Correctly limit the maximum message size and allow empty channels (#29)

docs/conversion.rst

@@ -0,0 +1,22 @@
+############
+Conversion
+############
+
+The following fields are directly converted to floats without **ANY** conversion:
+
+1. Turn
+2. Speed (speed over ground)
+3. Longitude
+4. Latitude
+5. Course (Course over ground)
+6. `to_bow`, `to_stern`, `to_port`, `to_starboard`
+7. `ne_lon`, `ne_lat`, `sw_lon`, `sw_lat`
+
+All of these values are native ``floats``. This means that you need to convert the value into the format of choice.
+
+A common use case is to convert the values into strings, with fixed sized precision::
+
+    content = decode_msg("!AIVDO,1,1,,,B>qc:003wk?8mP=18D3Q3wgTiT;T,0*13")
+    print(content["speed"])                         #=> 102.30000000000001
+    print(format(content["speed"], ".1f"))          #=> 102.3
+    print(f"{content['speed'] :.6f}")               #=> 102.300000

docs/usage.rst

@@ -1,10 +1,11 @@
-############
+################
 Usage examples
-############
+################
 
 .. toctree::
    :maxdepth: 1
 
    examples/single
    examples/file
    examples/sockets
+   conversion

pyais/messages.py

@@ -45,11 +45,6 @@ def validate_message(msg: bytes) -> None:
             "Sentence number is empty!"
         )
 
-    if not values[4]:
-        raise InvalidNMEAMessageException(
-            "The AIS channel (A or B) is empty."
-        )
-
     if not values[5]:
         raise InvalidNMEAMessageException(
             "The NMEA message body (payload) is empty."
@@ -95,10 +90,10 @@ def validate_message(msg: bytes) -> None:
                 "Invalid  sequential message ID. No Number."
             )
 
-    # It should not have more than 82 chars (including starting $ or ! and <LF>)
-    if len(msg) > 82:
+    # It should not have more than 82 chars of payload
+    if len(values[5]) > 82:
         raise InvalidNMEAMessageException(
-            f"{msg.decode('utf-8')} has more than 82 characters."
+            f"{msg.decode('utf-8')} has more than 82 characters of payload."
         )
 
     # Only encapsulated messages are currently supported

tests/test_ais.py

@@ -1,5 +1,6 @@
 import unittest
 
+from pyais import decode_msg
 from pyais.ais_types import AISType
 from pyais.constants import ManeuverIndicator, NavigationStatus, ShipType, NavAid, EpfdType
 from pyais.exceptions import UnknownMessageException
@@ -583,3 +584,50 @@ def test_fail_silently(self):
     "decoded": {}
 }"""
         self.assertEqual(nmea.decode().to_json(), text)
+
+    def test_empty_channel(self):
+        msg = b"!AIVDO,1,1,,,B>qc:003wk?8mP=18D3Q3wgTiT;T,0*13"
+
+        self.assertEqual(NMEAMessage(msg).channel, "")
+
+        content = decode_msg(msg)
+        self.assertEqual(content["type"], 18)
+        self.assertEqual(content["repeat"], 0)
+        self.assertEqual(content["mmsi"], "1000000000")
+        self.assertEqual(format(content["speed"], ".1f"), "102.3")
+        self.assertEqual(content["accuracy"], 0)
+        self.assertEqual(str(content["lon"]), "181.0")
+        self.assertEqual(str(content["lat"]), "91.0")
+        self.assertEqual(str(content["course"]), "360.0")
+        self.assertEqual(content["heading"], 511)
+        self.assertEqual(content["second"], 31)
+        self.assertEqual(content["regional"], 0)
+        self.assertEqual(content["cs"], 1)
+        self.assertEqual(content["display"], 0)
+        self.assertEqual(content["band"], 1)
+        self.assertEqual(content["radio"], 410340)
+
+    def test_msg_with_more_that_82_chars_payload(self):
+        content = decode_msg(
+            "!AIVDM,1,1,,B,53ktrJ82>ia4=50<0020<5=@Dhv0t8T@u<0000001PV854Si0;mR@CPH13p0hDm1C3h0000,2*35"
+        )
+
+        self.assertEqual(content["type"], 5)
+        self.assertEqual(content["mmsi"], "255801960")
+        self.assertEqual(content["repeat"], 0)
+        self.assertEqual(content["ais_version"], 2)
+        self.assertEqual(content["imo"], 9356945)
+        self.assertEqual(content["callsign"], "CQPC")
+        self.assertEqual(content["shipname"], "CASTELO OBIDOS")
+        self.assertEqual(content["shiptype"], ShipType.NotAvailable)
+        self.assertEqual(content["to_bow"], 12)
+        self.assertEqual(content["to_stern"], 38)
+        self.assertEqual(content["to_port"], 8)
+        self.assertEqual(content["to_starboard"], 5)
+        self.assertEqual(content["epfd"], EpfdType.GPS)
+        self.assertEqual(content["month"], 2)
+        self.assertEqual(content["day"], 7)
+        self.assertEqual(content["hour"], 17)
+        self.assertEqual(content["minute"], 0)
+        self.assertEqual(content["draught"], 4.7)
+        self.assertEqual(content["destination"], "VIANA DO CASTELO")

tests/test_decode_raw.py

@@ -41,7 +41,6 @@ def should_raise(msg):
         should_raise(",1,1,,A,403Ovl@000Htt<tSF0l4Q@100`Pq,0*28")
         should_raise("!AIVDM,,1,,A,403Ovl@000Htt<tSF0l4Q@100`Pq,0*28")
         should_raise("!AIVDM,1,,,A,403Ovl@000Htt<tSF0l4Q@100`Pq,0*28")
-        should_raise("!AIVDM,1,1,,,403Ovl@000Htt<tSF0l4Q@100`Pq,0*28")
         should_raise("!AIVDM,1,1,,A,,0*28")
         should_raise("!AIVDM,1,1,,A,403Ovl@000Htt<tSF0l4Q@100`Pq,")