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third_party/recipe_engine/third_party/dateutil/tz.py

Index: third_party/recipe_engine/third_party/dateutil/tz.py
diff --git a/third_party/recipe_engine/third_party/dateutil/tz.py b/third_party/recipe_engine/third_party/dateutil/tz.py
new file mode 100644
index 0000000000000000000000000000000000000000..0e28d6b3320953a71aace88d4043c80e2b71a4b8
--- /dev/null
+++ b/third_party/recipe_engine/third_party/dateutil/tz.py
@@ -0,0 +1,951 @@
+"""
+Copyright (c) 2003-2007  Gustavo Niemeyer <gustavo@niemeyer.net>
+
+This module offers extensions to the standard python 2.3+
+datetime module.
+"""
+__author__ = "Gustavo Niemeyer <gustavo@niemeyer.net>"
+__license__ = "PSF License"
+
+import datetime
+import struct
+import time
+import sys
+import os
+
+relativedelta = None
+parser = None
+rrule = None
+
+__all__ = ["tzutc", "tzoffset", "tzlocal", "tzfile", "tzrange",
+           "tzstr", "tzical", "tzwin", "tzwinlocal", "gettz"]
+
+try:
+    from dateutil.tzwin import tzwin, tzwinlocal
+except (ImportError, OSError):
+    tzwin, tzwinlocal = None, None
+
+ZERO = datetime.timedelta(0)
+EPOCHORDINAL = datetime.datetime.utcfromtimestamp(0).toordinal()
+
+class tzutc(datetime.tzinfo):
+
+    def utcoffset(self, dt):
+        return ZERO
+     
+    def dst(self, dt):
+        return ZERO
+
+    def tzname(self, dt):
+        return "UTC"
+
+    def __eq__(self, other):
+        return (isinstance(other, tzutc) or
+                (isinstance(other, tzoffset) and other._offset == ZERO))
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+    def __repr__(self):
+        return "%s()" % self.__class__.__name__
+
+    __reduce__ = object.__reduce__
+
+class tzoffset(datetime.tzinfo):
+
+    def __init__(self, name, offset):
+        self._name = name
+        self._offset = datetime.timedelta(seconds=offset)
+
+    def utcoffset(self, dt):
+        return self._offset
+
+    def dst(self, dt):
+        return ZERO
+
+    def tzname(self, dt):
+        return self._name
+
+    def __eq__(self, other):
+        return (isinstance(other, tzoffset) and
+                self._offset == other._offset)
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+    def __repr__(self):
+        return "%s(%s, %s)" % (self.__class__.__name__,
+                               `self._name`,
+                               self._offset.days*86400+self._offset.seconds)
+
+    __reduce__ = object.__reduce__
+
+class tzlocal(datetime.tzinfo):
+
+    _std_offset = datetime.timedelta(seconds=-time.timezone)
+    if time.daylight:
+        _dst_offset = datetime.timedelta(seconds=-time.altzone)
+    else:
+        _dst_offset = _std_offset
+
+    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):
+        return time.tzname[self._isdst(dt)]
+
+    def _isdst(self, dt):
+        # We can't use mktime here. It is unstable when deciding if
+        # the hour near to a change is DST or not.
