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import sys
import os
import struct
from array import array
from collections import namedtuple
from datetime import datetime, timedelta
ttinfo = namedtuple('ttinfo', ['tt_gmtoff', 'tt_isdst', 'tt_abbrind'])
class TZInfo:
def __init__(self, transitions, type_indices, ttis, abbrs):
self.transitions = transitions
self.type_indices = type_indices
self.ttis = ttis
self.abbrs = abbrs
@classmethod
def fromfile(cls, fileobj):
if fileobj.read(4).decode() != "TZif":
raise ValueError("not a zoneinfo file")
fileobj.seek(20)
header = fileobj.read(24)
tzh = (tzh_ttisgmtcnt, tzh_ttisstdcnt, tzh_leapcnt,
tzh_timecnt, tzh_typecnt, tzh_charcnt) = struct.unpack(">6l", header)
transitions = array('i')
transitions.fromfile(fileobj, tzh_timecnt)
if sys.byteorder != 'big':
transitions.byteswap()
type_indices = array('B')
type_indices.fromfile(fileobj, tzh_timecnt)
ttis = []
for i in range(tzh_typecnt):
ttis.append(ttinfo._make(struct.unpack(">lbb", fileobj.read(6))))
abbrs = fileobj.read(tzh_charcnt)
self = cls(transitions, type_indices, ttis, abbrs)
self.tzh = tzh
return self
def dump(self, stream, start=None, end=None):
for j, (trans, i) in enumerate(zip(self.transitions, self.type_indices)):
utc = datetime.utcfromtimestamp(trans)
tti = self.ttis[i]
lmt = datetime.utcfromtimestamp(trans + tti.tt_gmtoff)
abbrind = tti.tt_abbrind
abbr = self.abbrs[abbrind:self.abbrs.find(0, abbrind)].decode()
if j > 0:
prev_tti = self.ttis[self.type_indices[j - 1]]
shift = " %+g" % ((tti.tt_gmtoff - prev_tti.tt_gmtoff) / 3600)
else:
shift = ''
print("%s UTC = %s %-5s isdst=%d" % (utc, lmt, abbr, tti[1]) + shift, file=stream)
@classmethod
def zonelist(cls, zonedir='/usr/share/zoneinfo'):
zones = []
for root, _, files in os.walk(zonedir):
for f in files:
p = os.path.join(root, f)
with open(p, 'rb') as o:
magic = o.read(4)
if magic == b'TZif':
zones.append(p[len(zonedir) + 1:])
return zones
if __name__ == '__main__':
if len(sys.argv) < 2:
zones = TZInfo.zonelist()
for z in zones:
print(z)
sys.exit()
filepath = sys.argv[1]
if not filepath.startswith('/'):
filepath = os.path.join('/usr/share/zoneinfo', filepath)
with open(filepath, 'rb') as fileobj:
tzi = TZInfo.fromfile(fileobj)
tzi.dump(sys.stdout)
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