omni-pca/tests/test_programs.py
Ryan Malloy e560d98f87 programs: add multi-record decoder properties (firmware >=3.0 records)
The 6 multi-record ProgType values (WHEN/AT/EVERY/AND/OR/THEN) now have
typed accessors on the Program dataclass:

  is_multi_record()  - classifier for ProgTypes 5-10
  event_id           - WHEN trigger event-id (same property as EVENT, no
                       Mon/Day swap, BE wire form)
  and_family         - AND record byte-1 family + operand bits (mirrors
                       compact-form cond's high byte: ZONE=0x04, CTRL+ON=0x0A,
                       OTHER=0x00, etc.)
  and_instance       - AND record bytes 3-4 BE u16 (zone#, unit#,
                       MiscConditional value, ...)
  every_interval     - EVERY record bytes 3-4 BE u16 (recurrence interval)

AT records reuse the existing month/day/days/hour/minute fields (same
byte layout as compact-form TIMED, just with cmd/par/pr2 zero).
OR records carry no payload — only the ProgType byte distinguishes
them. THEN records reuse cmd/par/pr2 (same layout and LE byte order
as compact-form action fields).

10 new tests cover the empirical captures from pca-re/clausal-re:

  - is_multi_record() classifier
  - WHEN event_id for Zone 5 Secure and Zone 1 Secure
  - EVERY 5 SECONDS interval decoding
  - AND IF UNIT 1 ON, AND IF ZONE 5 SECURE, AND IF NEVER family+instance
  - AT record month/day/days/hour/minute
  - OR record all-zero invariants
  - THEN record cmd/par/pr2 (UNIT 1 ON)

All byte vectors in the tests come from real PC Access captures in
pca-re/clausal-re/06-10.pca with firmware override at 3.0+.

The and_family and and_instance properties derive from the existing
cond and cond2 fields via byte-swap — disk bytes 1-4 of AND records
use BE u16 order, but Program's cond/cond2 fields are LE-decoded
(per compact-form convention). The byte-swap formula
((cond2 & 0xFF) << 8) | ((cond2 >> 8) & 0xFF) yields the BE
interpretation without re-reading raw bytes.

473 tests passing (up from 463).
2026-05-12 04:57:48 -06:00

571 lines
21 KiB
Python

"""Unit tests for omni_pca.programs.
Three layers of evidence (no external oracle, so we triangulate):
* **Golden bytes per ProgramType** — hand-curated byte vectors that
exercise the layout-specific paths (Mon/Day swap for Event, Remark
variant with RemarkID at bytes 1-4).
* **Round-trip property** — random 14-byte inputs survive
``decode(b).encode() == b`` for both wire and file layouts.
* **Unknown-enum tolerance** — bytes outside ``ProgramType`` /
``Command`` enum domains pass through without raising.
"""
from __future__ import annotations
import os
import struct
import warnings
import pytest
from omni_pca.programs import (
MAX_PROGRAMS,
PROGRAM_BYTES,
Days,
Program,
ProgramType,
decode_program_table,
iter_defined,
)
# ---- golden bytes ---------------------------------------------------------
def test_timed_decodes_canonical_example() -> None:
"""The worked example from the docs page — TIMED program.
``cond``, ``cond2`` and ``pr2`` are **little-endian** u16 fields:
byte N is the low byte, byte N+1 the high byte. The byte vector
below comes from ``Our_House.pca`` slot 22 (a real TIMED program
for an HLC scene at 07:15 weekday mornings).
"""
body = bytes.fromhex("018d099b094403010008 0c3e070f".replace(" ", ""))
p = Program.from_file_record(body, slot=22)
assert p.slot == 22
assert p.prog_type == ProgramType.TIMED
# bytes 1,2 = [8d 09] → LE u16 = 0x098D
assert p.cond == 0x098D
# bytes 3,4 = [9b 09] → LE u16 = 0x099B
assert p.cond2 == 0x099B
assert p.cmd == 0x44
assert p.par == 3
# bytes 7,8 = [01 00] → LE u16 = 0x0001 (object #1)
assert p.pr2 == 0x0001
assert p.month == 8
assert p.day == 12
assert p.days == 0x3E
assert p.hour == 7
assert p.minute == 15
assert p.remark_id is None
# round-trip on file form
assert p.encode_file_record() == body
def test_event_swaps_mon_day_on_file_layout() -> None:
"""EVENT programs store [day, month] at offsets 9/10 on disk.