+        # 
+        # timestamp = time.mktime((dt.year, dt.month, dt.day, dt.hour,
+        #                         dt.minute, dt.second, dt.weekday(), 0, -1))
+        # return time.localtime(timestamp).tm_isdst
+        #
+        # The code above yields the following result:
+        #
+        #>>> import tz, datetime
+        #>>> t = tz.tzlocal()
+        #>>> datetime.datetime(2003,2,15,23,tzinfo=t).tzname()
+        #'BRDT'
+        #>>> datetime.datetime(2003,2,16,0,tzinfo=t).tzname()
+        #'BRST'
+        #>>> datetime.datetime(2003,2,15,23,tzinfo=t).tzname()
+        #'BRST'
+        #>>> datetime.datetime(2003,2,15,22,tzinfo=t).tzname()
+        #'BRDT'
+        #>>> datetime.datetime(2003,2,15,23,tzinfo=t).tzname()
+        #'BRDT'
+        #
+        # Here is a more stable implementation:
+        #
+        timestamp = ((dt.toordinal() - EPOCHORDINAL) * 86400
+                     + dt.hour * 3600
+                     + dt.minute * 60
+                     + dt.second)
+        return time.localtime(timestamp+time.timezone).tm_isdst
+
+    def __eq__(self, other):
+        if not isinstance(other, tzlocal):
+            return False
+        return (self._std_offset == other._std_offset and
+                self._dst_offset == other._dst_offset)
+        return True
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+    def __repr__(self):
+        return "%s()" % self.__class__.__name__
+
+    __reduce__ = object.__reduce__
+
+class _ttinfo(object):
+    __slots__ = ["offset", "delta", "isdst", "abbr", "isstd", "isgmt"]
+
+    def __init__(self):
+        for attr in self.__slots__:
+            setattr(self, attr, None)
+
+    def __repr__(self):
+        l = []
+        for attr in self.__slots__:
+            value = getattr(self, attr)
+            if value is not None:
+                l.append("%s=%s" % (attr, `value`))
+        return "%s(%s)" % (self.__class__.__name__, ", ".join(l))
+
+    def __eq__(self, other):
+        if not isinstance(other, _ttinfo):
+            return False
+        return (self.offset == other.offset and
+                self.delta == other.delta and
+                self.isdst == other.isdst and
+                self.abbr == other.abbr and
+                self.isstd == other.isstd and
+                self.isgmt == other.isgmt)
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+    def __getstate__(self):
+        state = {}
+        for name in self.__slots__:
+            state[name] = getattr(self, name, None)
+        return state
+
+    def __setstate__(self, state):
+        for name in self.__slots__:
+            if name in state:
+                setattr(self, name, state[name])
+
+class tzfile(datetime.tzinfo):
+
+    # http://www.twinsun.com/tz/tz-link.htm
+    # ftp://elsie.nci.nih.gov/pub/tz*.tar.gz
+    
+    def __init__(self, fileobj):
+        if isinstance(fileobj, basestring):
+            self._filename = fileobj
+            fileobj = open(fileobj)
+        elif hasattr(fileobj, "name"):
+            self._filename = fileobj.name
+        else:
+            self._filename = `fileobj`
+
+        # From tzfile(5):
+        #
+        # The time zone information files used by tzset(3)
+        # begin with the magic characters "TZif" to identify
+        # them as time zone information files, followed by
+        # sixteen bytes reserved for future use, followed by
+        # six four-byte values of type long, written in a
+        # ``standard'' byte order (the high-order  byte
+        # of the value is written first).
+
+        if fileobj.read(4) != "TZif":
+            raise ValueError, "magic not found"
+
+        fileobj.read(16)
+
+        (
+         # The number of UTC/local indicators stored in the file.
+         ttisgmtcnt,
+
+         # The number of standard/wall indicators stored in the file.
+         ttisstdcnt,
+         
+         # The number of leap seconds for which data is
+         # stored in the file.
+         leapcnt,
+
+         # The number of "transition times" for which data
+         # is stored in the file.
+         timecnt,
+
+         # The number of "local time types" for which data
+         # is stored in the file (must not be zero).
+         typecnt,
+
+         # The  number  of  characters  of "time zone
+         # abbreviation strings" stored in the file.
+         charcnt,
+
+        ) = struct.unpack(">6l", fileobj.read(24))
+
+        # The above header is followed by tzh_timecnt four-byte
+        # values  of  type long,  sorted  in ascending order.
+        # These values are written in ``standard'' byte order.
+        # Each is used as a transition time (as  returned  by
+        # time(2)) at which the rules for computing local time
+        # change.
+
+        if timecnt:
+            self._trans_list = struct.unpack(">%dl" % timecnt,
+                                             fileobj.read(timecnt*4))
+        else:
+            self._trans_list = []
+
+        # Next come tzh_timecnt one-byte values of type unsigned
+        # char; each one tells which of the different types of
+        # ``local time'' types described in the file is associated
+        # with the same-indexed transition time. These values
+        # serve as indices into an array of ttinfo structures that
+        # appears next in the file.
