tz.py

Python的一个ORM,现在很火

        # Finally, there are tzh_ttisgmtcnt UTC/local
        # indicators, each stored as a one-byte value;
        # they tell whether the transition times associated
        # with local time types were specified as UTC or
        # local time, and are used when a time zone file
        # is used in handling POSIX-style time zone envi-
        # ronment variables.

        if ttisgmtcnt:
            isgmt = struct.unpack(">%db" % ttisgmtcnt,
                                  fileobj.read(ttisgmtcnt))

        # ** Everything has been read **

        # Build ttinfo list
        self._ttinfo_list = []
        for i in range(typecnt):
            gmtoff, isdst, abbrind =  ttinfo[i]
            # Round to full-minutes if that's not the case. Python's
            # datetime doesn't accept sub-minute timezones. Check
            # http://python.org/sf/1447945 for some information.
            gmtoff = (gmtoff+30)//60*60
            tti = _ttinfo()
            tti.offset = gmtoff
            tti.delta = datetime.timedelta(seconds=gmtoff)
            tti.isdst = isdst
            tti.abbr = abbr[abbrind:abbr.find('\x00', abbrind)]
            tti.isstd = (ttisstdcnt > i and isstd[i] != 0)
            tti.isgmt = (ttisgmtcnt > i and isgmt[i] != 0)
            self._ttinfo_list.append(tti)

        # Replace ttinfo indexes for ttinfo objects.
        trans_idx = []
        for idx in self._trans_idx:
            trans_idx.append(self._ttinfo_list[idx])
        self._trans_idx = tuple(trans_idx)

        # Set standard, dst, and before ttinfos. before will be
        # used when a given time is before any transitions,
        # and will be set to the first non-dst ttinfo, or to
        # the first dst, if all of them are dst.
        self._ttinfo_std = None
        self._ttinfo_dst = None
        self._ttinfo_before = None
        if self._ttinfo_list:
            if not self._trans_list:
                self._ttinfo_std = self._ttinfo_first = self._ttinfo_list[0]
            else:
                for i in range(timecnt-1,-1,-1):
                    tti = self._trans_idx[i]
                    if not self._ttinfo_std and not tti.isdst:
                        self._ttinfo_std = tti
                    elif not self._ttinfo_dst and tti.isdst:
                        self._ttinfo_dst = tti
                    if self._ttinfo_std and self._ttinfo_dst:
                        break
                else:
                    if self._ttinfo_dst and not self._ttinfo_std:
                        self._ttinfo_std = self._ttinfo_dst

                for tti in self._ttinfo_list:
                    if not tti.isdst:
                        self._ttinfo_before = tti
                        break
                else:
                    self._ttinfo_before = self._ttinfo_list[0]

        # Now fix transition times to become relative to wall time.
        #
        # I'm not sure about this. In my tests, the tz source file
        # is setup to wall time, and in the binary file isstd and
        # isgmt are off, so it should be in wall time. OTOH, it's
        # always in gmt time. Let me know if you have comments
        # about this.
        laststdoffset = 0
        self._trans_list = list(self._trans_list)
        for i in range(len(self._trans_list)):
            tti = self._trans_idx[i]
            if not tti.isdst:
                # This is std time.
                self._trans_list[i] += tti.offset
                laststdoffset = tti.offset
            else:
                # This is dst time. Convert to std.
                self._trans_list[i] += laststdoffset
        self._trans_list = tuple(self._trans_list)

    def _find_ttinfo(self, dt, laststd=0):
        timestamp = ((dt.toordinal() - EPOCHORDINAL) * 86400
                     + dt.hour * 3600
                     + dt.minute * 60
                     + dt.second)
        idx = 0
        for trans in self._trans_list:
            if timestamp < trans:
                break
            idx += 1
        else:
            return self._ttinfo_std
        if idx == 0:
            return self._ttinfo_before
        if laststd:
            while idx > 0:
                tti = self._trans_idx[idx-1]
                if not tti.isdst:
                    return tti
                idx -= 1
            else:
                return self._ttinfo_std
        else:
            return self._trans_idx[idx-1]

    def utcoffset(self, dt):
        if not self._ttinfo_std:
            return ZERO
        return self._find_ttinfo(dt).delta

    def dst(self, dt):
        if not self._ttinfo_dst:
            return ZERO
        tti = self._find_ttinfo(dt)
        if not tti.isdst:
            return ZERO

        # The documentation says that utcoffset()-dst() must
        # be constant for every dt.
        return self._find_ttinfo(dt, laststd=1).delta-tti.delta

        # An alternative for that would be:
        #
        # return self._ttinfo_dst.offset-self._ttinfo_std.offset
        #
        # However, this class stores historical changes in the
        # dst offset, so I belive that this wouldn't be the right
        # way to implement this.
        