File bytes 9-10 = ``05 0c`` should decode to day=5, month=12 (not
month=5, day=12). Encoding back must preserve the swap so the
raw .pca slot bytes don't drift.
"""
body = bytes.fromhex("020c04000001010000050cff070f") # 14 bytes
assert len(body) == 14
p = Program.from_file_record(body, slot=1)
assert p.prog_type == ProgramType.EVENT
# Disk had [05, 0c] but EVENT swap means [day, mon].
assert p.day == 5
assert p.month == 12
# Round-trip MUST re-apply the swap.
assert p.encode_file_record() == body
def test_event_no_swap_on_wire_layout() -> None:
"""Same EVENT-type bytes via the wire decoder: NO swap.
On the wire ``clsOLMsgProgramData`` always stores [month, day] at
offsets 9/10 regardless of prog_type — only the .pca file form
swaps. This test catches a regression where we accidentally swap
in the wire path.
"""
body = bytes.fromhex("020c04000001010000050cff070f")
p = Program.from_wire_bytes(body, slot=1)
assert p.prog_type == ProgramType.EVENT
# Wire form: byte 9 = month, byte 10 = day. NO swap.
assert p.month == 5
assert p.day == 12
assert p.encode_wire_bytes() == body
def test_yearly_program() -> None:
"""YEARLY programs use month + day fields semantically — no swap."""
body = bytes.fromhex("03000000000100008b010a0f00000001")[:14]
p = Program.from_file_record(body, slot=10)
assert p.prog_type == ProgramType.YEARLY
assert p.month == 0x01
assert p.day == 0x0A
assert p.encode_file_record() == body
def test_remark_uses_bytes_1_to_4_as_remark_id() -> None:
"""REMARK programs (prog_type=4) pack a 32-bit BE RemarkID into
bytes 1-4 in place of cond + cond2."""
remark_id = 0xDEADBEEF
body = (
bytes([int(ProgramType.REMARK)])
+ struct.pack(">I", remark_id)
+ bytes(9)
)
assert len(body) == 14
p = Program.from_file_record(body)
assert p.prog_type == ProgramType.REMARK
assert p.remark_id == remark_id
# cond / cond2 are zeroed in the dataclass — the bytes there are
# the RemarkID, not condition fields.
assert p.cond == 0
assert p.cond2 == 0
# Round-trip restores the RemarkID bytes verbatim.
assert p.encode_file_record() == body
def test_all_zero_slot_is_empty() -> None:
"""A free slot decodes cleanly and round-trips."""
p = Program.from_file_record(b"\x00" * 14, slot=999)
assert p.is_empty()
assert p.prog_type == ProgramType.FREE
assert p.encode_file_record() == b"\x00" * 14
assert p.encode_wire_bytes() == b"\x00" * 14
# ---- round-trip property ---------------------------------------------------
def test_random_round_trip_wire() -> None:
"""500 random 14-byte inputs: ``decode_wire → encode_wire == input``.
The wire path is the simpler one (no Mon/Day swap), so it should
round-trip every byte pattern losslessly.
"""
with warnings.catch_warnings():
warnings.simplefilter("ignore", UserWarning)
for _ in range(500):
body = os.urandom(14)
# Skip Remark inputs in this round — the dataclass discards
# cond/cond2 for Remark types and re-derives them from
# remark_id, but with no separate cond field we'd lose
# bytes that happen to differ; the next test covers Remark
# explicitly.
if body[0] == int(ProgramType.REMARK):
continue
p = Program.from_wire_bytes(body)
assert p.encode_wire_bytes() == body
def test_random_round_trip_file() -> None:
"""500 random 14-byte inputs through the file (Mon/Day swap) form."""
with warnings.catch_warnings():
warnings.simplefilter("ignore", UserWarning)
for _ in range(500):
body = os.urandom(14)
if body[0] == int(ProgramType.REMARK):
continue
p = Program.from_file_record(body)
assert p.encode_file_record() == body
def test_remark_round_trip() -> None:
"""Remark variant round-trip — explicitly, with random RemarkIDs."""
for _ in range(200):
remark_id_bytes = os.urandom(4)
body = (
bytes([int(ProgramType.REMARK)])
+ remark_id_bytes
+ os.urandom(9)
)
p_file = Program.from_file_record(body)
assert p_file.encode_file_record() == body
p_wire = Program.from_wire_bytes(body)
assert p_wire.encode_wire_bytes() == body
# ---- unknown-enum tolerance ------------------------------------------------
def test_unknown_prog_type_passes_through_with_warning() -> None:
"""Bytes outside ProgramType (0..10) decode to a raw int + warning.
