New ais encoded/decoder for message 18 and 24

ais-stream/decode.py

@@ -2,7 +2,9 @@
 import base64
 
 from config import load_config
-from ais_tools import aivdm
+from ais_tools.aivdm import AIVDM
+
+decoder = AIVDM()
 
 
 def handle_event(event, context, pubsub_client):
@@ -19,7 +21,7 @@ def handle_event(event, context, pubsub_client):
             message_in['source'] = config['DEFAULT_SOURCE']
 
         message_out = message_in
-        message_out.update(aivdm.safe_decode(message_in['nmea']))
+        message_out.update(decoder.safe_decode(message_in['nmea']))
 
         data_out = json.dumps(message_out).encode("utf-8")
         pubsub_client.publish(config['DECODE_PUBSUB_TOPIC'], data=data_out, source=message_out['source'])

ais_tools/ais.py

@@ -0,0 +1,43 @@
+from ais_tools.transcode import DecodeError
+from ais_tools.transcode import MessageTranscoder
+from ais_tools.transcode import UintTranscoder as Uint
+from ais_tools.transcode import bits_to_nmea
+from ais_tools.transcode import nmea_to_bits
+from ais_tools.transcode import byte_align
+from ais_tools import ais18
+from ais_tools import ais24
+from ais_tools import ais25
+
+
+message_types = {
+    18: [ais18.AIS18Transcoder()],
+    24: [ais24.AIS24Transcoder()],
+    25: [ais25.AIS25Transcoder()],
+}
+
+
+class AISMessageTypeTranscoder(MessageTranscoder):
+
+    def get_fields(self, message=None):
+        msg_type = message.get('id')
+        if msg_type not in message_types:
+            raise DecodeError('AIS: Unknown message type {}'.format(msg_type))
+        fields = message_types.get(msg_type, [])
+        return fields
+
+
+ais_fields = [
+    Uint(name='id', nbits=6, default=0),
+    AISMessageTypeTranscoder(),
+]
+
+
+class AISMessageTranscoder(MessageTranscoder):
+    def __init__(self):
+        super().__init__(ais_fields)
+
+    def encode_nmea(self, message):
+        return bits_to_nmea(byte_align(self.encode(message)))
+
+    def decode_nmea(self, body, pad=0):
+        return self.decode(nmea_to_bits(body, pad))

ais_tools/ais18.py

@@ -0,0 +1,103 @@
+from ais_tools import transcode
+from ais_tools.transcode import DecodeError
+from ais_tools.transcode import BitsTranscoder
+from ais_tools.transcode import UintTranscoder as Uint
+from ais_tools.transcode import Uint10Transcoder as Uint10
+from ais_tools.transcode import LatLonTranscoder as LatLon
+
+
+class AIS18Transcoder(transcode.MessageTranscoder):
+    def __init__(self):
+        super().__init__(ais18_fields)
+
+
+class AIS18CommState(transcode.MessageTranscoder):
+    def get_fields(self, message=None):
+        unit_flag = message.get('unit_flag', 0)
+        commstate_flag = message.get('commstate_flag', 0)
+
+        if unit_flag == 0:
+            if commstate_flag == 0:
+                return ais18_commstate_SOTDMA
+            else:
+                return ais18_commstate_ITDMA
+        else:
+            return ais18_commstate_CS
+
+
+class AIS18CommStateSOTDMA(transcode.MessageTranscoder):
+    def get_fields(self, message=None):
+        slot_timeout = message.get('slot_timeout', 0)
+        if slot_timeout == 0:
+            return ais18_commstate_SOTDMA_timeout_0
+        elif slot_timeout == 1:
+            return ais18_commstate_SOTDMA_timeout_1
+        elif slot_timeout in (2, 4, 6):
+            return ais18_commstate_SOTDMA_timeout_2_4_6
+        elif slot_timeout in (3, 5, 7):
+            return ais18_commstate_SOTDMA_timeout_3_5_7
+        else:
+            raise DecodeError('AIS18: unknown slot_timeout value {}'.format(slot_timeout))
+
+
+ais18_fields = [
+    Uint(name='repeat_indicator', nbits=2),
+    Uint(name='mmsi', nbits=30),
+    Uint(name='spare', nbits=8),
+    Uint10(name='sog', nbits=10, default=102.3),
+    Uint(name='position_accuracy', nbits=1),
+    LatLon(name='x', nbits=28, default=181),
+    LatLon(name='y', nbits=27, default=91),
+    Uint10(name='cog', nbits=12, default=360),
+    Uint(name='true_heading', nbits=9, default=511),
+    Uint(name='timestamp', nbits=6, default=60),
+    Uint(name='spare2', nbits=2),
+    Uint(name='unit_flag', nbits=1),
+    Uint(name='display_flag', nbits=1),
+    Uint(name='dsc_flag', nbits=1),
+    Uint(name='band_flag', nbits=1),
+    Uint(name='m22_flag', nbits=1),
+    Uint(name='mode_flag', nbits=1),
+    Uint(name='raim', nbits=1),
+    Uint(name='commstate_flag', nbits=1),
+    AIS18CommState()
+]
+
+ais18_commstate_CS = [
+    BitsTranscoder(name='commstate', nbits=19, default='1100000000000000110'),
+]
+
+ais18_commstate_ITDMA = [
+    Uint(name='sync_state', nbits=2),
+    Uint(name='slot_increment', nbits=13),
+    Uint(name='slots_to_allocate', nbits=3),
+    Uint(name='keep_flag', nbits=1),
+]
+
+ais18_commstate_SOTDMA = [
+    Uint(name='sync_state', nbits=2),
+    Uint(name='slot_timeout', nbits=3),
+    AIS18CommStateSOTDMA()
+]
+
+ais18_commstate_SOTDMA_timeout_0 = [
+    Uint(name='slot_offset', nbits=14),
+]
+
+ais18_commstate_SOTDMA_timeout_1 = [
+    Uint(name='utc_hour', nbits=5),
+    Uint(name='utc_min', nbits=7),
+    Uint(name='utc_spare', nbits=2),
+]
+
+ais18_commstate_SOTDMA_timeout_2_4_6 = [
+    Uint(name='slot_number', nbits=14),
+]
+
+ais18_commstate_SOTDMA_timeout_3_5_7 = [
+    Uint(name='received_stations', nbits=14),
+]
+
+
+
+

