closes #136 (#137)

M0r13n · May 10, 2024 · 19d8cc1 · 19d8cc1
1 parent b338dc3
commit 19d8cc1
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diff --git a/pyais/messages.py b/pyais/messages.py
@@ -797,10 +797,14 @@ class CommunicationStateMixin:
     https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1371-1-200108-S!!PDF-E.pdf
     """
 
+    msg_type: int  # Type hint to make mypy happy
     radio: int  # Type hint to make mypy happy
 
     MAX_COMM_STATE_VALUE = 0x7ffff
 
+    SOTDMA_TYPES = (1, 2, 4, 11)
+    SOTDMA_ITDMA_TYPES = (9, 18, 26)
+
     def get_communication_state(self) -> Dict[str, typing.Optional[int]]:
         """Returns information used by the slot allocation algorithm as a dict."""
         result: Dict[str, typing.Optional[int]] = {
@@ -825,13 +829,21 @@ def get_communication_state(self) -> Dict[str, typing.Optional[int]]:
 
     @property
     def is_sotdma(self) -> bool:
-        """The radio status field has it's 20th bit (MSB) set to 0 or has less than 20 bits"""
-        return self.radio <= self.MAX_COMM_STATE_VALUE
+        """Messages of type 1, 2, 4, 11 use SOTDMA or 9, 18, 26 if 20th bit is set."""
+        if self.msg_type in self.SOTDMA_TYPES:
+            return True
+        if self.msg_type in self.SOTDMA_ITDMA_TYPES:
+            return self.radio <= self.MAX_COMM_STATE_VALUE
+        return False
 
     @property
     def is_itdma(self) -> bool:
-        """The radio status field has it's 20th bit (MSB) set to 1"""
-        return self.radio > self.MAX_COMM_STATE_VALUE
+        """Messages of type 3 use ITDMA or 9, 18, 26 if 20th bit is set."""
+        if self.msg_type == 3:
+            return True
+        if self.msg_type in self.SOTDMA_ITDMA_TYPES:
+            return self.radio > self.MAX_COMM_STATE_VALUE
+        return False
 
     @property
     def communication_state_raw(self) -> int:

diff --git a/tests/test_decode.py b/tests/test_decode.py
@@ -1385,6 +1385,14 @@ def test_rot_decode_yields_expected_values(self):
         assert decode(b"!AIVDM,1,1,,A,16:VFv0k0I`KQPpFATG4SgvT40:v,0*7B").turn == -121.0
         assert decode(b"!AIVDM,1,1,,B,16:D3F0:15`5ogh<O?bk>1Dd2L1<,0*0B").turn == 71.0
 
+    def test_sotdma_time_conversion(self):
+        """Prevent regressions for: https://github.com/M0r13n/pyais/pull/135"""
+        decoded = decode('!AIVDM,1,1,,B,133ga6PP0lPPE>4M3G@DpOwTR61p,0*33')
+        cs = decoded.get_communication_state()
+
+        assert cs['utc_hour'] == 16
+        assert cs['utc_minute'] == 30
+
     def test_get_sotdma_comm_state_utc_direct(self):
         msg = "!AIVDM,1,1,,A,13HOI:0P0000VOHLCnHQKwvL05Ip,0*23"
         decoded = decode(msg)
@@ -1457,6 +1465,32 @@ def test_get_sotdma_comm_state_utc_direct_slot_timeout(self):
             },
         )
 
+    def test_is_sotdma_or_itdma(self):
+        """ Verify that messages are correctly identified as either ITDMA or SOTDMA.
+        Details: https://github.com/M0r13n/pyais/issues/136."""
+
+        # 1
+        assert decode(b"!AIVDM,1,1,,A,13n3aW0PCkPJS8>Qhc2<urG02D13,0*18").is_sotdma
+        assert not decode(b"!AIVDM,1,1,,A,13n3aW0PCkPJS8>Qhc2<urG02D13,0*18").is_itdma
+        # 2
+        assert decode(b"!AIVDM,1,1,,A,23aFfl0P00PCR?0MEB@h0?w020S7,0*68").is_sotdma
+        assert not decode(b"!AIVDM,1,1,,A,23aFfl0P00PCR?0MEB@h0?w020S7,0*68").is_itdma
+        # 3
+        assert not decode(b"!AIVDM,1,1,,B,33UTPD5000G<@aTL3:?0010j0000,0*2A").is_sotdma
+        assert decode(b"!AIVDM,1,1,,B,33UTPD5000G<@aTL3:?0010j0000,0*2A").is_itdma
+        # 4
+        assert decode(b"!AIVDM,1,1,,B,4h2=aCAuho;QNOUQrvQ6?a1000S:,0*5D").is_sotdma
+        assert not decode(b"!AIVDM,1,1,,B,4h2=aCAuho;QNOUQrvQ6?a1000S:,0*5D").is_itdma
+        # 9
+        assert decode(b"!AIVDM,1,1,,A,91b55vRCQvOo4PLLww<3cGh20@Br,0*79").is_sotdma
+        assert not decode(b"!AIVDM,1,1,,A,91b55vRCQvOo4PLLww<3cGh20@Br,0*79").is_itdma
+        # 11
+        assert decode(b"!AIVDM,1,1,,A,;03t=KQuho;QM`d:WFAtwnW00000,0*7C").is_sotdma
+        assert not decode(b"!AIVDM,1,1,,A,;03t=KQuho;QM`d:WFAtwnW00000,0*7C").is_itdma
+        # 18
+        assert decode(b" !AIVDM,1,1,,A,B6:a?;03wk?8mP=18D3Q3wP61P06,0*7F").is_sotdma
+        assert not decode(b" !AIVDM,1,1,,A,B6:a?;03wk?8mP=18D3Q3wP61P06,0*7F").is_itdma
+
     def test_get_comm_state_type_18_itdma_base_indirect(self):
         msg = "!AIVDM,1,1,,A,B5NJ;PP005l4ot5Isbl03wsUkP06,0*76"
         decoded = decode(msg)