Reset the once-per-process cache first; otherwise earlier random
round-trip tests may have already seen this value and silenced
the warning.
"""
import omni_pca.programs as pm
pm._warned_unknown.clear()
body = bytes([0x42]) + bytes(13)
with warnings.catch_warnings(record=True) as caught:
warnings.simplefilter("always")
p = Program.from_wire_bytes(body)
assert p.prog_type == 0x42
assert p.encode_wire_bytes() == body
assert any("ProgramType" in str(w.message) for w in caught)
def test_unknown_cmd_passes_through() -> None:
"""Unrecognised cmd bytes decode without raising."""
body = bytes([int(ProgramType.TIMED), 0, 0, 0, 0, 0xFA, 0]) + bytes(7)
p = Program.from_wire_bytes(body)
assert p.cmd == 0xFA
assert p.encode_wire_bytes() == body
# ---- table decode ----------------------------------------------------------
def test_decode_program_table_size_validation() -> None:
with pytest.raises(ValueError, match="must be 21000 bytes"):
decode_program_table(b"\x00" * 100)
def test_decode_program_table_round_trip_all_zero() -> None:
"""All-zero 21000-byte blob round-trips, slot numbers are 1..1500."""
blob = b"\x00" * (MAX_PROGRAMS * PROGRAM_BYTES)
programs = decode_program_table(blob)
assert len(programs) == MAX_PROGRAMS
assert programs[0].slot == 1
assert programs[-1].slot == MAX_PROGRAMS
assert all(p.is_empty() for p in programs)
assert list(iter_defined(programs)) == []
rebuilt = b"".join(p.encode_file_record() for p in programs)
assert rebuilt == blob
def test_iter_defined_filters_empty() -> None:
p1 = Program(prog_type=int(ProgramType.TIMED), slot=1, cmd=1, hour=8)
p2 = Program(slot=2) # empty
p3 = Program(prog_type=int(ProgramType.EVENT), slot=3, cmd=2)
defined = list(iter_defined((p1, p2, p3)))
assert defined == [p1, p3]
# ---- Days bitmask sanity --------------------------------------------------
def test_days_bitmask_values() -> None:
"""Sanity-check the enuDays values against the C# definition."""
assert Days.MONDAY == 0x02
assert Days.SUNDAY == 0x80
assert Days.MONDAY | Days.WEDNESDAY | Days.FRIDAY == 0x2A
# ---- TimeKind classification + sunrise/sunset offsets ----------------------
from omni_pca.programs import TimeKind # noqa: E402
@pytest.mark.parametrize(
"hour, minute, expected_kind, expected_offset, expected_label",
[
# Absolute times — hour 0..23, minute 0..59.
(0, 0, TimeKind.ABSOLUTE, 0, "00:00"),
(7, 15, TimeKind.ABSOLUTE, 0, "07:15"),
(23, 59, TimeKind.ABSOLUTE, 0, "23:59"),
# Sunrise-relative.
(25, 0, TimeKind.SUNRISE, 0, "at sunrise"),
(25, 30, TimeKind.SUNRISE, 30, "30 min after sunrise"),
(25, 226, TimeKind.SUNRISE, -30, "30 min before sunrise"),
(25, 255, TimeKind.SUNRISE, -1, "1 min before sunrise"),
(25, 127, TimeKind.SUNRISE, 127, "127 min after sunrise"),
# Sunset-relative.
(26, 0, TimeKind.SUNSET, 0, "at sunset"),
(26, 10, TimeKind.SUNSET, 10, "10 min after sunset"),
(26, 246, TimeKind.SUNSET, -10, "10 min before sunset"),
(26, 128, TimeKind.SUNSET, -128, "128 min before sunset"),
],
)
def test_time_kind_classification(
hour, minute, expected_kind, expected_offset, expected_label
) -> None:
p = Program(
prog_type=int(ProgramType.TIMED),
hour=hour, minute=minute, days=int(Days.MONDAY),
)
assert p.time_kind == expected_kind
assert p.time_offset_minutes == expected_offset
assert p.format_time() == expected_label
def test_time_kind_round_trip_through_wire() -> None:
"""Build a sunset-relative program, encode → decode → assert preserved."""