+        
+        if timecnt:
+            self._trans_idx = struct.unpack(">%dB" % timecnt,
+                                            fileobj.read(timecnt))
+        else:
+            self._trans_idx = []
+        
+        # Each ttinfo structure is written as a four-byte value
+        # for tt_gmtoff  of  type long,  in  a  standard  byte
+        # order, followed  by a one-byte value for tt_isdst
+        # and a one-byte  value  for  tt_abbrind.   In  each
+        # structure, tt_gmtoff  gives  the  number  of
+        # seconds to be added to UTC, tt_isdst tells whether
+        # tm_isdst should be set by  localtime(3),  and
+        # tt_abbrind serves  as an index into the array of
+        # time zone abbreviation characters that follow the
+        # ttinfo structure(s) in the file.
+
+        ttinfo = []
+
+        for i in range(typecnt):
+            ttinfo.append(struct.unpack(">lbb", fileobj.read(6)))
+
+        abbr = fileobj.read(charcnt)
+
+        # Then there are tzh_leapcnt pairs of four-byte
+        # values, written in  standard byte  order;  the
+        # first  value  of  each pair gives the time (as
+        # returned by time(2)) at which a leap second
+        # occurs;  the  second  gives the  total  number of
+        # leap seconds to be applied after the given time.
+        # The pairs of values are sorted in ascending order
+        # by time.
+
+        # Not used, for now
+        if leapcnt:
+            leap = struct.unpack(">%dl" % (leapcnt*2),
+                                 fileobj.read(leapcnt*8))
+
+        # Then there are tzh_ttisstdcnt standard/wall
+        # indicators, each stored as a one-byte value;
+        # they tell whether the transition times associated
+        # with local time types were specified as standard
+        # time or wall clock time, and are used when
+        # a time zone file is used in handling POSIX-style
+        # time zone environment variables.
+
+        if ttisstdcnt:
+            isstd = struct.unpack(">%db" % ttisstdcnt,
+                                  fileobj.read(ttisstdcnt))
+
+        # 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 tti.delta-self._find_ttinfo(dt, laststd=1).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 dstabbr and start is None:
+            self._start_delta = relativedelta.relativedelta(
+                    hours=+2, month=4, day=1, weekday=relativedelta.SU(+1))
+        else:
+            self._start_delta = start
+        if dstabbr and 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.datetime(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"
+
+        # Here we break the compatibility with the TZ variable handling.
+        # GMT-3 actually *means* the timezone -3.
+        if res.stdabbr in ("GMT", "UTC"):
+            res.stdoffset *= -1
+
+        # 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)
+
+        if not res.dstabbr:
+            self._start_delta = None
+            self._end_delta = None
+        else:
+            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
+
+class _tzicalvtz(datetime.tzinfo):
+    def __init__(self, tzid, comps=[]):
+        self._tzid = tzid
+        self._comps = comps
+        self._cachedate = []
+        self._cachecomp = []
+
+    def _find_comp(self, dt):
+        if len(self._comps) == 1:
+            return self._comps[0]
+        dt = dt.replace(tzinfo=None)
+        try:
+            return self._cachecomp[self._cachedate.index(dt)]
+        except ValueError:
+            pass
+        lastcomp = None
+        lastcompdt = None
+        for comp in self._comps:
+            if not comp.isdst:
+                # Handle the extra hour in DST -> STD
+                compdt = comp.rrule.before(dt-comp.tzoffsetdiff, inc=True)
+            else:
+                compdt = comp.rrule.before(dt, inc=True)
+            if compdt and (not lastcompdt or lastcompdt < compdt):
+                lastcompdt = compdt
+                lastcomp = comp
+        if not lastcomp:
+            # RFC says nothing about what to do when a given
+            # time is before the first onset date. We'll look for the
+            # first standard component, or the first component, if
+            # none is found.