ais_tools/ais24.py

@@ -0,0 +1,101 @@
+from ais_tools import transcode
+from ais_tools.transcode import MessageTranscoder as Message
+from ais_tools.transcode import DynamicTranscoder
+from ais_tools.transcode import DecodeError
+from ais_tools.transcode import UintTranscoder as Uint
+from ais_tools.transcode import ASCII6Transcoder as ASCII6
+
+
+class AIS24Transcoder(Message):
+    def __init__(self):
+        super().__init__(ais24_fields)
+
+
+class AIS24PartAB(Message):
+    def get_fields(self, message=None):
+        part_num = message.get('part_num', 0)
+        if part_num == 0:
+            return ais24_part_A_fields
+        elif part_num == 1:
+            return ais24_part_B_fields
+        else:
+            raise DecodeError('AIS24: unknown part number {}'.format(part_num))
+
+
+class VendorID(DynamicTranscoder):
+    def __init__(self):
+        self.vendorid_1371_2 = Message(ais24_vendorid_ITU_R_1371_2)
+        self.vendorid_1371_4 = Message(ais24_vendorid_ITU_R_1371_4)
+
+    def encoder(self, message):
+        if 'vendor_id' in message:
+            return self.vendorid_1371_2
+        else:
+            return self.vendorid_1371_4
+
+    def decoders(self, message):
+        return [self.vendorid_1371_2, self.vendorid_1371_4]
+
+
+class DimensionOrMothership(Message):
+    def __init__(self):
+        super().__init__()
+        self.shipDimension = Message(ais24_part_B_dimension_fields)
+        self.mothershipMMSI = Message(ais24_part_B_mothership_fields)
+
+    def get_fields(self, message=None):
+        mmsi = message.get('id')
+        if mmsi // 10000000 == 98:
+            return [self.mothershipMMSI]
+        else:
+            return [self.shipDimension]
+
+
+# COMMON FIELDS
+ais24_fields = [
+    Uint(name='repeat_indicator', nbits=2),
+    Uint(name='mmsi', nbits=30),
+    Uint(name='part_num', nbits=2),
+    AIS24PartAB()
+]
+
+# PART A
+ais24_part_A_fields = [
+    ASCII6(name='name', nbits=120),
+]
+
+# PART B
+ais24_vendorid_ITU_R_1371_2 =[
+    ASCII6(name='vendor_id', nbits=42, default='@@@@@@@'),
+]
+
+ais24_vendorid_ITU_R_1371_4 =[
+    ASCII6(name='vendor_id_1371_4', nbits=18, default='@@@'),
+    Uint(name='vendor_model', nbits=4),
+    Uint(name='vendor_serial', nbits=20),
+]
+
+ais24_part_B_dimension_fields = [
+    Uint(name='dim_a', nbits=9),
+    Uint(name='dim_b', nbits=9),
+    Uint(name='dim_c', nbits=6),
+    Uint(name='dim_d', nbits=6),
+]
+
+ais24_part_B_mothership_fields = [
+    Uint(name='mothership_mmsi', nbits=30),
+]
+
+ais24_part_B_fields = [
+    Uint(name='type_and_cargo', nbits=8),
+    VendorID(),
+    ASCII6(name='callsign', nbits=42, default='@@@@@@@'),
+    DimensionOrMothership(),
+    Uint(name='gps_type', nbits=4),
+    Uint(name='spare', nbits=2),
+]
+
+
+
+
+

ais_tools/ais25.py

@@ -0,0 +1,47 @@
+from ais_tools import transcode
+from ais_tools.transcode import DecodeError
+from ais_tools.transcode import UintTranscoder as Uint
+from ais_tools.transcode import ASCII6Transcoder as ASCII6
+from ais_tools.transcode import VariableLengthASCII6Transcoder as VarASCII6
+
+# Using this coding  http://www.e-navigation.nl/content/text-using-6-bit-ascii-1
+
+
+class AIS25Transcoder(transcode.MessageTranscoder):
+    def __init__(self):
+        super().__init__(ais25_fields)
+
+
+class AIS25Destination(transcode.MessageTranscoder):
+    def get_fields(self, message=None):
+        addressed = message.get('addressed', 0)
+        if addressed:
+            return ais25_destination_fields
+        else:
+            return []
+
+
+ais25_fields = [
+    Uint(name='repeat_indicator', nbits=2),
+    Uint(name='mmsi', nbits=30),
+    Uint(name='part_num', nbits=2),
+    Uint(name='addressed', nbits=1),
+    Uint(name='use_app_id', nbits=1),
+    AIS25Destination(),
+    Uint(name='dac', nbits=10, default=1),
+    Uint(name='fi', nbits=6),
+    Uint(name='text_seq', nbits=11),
+    VarASCII6(name='text', default='')
+]
+
+ais25_destination_fields = [
+    Uint(name='dest_mmsi', nbits=30),
+    Uint(name='spare', nbits=2),
+]
+
+
+
+
+
+
+