    def tzname(self, dt):
        if not self._ttinfo_std:
            return None
        return self._find_ttinfo(dt).abbr

    def __eq__(self, other):
        if not isinstance(other, tzfile):
            return False
        return (self._trans_list == other._trans_list and
                self._trans_idx == other._trans_idx and
                self._ttinfo_list == other._ttinfo_list)

    def __ne__(self, other):
        return not self.__eq__(other)


    def __repr__(self):
        return "%s(%s)" % (self.__class__.__name__, `self._filename`)

    def __reduce__(self):
        if not os.path.isfile(self._filename):
            raise ValueError, "Unpickable %s class" % self.__class__.__name__
        return (self.__class__, (self._filename,))

class tzrange(datetime.tzinfo):

    def __init__(self, stdabbr, stdoffset=None,
                 dstabbr=None, dstoffset=None,
                 start=None, end=None):
        global relativedelta
        if not relativedelta:
            from dateutil import relativedelta
        self._std_abbr = stdabbr
        self._dst_abbr = dstabbr
        if stdoffset is not None:
            self._std_offset = datetime.timedelta(seconds=stdoffset)
        else:
            self._std_offset = ZERO
        if dstoffset is not None:
            self._dst_offset = datetime.timedelta(seconds=dstoffset)
        elif dstabbr and stdoffset is not None:
            self._dst_offset = self._std_offset+datetime.timedelta(hours=+1)
        else:
            self._dst_offset = ZERO
        if start is None:
            self._start_delta = relativedelta.relativedelta(
                    hours=+2, month=4, day=1, weekday=relativedelta.SU(+1))
        else:
            self._start_delta = start
        if end is None:
            self._end_delta = relativedelta.relativedelta(
                    hours=+1, month=10, day=31, weekday=relativedelta.SU(-1))
        else:
            self._end_delta = end

    def utcoffset(self, dt):
        if self._isdst(dt):
            return self._dst_offset
        else:
            return self._std_offset

    def dst(self, dt):
        if self._isdst(dt):
            return self._dst_offset-self._std_offset
        else:
            return ZERO

    def tzname(self, dt):
        if self._isdst(dt):
            return self._dst_abbr
        else:
            return self._std_abbr

    def _isdst(self, dt):
        if not self._start_delta:
            return False
        year = datetime.date(dt.year,1,1)
        start = year+self._start_delta
        end = year+self._end_delta
        dt = dt.replace(tzinfo=None)
        if start < end:
            return dt >= start and dt < end
        else:
            return dt >= start or dt < end

    def __eq__(self, other):
        if not isinstance(other, tzrange):
            return False
        return (self._std_abbr == other._std_abbr and
                self._dst_abbr == other._dst_abbr and
                self._std_offset == other._std_offset and
                self._dst_offset == other._dst_offset and
                self._start_delta == other._start_delta and
                self._end_delta == other._end_delta)

    def __ne__(self, other):
        return not self.__eq__(other)

    def __repr__(self):
        return "%s(...)" % self.__class__.__name__

    __reduce__ = object.__reduce__

class tzstr(tzrange):
    
    def __init__(self, s):
        global parser
        if not parser:
            from dateutil import parser
        self._s = s

        res = parser._parsetz(s)
        if res is None:
            raise ValueError, "unknown string format"

        # We must initialize it first, since _delta() needs
        # _std_offset and _dst_offset set. Use False in start/end
        # to avoid building it two times.
        tzrange.__init__(self, res.stdabbr, res.stdoffset,
                         res.dstabbr, res.dstoffset,
                         start=False, end=False)

        self._start_delta = self._delta(res.start)
        if self._start_delta:
            self._end_delta = self._delta(res.end, isend=1)

    def _delta(self, x, isend=0):
        kwargs = {}
        if x.month is not None:
            kwargs["month"] = x.month
            if x.weekday is not None:
                kwargs["weekday"] = relativedelta.weekday(x.weekday, x.week)
                if x.week > 0:
                    kwargs["day"] = 1
                else:
                    kwargs["day"] = 31
            elif x.day:
                kwargs["day"] = x.day
        elif x.yday is not None:
            kwargs["yearday"] = x.yday
        elif x.jyday is not None:
            kwargs["nlyearday"] = x.jyday
        if not kwargs:
            # Default is to start on first sunday of april, and end
            # on last sunday of october.
            if not isend:
                kwargs["month"] = 4
                kwargs["day"] = 1
                kwargs["weekday"] = relativedelta.SU(+1)
            else:
                kwargs["month"] = 10
                kwargs["day"] = 31
                kwargs["weekday"] = relativedelta.SU(-1)
        if x.time is not None:
            kwargs["seconds"] = x.time
        else:
            # Default is 2AM.
            kwargs["seconds"] = 7200
        if isend:
            # Convert to standard time, to follow the documented way
            # of working with the extra hour. See the documentation
            # of the tzinfo class.
            delta = self._dst_offset-self._std_offset
            kwargs["seconds"] -= delta.seconds+delta.days*86400
        return relativedelta.relativedelta(**kwargs)

    def __repr__(self):
        return "%s(%s)" % (self.__class__.__name__, `self._s`)

class _tzicalvtzcomp:
    def __init__(self, tzoffsetfrom, tzoffsetto, isdst,
                       tzname=None, rrule=None):
        self.tzoffsetfrom = datetime.timedelta(seconds=tzoffsetfrom)
        self.tzoffsetto = datetime.timedelta(seconds=tzoffsetto)
        self.tzoffsetdiff = self.tzoffsetto-self.tzoffsetfrom
        self.isdst = isdst
        self.tzname = tzname
        self.rrule = rrule