+            for comp in self._comps:
+                if not comp.isdst:
+                    lastcomp = comp
+                    break
+            else:
+                lastcomp = comp[0]
+        self._cachedate.insert(0, dt)
+        self._cachecomp.insert(0, lastcomp)
+        if len(self._cachedate) > 10:
+            self._cachedate.pop()
+            self._cachecomp.pop()
+        return lastcomp
+
+    def utcoffset(self, dt):
+        return self._find_comp(dt).tzoffsetto
+
+    def dst(self, dt):
+        comp = self._find_comp(dt)
+        if comp.isdst:
+            return comp.tzoffsetdiff
+        else:
+            return ZERO
+
+    def tzname(self, dt):
+        return self._find_comp(dt).tzname
+
+    def __repr__(self):
+        return "<tzicalvtz %s>" % `self._tzid`
+
+    __reduce__ = object.__reduce__
+
+class tzical:
+    def __init__(self, fileobj):
+        global rrule
+        if not rrule:
+            from dateutil import rrule
+
+        if isinstance(fileobj, basestring):
+            self._s = fileobj
+            fileobj = open(fileobj)
+        elif hasattr(fileobj, "name"):
+            self._s = fileobj.name
+        else:
+            self._s = `fileobj`
+
+        self._vtz = {}
+
+        self._parse_rfc(fileobj.read())
+
+    def keys(self):
+        return self._vtz.keys()
+
+    def get(self, tzid=None):
+        if tzid is None:
+            keys = self._vtz.keys()
+            if len(keys) == 0:
+                raise ValueError, "no timezones defined"
+            elif len(keys) > 1:
+                raise ValueError, "more than one timezone available"
+            tzid = keys[0]
+        return self._vtz.get(tzid)
+
+    def _parse_offset(self, s):
+        s = s.strip()
+        if not s:
+            raise ValueError, "empty offset"
+        if s[0] in ('+', '-'):
+            signal = (-1,+1)[s[0]=='+']
+            s = s[1:]
+        else:
+            signal = +1
+        if len(s) == 4:
+            return (int(s[:2])*3600+int(s[2:])*60)*signal
+        elif len(s) == 6:
+            return (int(s[:2])*3600+int(s[2:4])*60+int(s[4:]))*signal
+        else:
+            raise ValueError, "invalid offset: "+s
+
+    def _parse_rfc(self, s):
+        lines = s.splitlines()
+        if not lines:
+            raise ValueError, "empty string"
+
+        # Unfold
+        i = 0
+        while i < len(lines):
+            line = lines[i].rstrip()
+            if not line:
+                del lines[i]
+            elif i > 0 and line[0] == " ":
+                lines[i-1] += line[1:]
+                del lines[i]
+            else:
+                i += 1
+
+        tzid = None
+        comps = []
+        invtz = False
+        comptype = None
+        for line in lines:
+            if not line:
+                continue
+            name, value = line.split(':', 1)
+            parms = name.split(';')
+            if not parms:
+                raise ValueError, "empty property name"
+            name = parms[0].upper()
+            parms = parms[1:]
+            if invtz:
+                if name == "BEGIN":
+                    if value in ("STANDARD", "DAYLIGHT"):
+                        # Process component
+                        pass
+                    else:
+                        raise ValueError, "unknown component: "+value
+                    comptype = value
+                    founddtstart = False
+                    tzoffsetfrom = None
+                    tzoffsetto = None
+                    rrulelines = []
+                    tzname = None
+                elif name == "END":
+                    if value == "VTIMEZONE":
+                        if comptype:
+                            raise ValueError, \
+                                  "component not closed: "+comptype
+                        if not tzid:
+                            raise ValueError, \
+                                  "mandatory TZID not found"
+                        if not comps:
+                            raise ValueError, \
+                                  "at least one component is needed"
+                        # Process vtimezone
+                        self._vtz[tzid] = _tzicalvtz(tzid, comps)
+                        invtz = False
+                    elif value == comptype:
+                        if not founddtstart:
+                            raise ValueError, \
+                                  "mandatory DTSTART not found"
+                        if tzoffsetfrom is None:
+                            raise ValueError, \
+                                  "mandatory TZOFFSETFROM not found"
+                        if tzoffsetto is None:
+                            raise ValueError, \
+                                  "mandatory TZOFFSETFROM not found"
+                        # Process component
+                        rr = None
+                        if rrulelines:
+                            rr = rrule.rrulestr("\n".join(rrulelines),
+                                                compatible=True,
+                                                ignoretz=True,