p = Program(
prog_type=int(ProgramType.TIMED),
hour=26, minute=246, # 10 min before sunset
days=int(Days.FRIDAY | Days.SATURDAY),
)
body = p.encode_wire_bytes()
p2 = Program.from_wire_bytes(body)
assert p2.time_kind == TimeKind.SUNSET
assert p2.time_offset_minutes == -10
assert p2.format_time() == "10 min before sunset"
# ---- Condition bit-split decoder -----------------------------------------
from omni_pca.programs import ( # noqa: E402
Condition,
ConditionFamily,
MiscConditional,
)
def test_condition_empty() -> None:
"""cond == 0 → no condition applies."""
c = Condition.decode(0)
assert c.is_empty()
assert c.family is ConditionFamily.OTHER
assert c.describe() == "(no condition)"
@pytest.mark.parametrize(
"cond, family, selector, operand, expected_describe",
[
# OTHER family — bits 0-3 = MiscConditional value
(0x0000, ConditionFamily.OTHER, 0, 0, "(no condition)"),
(0x0002, ConditionFamily.OTHER, 2, 0, "LIGHT"),
(0x0003, ConditionFamily.OTHER, 3, 0, "DARK"),
(0x0008, ConditionFamily.OTHER, 8, 0, "AC_POWER_OFF"),
(0x000B, ConditionFamily.OTHER, 11, 0, "BATTERY_OK"),
(0x010B, ConditionFamily.OTHER, 11, 0, "BATTERY_OK"), # high bits ignored
# ZONE family — bits 0-7 = zone, bit 9 = NOT_READY (1) / SECURE (0)
(0x0405, ConditionFamily.ZONE, 5, 0, "Zone 5 SECURE"),
(0x0605, ConditionFamily.ZONE, 5, 1, "Zone 5 NOT_READY"),
(0x040B, ConditionFamily.ZONE, 11, 0, "Zone 11 SECURE"),
# CTRL family — bits 0-8 = unit, bit 9 = ON (1) / OFF (0)
(0x0801, ConditionFamily.CTRL, 1, 0, "Unit 1 OFF"),
(0x0A01, ConditionFamily.CTRL, 1, 1, "Unit 1 ON"),
(0x09FF, ConditionFamily.CTRL, 0x1FF, 0, "Unit 511 OFF"), # 9-bit unit
# TIME family — bits 0-7 = clock, bit 9 = ENABLED (1) / DISABLED (0)
(0x0C04, ConditionFamily.TIME, 4, 0, "Time clock 4 DISABLED"),
(0x0E03, ConditionFamily.TIME, 3, 1, "Time clock 3 ENABLED"),
# SEC family — bits 8-11 = area, bits 12-14 = mode, bit 15 = arming flag
# mode=Off (0) with bit 15: encode of "area X is in mode Off"
(0x8100, ConditionFamily.SEC, 1, 0, "Area 1 OFF"),
(0x8800, ConditionFamily.SEC, 8, 0, "Area 8 OFF"),
# mode=Day (1), no exit-delay flag → not arming-transition
(0x1100, ConditionFamily.SEC, 1, 1, "Area 1 DAY"),
# mode=Away (3), bit 15 set → ARMING (in transition)
(0xB100, ConditionFamily.SEC, 1, 3, "Area 1 ARMING AWAY"),
# area=0 selector → "(any area)"
(0x9000, ConditionFamily.SEC, 0, 1, "(any area) ARMING DAY"),
],
)
def test_condition_decode_per_family(
cond, family, selector, operand, expected_describe
) -> None:
c = Condition.decode(cond)
assert c.family == family, (
f"cond={cond:#06x} family expected {family.name}, got {c.family.name}"
)
assert c.selector == selector, f"cond={cond:#06x} selector"
assert c.operand == operand, f"cond={cond:#06x} operand"
assert c.describe() == expected_describe
def test_condition_arming_transition_flag_only_when_mode_nonzero() -> None:
"""Bit 15 + mode=Off is the 'plain off' encoding, NOT an arming transition.
