PYTHON-1603 Truncate large datetimes properly

bson/__init__.py

@@ -819,7 +819,7 @@ def _dict_to_bson(doc, check_keys, opts, top_level=True):
 def _millis_to_datetime(millis, opts):
  """Convert milliseconds since epoch UTC to datetime."""
  diff = ((millis % 1000) + 1000) % 1000
- seconds = (millis - diff) / 1000
+ seconds = (millis - diff) // 1000
  micros = diff * 1000
  if opts.tz_aware:
  dt = EPOCH_AWARE + datetime.timedelta(seconds=seconds,
@@ -837,7 +837,7 @@ def _datetime_to_millis(dtm):
  if dtm.utcoffset() is not None:
  dtm = dtm - dtm.utcoffset()
  return int(calendar.timegm(dtm.timetuple()) * 1000 +
- dtm.microsecond / 1000)
+ dtm.microsecond // 1000)
 
 
 _CODEC_OPTIONS_TYPE_ERROR = TypeError(

test/test_bson.py

@@ -474,6 +474,13 @@ def test_datetime_encode_decode(self):
  dt2 = BSON.encode({"date": dt1}).decode()["date"]
  self.assertEqual(dt1, dt2)
 
+ def test_large_datetime_truncation(self):
+ # Ensure that a large datetime is truncated correctly.
+ dt1 = datetime.datetime(9999, 1, 1, 1, 1, 1, 999999)
+ dt2 = BSON.encode({"date": dt1}).decode()["date"]
+ self.assertEqual(dt2.microsecond, 999000)
+ self.assertEqual(dt2.second, dt1.second)
+
  def test_aware_datetime(self):
  aware = datetime.datetime(1993, 4, 4, 2,
  tzinfo=FixedOffset(555, "SomeZone"))