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#!/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
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