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"Implementation of tzinfo classes for use with datetime.datetime."
from __future__ import unicode_literals
import time
from datetime import timedelta, tzinfo
from django.utils.encoding import force_str, force_text, DEFAULT_LOCALE_ENCODING
# Python's doc say: "A tzinfo subclass must have an __init__() method that can
# be called with no arguments". FixedOffset and LocalTimezone don't honor this
# requirement. Defining __getinitargs__ is sufficient to fix copy/deepcopy as
# well as pickling/unpickling.
class FixedOffset(tzinfo):
"Fixed offset in minutes east from UTC."
def __init__(self, offset):
if isinstance(offset, timedelta):
self.__offset = offset
offset = self.__offset.seconds // 60
else:
self.__offset = timedelta(minutes=offset)
sign = '-' if offset < 0 else '+'
self.__name = "%s%02d%02d" % (sign, abs(offset) / 60., abs(offset) % 60)
def __repr__(self):
return self.__name
def __getinitargs__(self):
return self.__offset,
def utcoffset(self, dt):
return self.__offset
def tzname(self, dt):
return self.__name
def dst(self, dt):
return timedelta(0)
# This implementation is used for display purposes. It uses an approximation
# for DST computations on dates >= 2038.
# A similar implementation exists in django.utils.timezone. It's used for
# timezone support (when USE_TZ = True) and focuses on correctness.
class LocalTimezone(tzinfo):
"Proxy timezone information from time module."
def __init__(self, dt):
tzinfo.__init__(self)
self.__dt = dt
self._tzname = self.tzname(dt)
def __repr__(self):
return force_str(self._tzname)
def __getinitargs__(self):
return self.__dt,
def utcoffset(self, dt):
if self._isdst(dt):
return timedelta(seconds=-time.altzone)
else:
return timedelta(seconds=-time.timezone)
def dst(self, dt):
if self._isdst(dt):
return timedelta(seconds=-time.altzone) - timedelta(seconds=-time.timezone)
else:
return timedelta(0)
def tzname(self, dt):
is_dst = False if dt is None else self._isdst(dt)
try:
return force_text(time.tzname[is_dst], DEFAULT_LOCALE_ENCODING)
except UnicodeDecodeError:
return None
def _isdst(self, dt):
tt = (dt.year, dt.month, dt.day,
dt.hour, dt.minute, dt.second,
dt.weekday(), 0, 0)
try:
stamp = time.mktime(tt)
except (OverflowError, ValueError):
# 32 bit systems can't handle dates after Jan 2038, and certain
# systems can't handle dates before ~1901-12-01:
#
# >>> time.mktime((1900, 1, 13, 0, 0, 0, 0, 0, 0))
# OverflowError: mktime argument out of range
# >>> time.mktime((1850, 1, 13, 0, 0, 0, 0, 0, 0))
# ValueError: year out of range
#
# In this case, we fake the date, because we only care about the
# DST flag.
tt = (2037,) + tt[1:]
stamp = time.mktime(tt)
tt = time.localtime(stamp)
return tt.tm_isdst > 0
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