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)