+                                                cache=True)
+                        comp = _tzicalvtzcomp(tzoffsetfrom, tzoffsetto,
+                                              (comptype == "DAYLIGHT"),
+                                              tzname, rr)
+                        comps.append(comp)
+                        comptype = None
+                    else:
+                        raise ValueError, \
+                              "invalid component end: "+value
+                elif comptype:
+                    if name == "DTSTART":
+                        rrulelines.append(line)
+                        founddtstart = True
+                    elif name in ("RRULE", "RDATE", "EXRULE", "EXDATE"):
+                        rrulelines.append(line)
+                    elif name == "TZOFFSETFROM":
+                        if parms:
+                            raise ValueError, \
+                                  "unsupported %s parm: %s "%(name, parms[0])
+                        tzoffsetfrom = self._parse_offset(value)
+                    elif name == "TZOFFSETTO":
+                        if parms:
+                            raise ValueError, \
+                                  "unsupported TZOFFSETTO parm: "+parms[0]
+                        tzoffsetto = self._parse_offset(value)
+                    elif name == "TZNAME":
+                        if parms:
+                            raise ValueError, \
+                                  "unsupported TZNAME parm: "+parms[0]
+                        tzname = value
+                    elif name == "COMMENT":
+                        pass
+                    else:
+                        raise ValueError, "unsupported property: "+name
+                else:
+                    if name == "TZID":
+                        if parms:
+                            raise ValueError, \
+                                  "unsupported TZID parm: "+parms[0]
+                        tzid = value
+                    elif name in ("TZURL", "LAST-MODIFIED", "COMMENT"):
+                        pass
+                    else:
+                        raise ValueError, "unsupported property: "+name
+            elif name == "BEGIN" and value == "VTIMEZONE":
+                tzid = None
+                comps = []
+                invtz = True
+
+    def __repr__(self):
+        return "%s(%s)" % (self.__class__.__name__, `self._s`)
+
+if sys.platform != "win32":
+    TZFILES = ["/etc/localtime", "localtime"]
+    TZPATHS = ["/usr/share/zoneinfo", "/usr/lib/zoneinfo", "/etc/zoneinfo"]
+else:
+    TZFILES = []
+    TZPATHS = []
+
+def gettz(name=None):
+    tz = None
+    if not name:
+        try:
+            name = os.environ["TZ"]
+        except KeyError:
+            pass
+    if name is None or name == ":":
+        for filepath in TZFILES:
+            if not os.path.isabs(filepath):
+                filename = filepath
+                for path in TZPATHS:
+                    filepath = os.path.join(path, filename)
+                    if os.path.isfile(filepath):
+                        break
+                else:
+                    continue
+            if os.path.isfile(filepath):
+                try:
+                    tz = tzfile(filepath)
+                    break
+                except (IOError, OSError, ValueError):
+                    pass
+        else:
+            tz = tzlocal()
+    else:
+        if name.startswith(":"):
+            name = name[:-1]
+        if os.path.isabs(name):
+            if os.path.isfile(name):
+                tz = tzfile(name)
+            else:
+                tz = None
+        else:
+            for path in TZPATHS:
+                filepath = os.path.join(path, name)
+                if not os.path.isfile(filepath):
+                    filepath = filepath.replace(' ','_')
+                    if not os.path.isfile(filepath):
+                        continue
+                try:
+                    tz = tzfile(filepath)
+                    break
+                except (IOError, OSError, ValueError):
+                    pass
+            else:
+                tz = None
+                if tzwin:
+                    try:
+                        tz = tzwin(name)
+                    except OSError:
+                        pass
+                if not tz:
+                    from dateutil.zoneinfo import gettz
+                    tz = gettz(name)
+                if not tz:
+                    for c in name:
+                        # name must have at least one offset to be a tzstr
+                        if c in "0123456789":
+                            try:
+                                tz = tzstr(name)
+                            except ValueError:
+                                pass
+                            break
+                    else:
+                        if name in ("GMT", "UTC"):
+                            tz = tzutc()
+                        elif name in time.tzname:
+                            tz = tzlocal()
+    return tz
+
+# vim:ts=4:sw=4:et