Per clsText.cs:2263, the arming-transition branch requires
``(cond & 0xF000) != 0x8000``, which fails when only bit 15 is set
(mode bits 12-14 are zero).
"""
plain_off = Condition.decode(0x8100)
assert plain_off.arming_transition is False
assert plain_off.describe() == "Area 1 OFF"
arming = Condition.decode(0xB100) # bit 15 + mode=3 (AWAY)
assert arming.arming_transition is True
assert "ARMING" in arming.describe()
def test_program_condition_helpers() -> None:
"""Program.condition() / condition2() decode the raw u16 fields."""
p = Program(
prog_type=int(ProgramType.TIMED),
cond=0x0605, # Zone 5 NOT_READY
cond2=0xB100, # Area 1 ARMING AWAY
)
c1 = p.condition()
c2 = p.condition2()
assert c1.family is ConditionFamily.ZONE
assert c1.selector == 5
assert c1.describe() == "Zone 5 NOT_READY"
assert c2.family is ConditionFamily.SEC
assert c2.describe() == "Area 1 ARMING AWAY"
def test_condition_rejects_out_of_u16_range() -> None:
with pytest.raises(ValueError):
Condition.decode(-1)
with pytest.raises(ValueError):
Condition.decode(0x10000)
def test_misc_conditional_enum_matches_csharp() -> None:
"""enuMiscConditional values mirrored from clsText.cs."""
assert MiscConditional.NONE == 0
assert MiscConditional.DARK == 3
assert MiscConditional.AC_POWER_OFF == 8
assert MiscConditional.BATTERY_OK == 11
assert MiscConditional.ENERGY_COST_CRITICAL == 15
# ---- multi-record (firmware ≥3.0.0) decoder properties ----------------
def test_is_multi_record_classifier() -> None:
"""Compact-form ProgTypes (0-4) are NOT multi-record; 5-10 ARE."""
for pt in (
ProgramType.FREE,
ProgramType.TIMED,
ProgramType.EVENT,
ProgramType.YEARLY,
ProgramType.REMARK,
):
p = Program(prog_type=int(pt))
assert not p.is_multi_record(), f"{pt.name} should NOT be multi-record"
for pt in (
ProgramType.WHEN,
ProgramType.AT,
ProgramType.EVERY,
ProgramType.AND,
ProgramType.OR,
ProgramType.THEN,
):
p = Program(prog_type=int(pt))
assert p.is_multi_record(), f"{pt.name} SHOULD be multi-record"
def test_when_event_id_zone_5_secure() -> None:
"""WHEN record bytes 9-10 = (family, instance) in BE wire form.
Empirical capture: "WHEN ZONE 5 SECURE" yields bytes 9-10 = [04, 05]
→ event_id = 0x0405 (= (ZONE=4, instance=5)).
"""
body = bytes.fromhex("05 00 00 00 00 00 00 00 00 04 05 00 00 00".replace(" ", ""))
p = Program.from_file_record(body, slot=17)
assert p.prog_type == ProgramType.WHEN
assert p.event_id == 0x0405
# The family code 0x04 in the high byte matches ProgramCond.ZONE
assert (p.event_id >> 8) & 0xFC == 0x04 # ZONE family
assert p.event_id & 0xFF == 0x05 # zone # 5
def test_when_event_id_zone_1_secure() -> None:
"""Second WHEN capture: ZONE 1 SECURE → event_id 0x0401."""
body = bytes.fromhex("05 00 00 00 00 00 00 00 00 04 01 00 00 00".replace(" ", ""))
p = Program.from_file_record(body, slot=6)
assert p.prog_type == ProgramType.WHEN
assert p.event_id == 0x0401
def test_every_interval_5_seconds() -> None:
"""EVERY record: interval at bytes 3-4 BE.
Empirical capture: "EVERY 5 SECONDS" trigger yields
08 00 00 00 05 00 ... at byte positions 0-5 (ProgType=7 at byte 0,
then zeros until byte 4 = 0x05 holding the interval low byte).
"""
body = bytes.fromhex("07 00 00 00 05 00 00 00 00 00 00 00 00 00".replace(" ", ""))
p = Program.from_file_record(body, slot=2)
assert p.prog_type == ProgramType.EVERY
assert p.every_interval == 5
def test_and_unit_1_on() -> None:
"""AND IF UNIT 1 ON: byte 1 = 0x0A (CTRL family + ON bit), bytes 3-4 BE = 1.
