Add in simple multiplexing for dbc (#816)

* test: add in two new unittests

* test: remove unneeded test

* feat: add in handling for simple multiplexing

* feat: add in more logic

* docs: update description of multiplex_signals

---------

Co-authored-by: Eduard Bröcker <[email protected]>

Author: khauersp

src/canmatrix/canmatrix.py

@@ -1671,6 +1671,17 @@ def compress(self):
                         gap_found = True
                         break
 
+    def multiplex_signals(self):
+        """Assign multiplexer to signals. When a multiplexor is in the frame."""
+        multiplexor = self.get_multiplexer
+        if multiplexor is None:
+            return
+
+        for signal in self.signals:
+            if signal.is_multiplexer or (signal.muxer_for_signal is not None):
+                continue
+            signal.muxer_for_signal = multiplexor.name
+            signal.mux_val = signal.multiplex
 
     def __str__(self):  # type: () -> str
         """Represent the frame by its name only."""

src/canmatrix/formats/dbc.py

@@ -599,9 +599,11 @@ def add_frame_by_id(new_frame):  # type: (canmatrix.Frame) -> None
                     multiplex = temp.group(2)  # type: str
 
                     is_complex_multiplexed = False
+                    is_multiplexer = False
 
                     if multiplex == 'M':
                         multiplex = 'Multiplexor'
+                        is_multiplexer = True
                     elif multiplex.endswith('M'):
                         is_complex_multiplexed = True
                         multiplex = multiplex[:-1]
@@ -632,7 +634,7 @@ def add_frame_by_id(new_frame):  # type: (canmatrix.Frame) -> None
                         **extras
                     )
 
-                    if is_complex_multiplexed:
+                    if is_complex_multiplexed or is_multiplexer:
                         temp_signal.is_multiplexer = True
                         temp_signal.multiplex = 'Multiplexor'
 
@@ -989,6 +991,7 @@ def add_frame_by_id(new_frame):  # type: (canmatrix.Frame) -> None
 
     db.enum_attribs_to_values()
     for frame in db.frames:
+        frame.multiplex_signals()
         if "_FD" in frame.attributes.get("VFrameFormat", ""):
             frame.is_fd = True
         if "J1939PG" in frame.attributes.get("VFrameFormat", ""):

tests/test_dbc.py

@@ -339,6 +339,20 @@ def test_j1939_frametype():
     matrix = canmatrix.formats.dbc.load(dbc, dbcImportEncoding="utf8")
     assert matrix.frames[0].is_j1939 == False
 
+def test_multiplex_frame():
+    dbc = io.BytesIO(textwrap.dedent(u'''\
+    BU_: someOtherEcu
+    
+    BO_ 123 someFrame: 8 someOtherEcu
+     SG_ someSignal m2 : 8|8@1+ (1,0) [0|9] ""  CCL_TEST
+     SG_ someOtherSignal m1 : 8|8@0+ (1,0) [0|9] ""  CCL_TEST
+     SG_ someMultiplexor M : 0|8@1+ (1,0) [0|2] ""  CCL_TEST
+    ''').encode('utf-8'))
+    matrix = canmatrix.formats.dbc.load(dbc, dbcImportEncoding="utf8")
+    assert matrix.frames[0].is_multiplexed
+
+    assert matrix.frames[0].signal_by_name("someSignal").muxer_for_signal == "someMultiplexor"
+
 
 def test_attributes_with_spaces_before_semicolumn():
     dbc = io.BytesIO(textwrap.dedent(u'''\