python: Add NT Time utility functions

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

diff --git a/python/samba/nt_time.py b/python/samba/nt_time.py
new file mode 100644 (file)
index 0000000..69e01d6
--- /dev/null
+++ b/python/samba/nt_time.py
@@ -0,0 +1,60 @@
+#
+# NT Time utility functions.
+#
+# Copyright (C) Catalyst.Net Ltd 2023
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#
+
+import datetime
+from typing import Final, NewType
+
+
+NtTime = NewType("NtTime", int)
+NtTimeDelta = NewType("NtTimeDelta", int)
+
+
+NT_EPOCH: Final = datetime.datetime(
+    1601, 1, 1, 0, 0, 0, 0, tzinfo=datetime.timezone.utc
+)
+NT_TICKS_PER_μSEC: Final = 10
+NT_TICKS_PER_SEC: Final = NT_TICKS_PER_μSEC * 10**6
+
+
+def _validate_nt_time(nt_time: NtTime) -> None:
+    if not isinstance(nt_time, int):
+        raise ValueError(f"{nt_time} is not an integer")
+    if not 0 <= nt_time < 2**64:
+        raise ValueError(f"{nt_time} is out of range")
+
+
+def nt_time_from_datetime(tm: datetime.datetime) -> NtTime:
+    time_since_epoch = tm - NT_EPOCH
+    nt_time = NtTime(round(time_since_epoch.total_seconds() * NT_TICKS_PER_SEC))
+    _validate_nt_time(nt_time)
+    return nt_time
+
+
+def datetime_from_nt_time(nt_time: NtTime) -> datetime.datetime:
+    _validate_nt_time(nt_time)
+    time_since_epoch = datetime.timedelta(microseconds=nt_time / NT_TICKS_PER_μSEC)
+    return NT_EPOCH + time_since_epoch
+
+
+def nt_time_delta_from_datetime(dt: datetime.timedelta) -> NtTimeDelta:
+    return NtTimeDelta(round(dt.total_seconds() * NT_TICKS_PER_SEC))
+
+
+def timedelta_from_nt_time_delta(nt_time_delta: NtTimeDelta) -> datetime.timedelta:
+    return datetime.timedelta(microseconds=nt_time_delta / NT_TICKS_PER_μSEC)