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stbi/Lib/site-packages/pytz/tzfile.py

+#!/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)