt:
|
|
return None, fmt
|
|
# Variable-sized encoding is the default (and only supported format in v1)
|
|
if fmt[0] in '.@<>':
|
|
tfmt = fmt[0]
|
|
fmt = fmt[1:]
|
|
else:
|
|
tfmt = '.'
|
|
return tfmt, fmt
|
|
|
|
def unpack(fmt, s):
|
|
tfmt, fmt = __get_type(fmt)
|
|
if not fmt:
|
|
return ()
|
|
if tfmt != '.':
|
|
raise ValueError('Only variable-length encoding is currently supported')
|
|
result = []
|
|
havesize = size = 0
|
|
for offset, f in enumerate(fmt):
|
|
if f.isdigit():
|
|
size = (size * 10) + int(f)
|
|
havesize = 1
|
|
continue
|
|
elif f == 'x':
|
|
if not havesize:
|
|
size = 1
|
|
s = s[size:]
|
|
# Note: no value, don't increment i
|
|
elif f in 'Ssu':
|
|
if not havesize:
|
|
if f == 's':
|
|
size = 1
|
|
elif f == 'S':
|
|
size = s.find('\0')
|
|
elif f == 'u':
|
|
if offset == len(fmt) - 1:
|
|
size = len(s)
|
|
else:
|
|
size, s = unpack_int(s)
|
|
result.append(s[:size])
|
|
if f == 'S' and not havesize:
|
|
size += 1
|
|
s = s[size:]
|
|
elif f in 't':
|
|
# bit type, size is number of bits
|
|
if not havesize:
|
|
size = 1
|
|
result.append(ord(s[0:1]))
|
|
s = s[1:]
|
|
else:
|
|
# integral type
|
|
if not havesize:
|
|
size = 1
|
|
for j in xrange(size):
|
|
v, s = unpack_int(s)
|
|
result.append(v)
|
|
havesize = size = 0
|
|
return result
|
|
|
|
def pack(fmt, *values):
|
|
tfmt, fmt = __get_type(fmt)
|
|
if not fmt:
|
|
return ()
|
|
if tfmt != '.':
|
|
raise ValueError('Only variable-length encoding is currently supported')
|
|
result = ''
|
|
havesize = i = size = 0
|
|
for offset, f in enumerate(fmt):
|
|
if f.isdigit():
|
|
size = (size * 10) + int(f)
|
|
havesize = 1
|
|
continue
|
|
elif f == 'x':
|
|
if not havesize:
|
|
result += '\0'
|
|
else:
|
|
result += '\0' * size
|
|
# Note: no value, don't increment i
|
|
elif f in 'Ssu':
|
|
if f == 'S' and '\0' in values[i]:
|
|
l = values[i].find('\0')
|
|
else:
|
|
l = len(values[i])
|
|
if havesize:
|
|
if l > size:
|
|
l = size
|
|
elif f == 's':
|
|
havesize = size = 1
|
|
elif f == 'u' and offset != len(fmt) - 1:
|
|
result += pack_int(l)
|
|
result += values[i][:l]
|
|
if f == 'S' and not havesize:
|
|
result += '\0'
|
|
elif size > l:
|
|
result += '\0' * (size - l)
|
|
i += 1
|
|
elif f in 't':
|
|
# bit type, size is number of bits
|
|
if not havesize:
|
|
size = 1
|
|
if size > 8:
|
|
raise ValueError("bit count cannot be greater than 8 for 't' encoding")
|
|
mask = (1 << size) - 1
|
|
val = values[i]
|
|
if (mask & val) != val:
|
|
raise ValueError("value out of range for 't' encoding")
|
|
result += chr(val)
|
|
i += 1
|
|
else:
|
|
# integral type
|
|
if not havesize:
|
|
size = 1
|
|
for j in xrange(size):
|
|
result += pack_int(values[i])
|
|
i += 1
|
|
havesize = size = 0
|
|
return result
|