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- #!/usr/bin/env python
- '''
- $Id: tzfile.py,v 1.8 2004/06/03 00:15:24 zenzen Exp $
- '''
-
- from datetime import datetime
- from struct import unpack, calcsize
-
- from pytz.tzinfo import StaticTzInfo, DstTzInfo, memorized_ttinfo
- from pytz.tzinfo import memorized_datetime, memorized_timedelta
-
-
- def _byte_string(s):
- """Cast a string or byte string to an ASCII byte string."""
- return s.encode('ASCII')
-
- _NULL = _byte_string('\0')
-
-
- def _std_string(s):
- """Cast a string or byte string to an ASCII string."""
- return str(s.decode('ASCII'))
-
-
- def build_tzinfo(zone, fp):
- head_fmt = '>4s c 15x 6l'
- head_size = calcsize(head_fmt)
- (magic, format, ttisgmtcnt, ttisstdcnt, leapcnt, timecnt,
- typecnt, charcnt) = unpack(head_fmt, fp.read(head_size))
-
- # Make sure it is a tzfile(5) file
- assert magic == _byte_string('TZif'), 'Got magic %s' % repr(magic)
-
- # Read out the transition times, localtime indices and ttinfo structures.
- data_fmt = '>%(timecnt)dl %(timecnt)dB %(ttinfo)s %(charcnt)ds' % dict(
- timecnt=timecnt, ttinfo='lBB' * typecnt, charcnt=charcnt)
- data_size = calcsize(data_fmt)
- data = unpack(data_fmt, fp.read(data_size))
-
- # make sure we unpacked the right number of values
- assert len(data) == 2 * timecnt + 3 * typecnt + 1
- transitions = [memorized_datetime(trans)
- for trans in data[:timecnt]]
- lindexes = list(data[timecnt:2 * timecnt])
- ttinfo_raw = data[2 * timecnt:-1]
- tznames_raw = data[-1]
- del data
-
- # Process ttinfo into separate structs
- ttinfo = []
- tznames = {}
- i = 0
- while i < len(ttinfo_raw):
- # have we looked up this timezone name yet?
- tzname_offset = ttinfo_raw[i + 2]
- if tzname_offset not in tznames:
- nul = tznames_raw.find(_NULL, tzname_offset)
- if nul < 0:
- nul = len(tznames_raw)
- tznames[tzname_offset] = _std_string(
- tznames_raw[tzname_offset:nul])
- ttinfo.append((ttinfo_raw[i],
- bool(ttinfo_raw[i + 1]),
- tznames[tzname_offset]))
- i += 3
-
- # Now build the timezone object
- if len(ttinfo) == 1 or len(transitions) == 0:
- ttinfo[0][0], ttinfo[0][2]
- cls = type(zone, (StaticTzInfo,), dict(
- zone=zone,
- _utcoffset=memorized_timedelta(ttinfo[0][0]),
- _tzname=ttinfo[0][2]))
- else:
- # Early dates use the first standard time ttinfo
- i = 0
- while ttinfo[i][1]:
- i += 1
- if ttinfo[i] == ttinfo[lindexes[0]]:
- transitions[0] = datetime.min
- else:
- transitions.insert(0, datetime.min)
- lindexes.insert(0, i)
-
- # calculate transition info
- transition_info = []
- for i in range(len(transitions)):
- inf = ttinfo[lindexes[i]]
- utcoffset = inf[0]
- if not inf[1]:
- dst = 0
- else:
- for j in range(i - 1, -1, -1):
- prev_inf = ttinfo[lindexes[j]]
- if not prev_inf[1]:
- break
- dst = inf[0] - prev_inf[0] # dst offset
-
- # Bad dst? Look further. DST > 24 hours happens when
- # a timzone has moved across the international dateline.
- if dst <= 0 or dst > 3600 * 3:
- for j in range(i + 1, len(transitions)):
- stdinf = ttinfo[lindexes[j]]
- if not stdinf[1]:
- dst = inf[0] - stdinf[0]
- if dst > 0:
- break # Found a useful std time.
-
- tzname = inf[2]
-
- # Round utcoffset and dst to the nearest minute or the
- # datetime library will complain. Conversions to these timezones
- # might be up to plus or minus 30 seconds out, but it is
- # the best we can do.
- utcoffset = int((utcoffset + 30) // 60) * 60
- dst = int((dst + 30) // 60) * 60
- transition_info.append(memorized_ttinfo(utcoffset, dst, tzname))
-
- cls = type(zone, (DstTzInfo,), dict(
- zone=zone,
- _utc_transition_times=transitions,
- _transition_info=transition_info))
-
- return cls()
-
- if __name__ == '__main__':
- import os.path
- from pprint import pprint
- base = os.path.join(os.path.dirname(__file__), 'zoneinfo')
- tz = build_tzinfo('Australia/Melbourne',
- open(os.path.join(base, 'Australia', 'Melbourne'), 'rb'))
- tz = build_tzinfo('US/Eastern',
- open(os.path.join(base, 'US', 'Eastern'), 'rb'))
- pprint(tz._utc_transition_times)
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