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#!/usr/bin/env python
#
# Copyright (C) 2007 Lemur Consulting Ltd
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
r"""marshall.py: Marshal values into strings
"""
__docformat__ = "restructuredtext en"
import math
def _long_to_base256_array(value, length, flip):
result = []
for i in xrange(length):
n = value % 256
if flip: n = 255 - n
result.insert(0, chr(n))
value /= 256
return result
def float_to_string(value):
"""Marshall a floating point number to a string which sorts in the
appropriate manner.
"""
mantissa, exponent = math.frexp(value)
sign = '1'
if mantissa < 0:
mantissa = -mantissa
sign = '0'
# IEEE representation of doubles uses 11 bits for the exponent, with a bias
# of 1023. There's then another 52 bits in the mantissa, so we need to
# add 1075 to be sure that the exponent won't be negative.
# Even then, we check that the exponent isn't negative, and consider the
# value to be equal to zero if it is.
exponent += 1075
if exponent < 0: # Note - this can't happen on most architectures #pragma: no cover
exponent = 0
mantissa = 0
elif mantissa == 0:
exponent = 0
# IEEE representation of doubles uses 52 bits for the mantissa. Convert it
# to a 7 character string, and convert the exponent to a 2 character
# string.
mantissa = long(mantissa * (2**52))
digits = [sign]
digits.extend(_long_to_base256_array(exponent, 2, sign == '0'))
digits.extend(_long_to_base256_array(mantissa, 7, sign == '0'))
return ''.join(digits)
def date_to_string(date):
"""Marshall a date to a string which sorts in the appropriate manner.
"""
return '%04d%02d%02d' % (date.year, date.month, date.day)
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