def decode_to_spp_packets(
self,
datalink_list: List[TCDataLinkPacket]
):
"""
Given a list of datalink packest, reconstruct the SPP packets
:param datalink_list:
:return:
"""
spp_packet_list = []
segmented_packet_list = []
# TODO : Support reordering of packets, right now it assumes that packets must come in order
reordered_datalink_list = [None] * len(datalink_list)
for packet in datalink_list:
reordered_datalink_list[packet.frame_seq_num] = packet
for packet in reordered_datalink_list:
# filter out packets that do not match spacecraft_id, virtual_channel_id and map_id
if packet.spacecraft_id != self.spacecraft_id or packet.virtual_channel_id != self.virtual_channel_id or \
packet.map_id != self.map_id:
continue
# handle different case scenarios
if packet.seq_flags == SegmentHeaderSequenceFlags.UNSEGMENTED:
spp_packet_list.append(SpacePacket.from_bytes(packet.data))
elif packet.seq_flags == SegmentHeaderSequenceFlags.SEGMENT_FIRST:
segmented_packet_list = [packet]
elif packet.seq_flags == SegmentHeaderSequenceFlags.SEGMENT_CONTINUATION:
assert (len(segmented_packet_list) > 0)
segmented_packet_list.append(packet)
elif packet.seq_flags == SegmentHeaderSequenceFlags.SEGMENT_LAST:
segmented_packet_list.append(packet)
# receive the last segmented packet, reconstruct the packet here
data_bytestream = b''
for segmented_packet in segmented_packet_list:
data_bytestream += segmented_packet.data
segmented_packet_list = []
spp_packet_list.append(SpacePacket.from_bytes(data_bytestream))
else:
raise RuntimeError("Sequence Flag {} not implemented".format(packet.seq_flags))
return spp_packet_list
def test_space_packet_from_bytes():
"""
Test deserialization of space packets
:return:
"""
byte_sequence = b'\x05\x39\xc0\x11\x00\x04\xde\xad\xbe\xef'
expected_space_packet = SpacePacket(
ccsds_version=0,
packet_type=SpacePacketType.TELECOMMAND,
apid=TEST_APID_VAL,
seq_flags=SpacePacketSequenceFlags.UNSEGMENTED,
packet_seq_count=17,
data=b'\xde\xad\xbe\xef',
sec_hdr_flag=False
)
space_packet = SpacePacket.from_bytes(byte_sequence)
assert(space_packet == expected_space_packet)