codekingpro/portable-devtools

1'''2$Id: tzfile.py,v 1.8 2004/06/03 00:15:24 zenzen Exp $3'''4 5from datetime import datetime6from struct import unpack, calcsize7 8from pytz.tzinfo import StaticTzInfo, DstTzInfo, memorized_ttinfo9from pytz.tzinfo import memorized_datetime, memorized_timedelta10 11 12def _byte_string(s):13    """Cast a string or byte string to an ASCII byte string."""14    return s.encode('ASCII')15 16_NULL = _byte_string('\0')17 18 19def _std_string(s):20    """Cast a string or byte string to an ASCII string."""21    return str(s.decode('ASCII'))22 23 24def build_tzinfo(zone, fp):25    head_fmt = '>4s c 15x 6l'26    head_size = calcsize(head_fmt)27    (magic, format, ttisgmtcnt, ttisstdcnt, leapcnt, timecnt,28        typecnt, charcnt) = unpack(head_fmt, fp.read(head_size))29 30    # Make sure it is a tzfile(5) file31    assert magic == _byte_string('TZif'), 'Got magic %s' % repr(magic)32 33    # Read out the transition times, localtime indices and ttinfo structures.34    data_fmt = '>%(timecnt)dl %(timecnt)dB %(ttinfo)s %(charcnt)ds' % dict(35        timecnt=timecnt, ttinfo='lBB' * typecnt, charcnt=charcnt)36    data_size = calcsize(data_fmt)37    data = unpack(data_fmt, fp.read(data_size))38 39    # make sure we unpacked the right number of values40    assert len(data) == 2 * timecnt + 3 * typecnt + 141    transitions = [memorized_datetime(trans)42                   for trans in data[:timecnt]]43    lindexes = list(data[timecnt:2 * timecnt])44    ttinfo_raw = data[2 * timecnt:-1]45    tznames_raw = data[-1]46    del data47 48    # Process ttinfo into separate structs49    ttinfo = []50    tznames = {}51    i = 052    while i < len(ttinfo_raw):53        # have we looked up this timezone name yet?54        tzname_offset = ttinfo_raw[i + 2]55        if tzname_offset not in tznames:56            nul = tznames_raw.find(_NULL, tzname_offset)57            if nul < 0:58                nul = len(tznames_raw)59            tznames[tzname_offset] = _std_string(60                tznames_raw[tzname_offset:nul])61        ttinfo.append((ttinfo_raw[i],62                       bool(ttinfo_raw[i + 1]),63                       tznames[tzname_offset]))64        i += 365 66    # Now build the timezone object67    if len(ttinfo) == 1 or len(transitions) == 0:68        ttinfo[0][0], ttinfo[0][2]69        cls = type(zone, (StaticTzInfo,), dict(70            zone=zone,71            _utcoffset=memorized_timedelta(ttinfo[0][0]),72            _tzname=ttinfo[0][2]))73    else:74        # Early dates use the first standard time ttinfo75        i = 076        while ttinfo[i][1]:77            i += 178        if ttinfo[i] == ttinfo[lindexes[0]]:79            transitions[0] = datetime.min80        else:81            transitions.insert(0, datetime.min)82            lindexes.insert(0, i)83 84        # calculate transition info85        transition_info = []86        for i in range(len(transitions)):87            inf = ttinfo[lindexes[i]]88            utcoffset = inf[0]89            if not inf[1]:90                dst = 091            else:92                for j in range(i - 1, -1, -1):93                    prev_inf = ttinfo[lindexes[j]]94                    if not prev_inf[1]:95                        break96                dst = inf[0] - prev_inf[0]  # dst offset97 98                # Bad dst? Look further. DST > 24 hours happens when99                # a timzone has moved across the international dateline.100                if dst <= 0 or dst > 3600 * 3:101                    for j in range(i + 1, len(transitions)):102                        stdinf = ttinfo[lindexes[j]]103                        if not stdinf[1]:104                            dst = inf[0] - stdinf[0]105                            if dst > 0:106                                break  # Found a useful std time.107 108            tzname = inf[2]109 110            # Round utcoffset and dst to the nearest minute or the111            # datetime library will complain. Conversions to these timezones112            # might be up to plus or minus 30 seconds out, but it is113            # the best we can do.114            utcoffset = int((utcoffset + 30) // 60) * 60115            dst = int((dst + 30) // 60) * 60116            transition_info.append(memorized_ttinfo(utcoffset, dst, tzname))117 118        cls = type(zone, (DstTzInfo,), dict(119            zone=zone,120            _utc_transition_times=transitions,121            _transition_info=transition_info))122 123    return cls()124 125if __name__ == '__main__':126    import os.path127    from pprint import pprint128    base = os.path.join(os.path.dirname(__file__), 'zoneinfo')129    tz = build_tzinfo('Australia/Melbourne',130                      open(os.path.join(base, 'Australia', 'Melbourne'), 'rb'))131    tz = build_tzinfo('US/Eastern',132                      open(os.path.join(base, 'US', 'Eastern'), 'rb'))133    pprint(tz._utc_transition_times)134