tools: Check that STDOFF can fit in 8-bits and deltaOffset can fit in…

… 4-bits (#18)

tools/transformer.py

@@ -453,9 +453,10 @@ def _create_zones_with_expanded_offset_string(self, zones_map):
  if offset_seconds == INVALID_SECONDS:
  valid = False
  _add_reason(removed_zones, name,
- f"invalid STDOFF offset string '{offset_string}'")
+ f"invalid STDOFF '{offset_string}'")
  break
 
+ # Truncate to requested granularity.
  offset_seconds_truncated = truncate_to_granularity(
  offset_seconds, self.offset_granularity)
  if offset_seconds != offset_seconds_truncated:
@@ -470,6 +471,15 @@ def _create_zones_with_expanded_offset_string(self, zones_map):
  _add_reason(notable_zones, name,
  f"STDOFF '{offset_string}' truncated to '{hm}'")
 
+ # Check that offset seconds can fit in a timeCode field
+ # implemented as a signed byte in multiples of 15-minutes.
+ offset_code = div_to_zero(offset_seconds_truncated, 900)
+ if offset_code < -127 or offset_code > 127:
+ valid = False
+ _add_reason(removed_zones, name,
+ f"STDOFF '{offset_string}' too large for 8-bits")
+ break
+
  era.offsetSeconds = offset_seconds
  era.offsetSecondsTruncated = offset_seconds_truncated
 
@@ -1111,6 +1121,7 @@ def _create_rules_with_expanded_delta_offset(self, rules_map):
  f"invalid deltaOffset '{delta_offset}'")
  break
 
+ # Truncate to requested granularity.
  delta_seconds_truncated = truncate_to_granularity(
  delta_seconds, self.offset_granularity)
  if delta_seconds != delta_seconds_truncated:
@@ -1127,6 +1138,17 @@ def _create_rules_with_expanded_delta_offset(self, rules_map):
  f"a multiple of '{self.offset_granularity}' "
  f"seconds")
 
+ # Check that delta seconds can fit in a 4-bit timeCode field
+ # with 15-minute granularity, defined as (timeCode =
+ # delta_seconds / 900s + 1h) which encodes -1:00 as 0 and 3:45
+ # as 15.
+ delta_code = div_to_zero(delta_seconds_truncated, 900) + 4
+ if delta_code < 0 or delta_code > 15:
+ valid = False
+ _add_reason(removed_policies, name,
+ f"deltaOffset '{delta_offset}' too large for 4-bits")
+ break
+
  rule.deltaSeconds = delta_seconds
  rule.deltaSecondsTruncated = delta_seconds_truncated
  if valid:
@@ -1385,8 +1407,11 @@ def calc_day_of_month(year, month, on_day_of_week, on_day_of_month):
 
  if on_day_of_month == 0:
  # lastXxx == (Xxx >= (daysInMonth - 6))
- on_day_of_month = days_in_month(year, month) - 6
- limit_date = datetime.date(year, month, on_day_of_month)
+ dom = days_in_month(year, month) - 6
+ else:
+ dom = on_day_of_month
+
+ limit_date = datetime.date(year, month, dom)
  day_of_week_shift = (on_day_of_week - limit_date.isoweekday() + 7) % 7
  return on_day_of_month + day_of_week_shift