Empirical capture from block 9 slot 18 — the structured AND test.
"""
body = bytes.fromhex("08 0a 00 00 01 00 00 00 00 00 00 00 00 00".replace(" ", ""))
p = Program.from_file_record(body, slot=18)
assert p.prog_type == ProgramType.AND
# Byte 1 = 0x0a in the high byte means CTRL family (0x08) + ON bit (0x02)
assert p.and_family == 0x0A
# Family code (top 6 bits): CTRL = 0x08
assert p.and_family & 0xFC == 0x08
# Operand bit (bit 1 of family byte = bit 9 of compact cond u16): ON
assert p.and_family & 0x02 == 0x02
# Instance = unit #
assert p.and_instance == 1
def test_and_zone_5_secure() -> None:
"""AND IF ZONE 5 SECURE: byte 1 = 0x04 (ZONE + SECURE), bytes 3-4 BE = 5."""
body = bytes.fromhex("08 04 00 00 05 00 00 00 00 00 00 00 00 00".replace(" ", ""))
p = Program.from_file_record(body, slot=7)
assert p.prog_type == ProgramType.AND
assert p.and_family == 0x04 # ZONE family, SECURE operand (bit 1 = 0)
assert p.and_family & 0xFC == 0x04 # ZONE family
assert p.and_family & 0x02 == 0 # SECURE (operand bit clear)
assert p.and_instance == 5 # zone # 5
def test_and_never() -> None:
"""AND IF NEVER: byte 1 = 0x00 (OTHER family), bytes 3-4 BE = 1 (NEVER value)."""
body = bytes.fromhex("08 00 00 00 01 00 00 00 00 00 00 00 00 00".replace(" ", ""))
p = Program.from_file_record(body, slot=8)
assert p.prog_type == ProgramType.AND
assert p.and_family == 0x00 # OTHER family
assert p.and_instance == int(MiscConditional.NEVER) # = 1
def test_at_record_layout() -> None:
"""AT record (multi-record TIMED): same byte layout as compact TIMED.
Empirical capture: AT 12:01 AM all-7-days yields:
06 00 00 00 00 00 00 00 00 05 0c fe 00 01
Where bytes 9-10 = [05, 0c] (month=5, day=12; no Mon/Day swap
since AT isn't EVENT-typed), byte 11 = 0xfe (Days: all 7),
bytes 12-13 = 00:01.
"""
body = bytes.fromhex("06 00 00 00 00 00 00 00 00 05 0c fe 00 01".replace(" ", ""))
p = Program.from_file_record(body, slot=7)
assert p.prog_type == ProgramType.AT
assert p.month == 5
assert p.day == 12
assert p.days == 0xFE # MTWTFSS (bit 1 through bit 7)
assert p.hour == 0
assert p.minute == 1
def test_or_record_is_pure_discriminator() -> None:
"""OR record: only ProgType set, all other bytes zero."""
body = bytes.fromhex("09 00 00 00 00 00 00 00 00 00 00 00 00 00".replace(" ", ""))
p = Program.from_file_record(body, slot=10)
assert p.prog_type == ProgramType.OR
assert p.cond == 0
assert p.cond2 == 0
assert p.cmd == 0
assert p.par == 0
assert p.pr2 == 0
assert p.month == 0
assert p.day == 0
assert p.days == 0
assert p.hour == 0
assert p.minute == 0
def test_then_record_uses_compact_action_layout() -> None:
"""THEN record (multi-record action): same cmd/par/pr2 layout as compact form.
Empirical capture: THEN UNIT 1 ON yields
0a 00 00 00 00 01 00 01 00 00 00 00 00 00
with cmd=1 (On), par=0, pr2=1 (UNIT 1, LE).
"""
body = bytes.fromhex("0a 00 00 00 00 01 00 01 00 00 00 00 00 00".replace(" ", ""))
p = Program.from_file_record(body, slot=10)
assert p.prog_type == ProgramType.THEN
assert p.cmd == 1 # enuUnitCommand.On
assert p.par == 0
assert p.pr2 == 1 # UNIT 1 (LE u16 at bytes 7-8, same as compact)