1 files changed, 81 insertions, 0 deletions
diff --git a/Tools/tz/zdump.py b/Tools/tz/zdump.py
new file mode 100644
index 0000000000..f94b483101
--- /dev/null
+++ b/Tools/tz/zdump.py
@@ -0,0 +1,81 @@
+import sys
+import os
+import struct
+from array import array
+from collections import namedtuple
+from datetime import datetime, timedelta
+
+ttinfo = namedtuple('ttinfo', ['tt_gmtoff', 'tt_isdst', 'tt_abbrind'])
+
+class TZInfo:
+    def __init__(self, transitions, type_indices, ttis, abbrs):
+        self.transitions = transitions
+        self.type_indices = type_indices
+        self.ttis = ttis
+        self.abbrs = abbrs
+
+    @classmethod
+    def fromfile(cls, fileobj):
+        if fileobj.read(4).decode() != "TZif":
+            raise ValueError("not a zoneinfo file")
+        fileobj.seek(20)
+        header = fileobj.read(24)
+        tzh = (tzh_ttisgmtcnt, tzh_ttisstdcnt, tzh_leapcnt,
+               tzh_timecnt, tzh_typecnt, tzh_charcnt) = struct.unpack(">6l", header)
+        transitions = array('i')
+        transitions.fromfile(fileobj, tzh_timecnt)
+        if sys.byteorder != 'big':
+            transitions.byteswap()
+
+        type_indices = array('B')
+        type_indices.fromfile(fileobj, tzh_timecnt)
+
+        ttis = []
+        for i in range(tzh_typecnt):
+            ttis.append(ttinfo._make(struct.unpack(">lbb", fileobj.read(6))))
+
+        abbrs = fileobj.read(tzh_charcnt)
+
+        self = cls(transitions, type_indices, ttis, abbrs)
+        self.tzh = tzh
+
+        return self
+
+    def dump(self, stream, start=None, end=None):
+        for j, (trans, i) in enumerate(zip(self.transitions, self.type_indices)):
+            utc = datetime.utcfromtimestamp(trans)
+            tti = self.ttis[i]
+            lmt = datetime.utcfromtimestamp(trans + tti.tt_gmtoff)
+            abbrind = tti.tt_abbrind
+            abbr = self.abbrs[abbrind:self.abbrs.find(0, abbrind)].decode()
+            if j > 0:
+                prev_tti = self.ttis[self.type_indices[j - 1]]
+                shift = " %+g" % ((tti.tt_gmtoff - prev_tti.tt_gmtoff) / 3600)
+            else:
+                shift = ''
+            print("%s UTC = %s %-5s isdst=%d" % (utc, lmt, abbr, tti[1]) + shift, file=stream)
+
+    @classmethod
+    def zonelist(cls, zonedir='/usr/share/zoneinfo'):
+        zones = []
+        for root, _, files in os.walk(zonedir):
+            for f in files:
+                p = os.path.join(root, f)
+                with open(p, 'rb') as o:
+                    magic =  o.read(4)
+                if magic == b'TZif':
+                    zones.append(p[len(zonedir) + 1:])
+        return zones
+
+if __name__ == '__main__':
+    if len(sys.argv) < 2:
+        zones = TZInfo.zonelist()
+        for z in zones:
+            print(z)
+        sys.exit()
+    filepath = sys.argv[1]
+    if not filepath.startswith('/'):
+        filepath = os.path.join('/usr/share/zoneinfo', filepath)
+    with open(filepath, 'rb') as fileobj:
+        tzi = TZInfo.fromfile(fileobj)
+    tzi.dump(sys.stdout)