1  import sys
       2  import os
       3  import struct
       4  from array import array
       5  from collections import namedtuple
       6  from datetime import datetime
       7  
       8  ttinfo = namedtuple('ttinfo', ['tt_gmtoff', 'tt_isdst', 'tt_abbrind'])
       9  
      10  class ESC[4;38;5;81mTZInfo:
      11      def __init__(self, transitions, type_indices, ttis, abbrs):
      12          self.transitions = transitions
      13          self.type_indices = type_indices
      14          self.ttis = ttis
      15          self.abbrs = abbrs
      16  
      17      @classmethod
      18      def fromfile(cls, fileobj):
      19          if fileobj.read(4).decode() != "TZif":
      20              raise ValueError("not a zoneinfo file")
      21          fileobj.seek(20)
      22          header = fileobj.read(24)
      23          tzh = (tzh_ttisgmtcnt, tzh_ttisstdcnt, tzh_leapcnt,
      24                 tzh_timecnt, tzh_typecnt, tzh_charcnt) = struct.unpack(">6l", header)
      25          transitions = array('i')
      26          transitions.fromfile(fileobj, tzh_timecnt)
      27          if sys.byteorder != 'big':
      28              transitions.byteswap()
      29  
      30          type_indices = array('B')
      31          type_indices.fromfile(fileobj, tzh_timecnt)
      32  
      33          ttis = []
      34          for i in range(tzh_typecnt):
      35              ttis.append(ttinfo._make(struct.unpack(">lbb", fileobj.read(6))))
      36  
      37          abbrs = fileobj.read(tzh_charcnt)
      38  
      39          self = cls(transitions, type_indices, ttis, abbrs)
      40          self.tzh = tzh
      41  
      42          return self
      43  
      44      def dump(self, stream, start=None, end=None):
      45          for j, (trans, i) in enumerate(zip(self.transitions, self.type_indices)):
      46              utc = datetime.utcfromtimestamp(trans)
      47              tti = self.ttis[i]
      48              lmt = datetime.utcfromtimestamp(trans + tti.tt_gmtoff)
      49              abbrind = tti.tt_abbrind
      50              abbr = self.abbrs[abbrind:self.abbrs.find(0, abbrind)].decode()
      51              if j > 0:
      52                  prev_tti = self.ttis[self.type_indices[j - 1]]
      53                  shift = " %+g" % ((tti.tt_gmtoff - prev_tti.tt_gmtoff) / 3600)
      54              else:
      55                  shift = ''
      56              print("%s UTC = %s %-5s isdst=%d" % (utc, lmt, abbr, tti[1]) + shift, file=stream)
      57  
      58      @classmethod
      59      def zonelist(cls, zonedir='/usr/share/zoneinfo'):
      60          zones = []
      61          for root, _, files in os.walk(zonedir):
      62              for f in files:
      63                  p = os.path.join(root, f)
      64                  with open(p, 'rb') as o:
      65                      magic =  o.read(4)
      66                  if magic == b'TZif':
      67                      zones.append(p[len(zonedir) + 1:])
      68          return zones
      69  
      70  if __name__ == '__main__':
      71      if len(sys.argv) < 2:
      72          zones = TZInfo.zonelist()
      73          for z in zones:
      74              print(z)
      75          sys.exit()
      76      filepath = sys.argv[1]
      77      if not filepath.startswith('/'):
      78          filepath = os.path.join('/usr/share/zoneinfo', filepath)
      79      with open(filepath, 'rb') as fileobj:
      80          tzi = TZInfo.fromfile(fileobj)
      81      tzi.dump(sys.stdout)