Implement en- and decoding of SYSTEM parameters

odxtools/parameters/systemparameter.py

@@ -1,19 +1,29 @@
 # SPDX-License-Identifier: MIT
+import getpass
 from dataclasses import dataclass
+from datetime import datetime
 from typing import List, Optional
 from xml.etree import ElementTree
 
 from typing_extensions import override
 
-from ..decodestate import DecodeState
 from ..encodestate import EncodeState
-from ..exceptions import odxrequire
+from ..exceptions import odxraise, odxrequire
 from ..odxlink import OdxDocFragment
 from ..odxtypes import ParameterValue
 from ..utils import dataclass_fields_asdict
 from .parameter import ParameterType
 from .parameterwithdop import ParameterWithDOP
 
+# The SYSTEM parameter types mandated by the ODX 2.2 standard. Users
+# are free to specify additional types, but these must be handled
+# (cf. table 5 in section 7.3.5.4 of the ASAM ODX 2.2 specification
+# document.)
+PREDEFINED_SYSPARAM_VALUES = [
+    "TIMESTAMP", "SECOND", "MINUTE", "HOUR", "TIMEZONE", "DAY", "WEEK", "MONTH", "YEAR", "CENTURY",
+    "TESTERID", "USERID"
+]
+
 
 @dataclass
 class SystemParameter(ParameterWithDOP):
@@ -38,18 +48,51 @@ def parameter_type(self) -> ParameterType:
     @property
     @override
     def is_required(self) -> bool:
-        raise NotImplementedError("SystemParameter.is_required is not implemented yet.")
+        # if a SYSTEM parameter is not specified explicitly, its value
+        # can be determined from the operating system if it is type is
+        # predefined
+        return self.sysparam not in PREDEFINED_SYSPARAM_VALUES
 
     @property
     @override
     def is_settable(self) -> bool:
-        raise NotImplementedError("SystemParameter.is_settable is not implemented yet.")
+        return True
 
     @override
     def _encode_positioned_into_pdu(self, physical_value: Optional[ParameterValue],
                                     encode_state: EncodeState) -> None:
-        raise NotImplementedError("Encoding a SystemParameter is not implemented yet.")
+        if physical_value is None:
+            # determine the value to be encoded automatically
+            now = datetime.now()
+            if self.sysparam == "TIMESTAMP":
+                physical_value = round(now.timestamp() * 1000).to_bytes(8, "big")
+            elif self.sysparam == "SECOND":
+                physical_value = now.second
+            elif self.sysparam == "MINUTE":
+                physical_value = now.minute
+            elif self.sysparam == "HOUR":
+                physical_value = now.hour
+            elif self.sysparam == "TIMEZONE":
+                if (utc_offset := now.astimezone().utcoffset()) is not None:
+                    physical_value = utc_offset.seconds // 60
+                else:
+                    physical_value = 0
+            elif self.sysparam == "DAY":
+                physical_value = now.day
+            elif self.sysparam == "WEEK":
+                physical_value = now.isocalendar()[1]
+            elif self.sysparam == "MONTH":
+                physical_value = now.month
+            elif self.sysparam == "YEAR":
+                physical_value = now.year
+            elif self.sysparam == "CENTURY":
+                physical_value = now.year // 100
+            elif self.sysparam == "TESTERID":
+                physical_value = "odxtools".encode("latin1")
+            elif self.sysparam == "USERID":
+                physical_value = getpass.getuser().encode("latin1")
+            else:
+                odxraise(f"Unknown system parameter type '{self.sysparam}'")
+                physical_value = 0
 
-    @override
-    def _decode_positioned_from_pdu(self, decode_state: DecodeState) -> ParameterValue:
-        raise NotImplementedError("Decoding SystemParameter is not implemented yet.")
+        self.dop.encode_into_pdu(physical_value, encode_state=encode_state)

tests/test_encoding.py

@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: MIT
 import unittest
+from datetime import datetime
 from typing import List
 
 from odxtools.compumethods.compuinternaltophys import CompuInternalToPhys
@@ -10,6 +11,7 @@
 from odxtools.compumethods.linearcompumethod import LinearCompuMethod
 from odxtools.database import Database
 from odxtools.dataobjectproperty import DataObjectProperty
+from odxtools.decodestate import DecodeState
 from odxtools.description import Description
 from odxtools.diagdatadictionaryspec import DiagDataDictionarySpec
 from odxtools.diaglayers.diaglayertype import DiagLayerType
@@ -18,6 +20,7 @@
 from odxtools.diagnostictroublecode import DiagnosticTroubleCode
 from odxtools.diagservice import DiagService
 from odxtools.dtcdop import DtcDop
+from odxtools.encodestate import EncodeState
 from odxtools.environmentdata import EnvironmentData
 from odxtools.environmentdatadescription import EnvironmentDataDescription
 from odxtools.exceptions import EncodeError
@@ -27,6 +30,7 @@
 from odxtools.parameters.codedconstparameter import CodedConstParameter
 from odxtools.parameters.nrcconstparameter import NrcConstParameter
 from odxtools.parameters.parameter import Parameter
+from odxtools.parameters.systemparameter import SystemParameter
 from odxtools.parameters.valueparameter import ValueParameter
 from odxtools.physicaltype import PhysicalType, Radix
 from odxtools.request import Request
@@ -410,6 +414,74 @@ def test_encode_nrc_const(self) -> None:
             # NRC-CONST parameters cannot be directly specified
             resp.encode(param2=0xEF, param3=0xAB)
 
+    def test_encode_system_parameter(self) -> None:
+        diag_coded_type = StandardLengthType(
+            base_data_type=DataType.A_UINT32,
+            base_type_encoding=None,
+            bit_length=16,
+            bit_mask=None,
+            is_highlow_byte_order_raw=None,
+            is_condensed_raw=None,
+        )
+        dop = DataObjectProperty(
+            odx_id=OdxLinkId("dop.year", doc_frags),
+            oid=None,
+            short_name="dop_year_sn",
+            long_name=None,
+            description=None,
+            admin_data=None,
+            diag_coded_type=diag_coded_type,
+            physical_type=PhysicalType(DataType.A_UINT32, display_radix=None, precision=None),
+            compu_method=IdenticalCompuMethod(
+                category=CompuCategory.IDENTICAL,
+                compu_internal_to_phys=None,
+                compu_phys_to_internal=None,
+                internal_type=DataType.A_UINT32,
+                physical_type=DataType.A_UINT32),
+            unit_ref=None,
+            sdgs=[],
+            internal_constr=None,
+            physical_constr=None,
+        )
+        param1 = SystemParameter(
+            oid=None,
+            short_name="year_param",
+            long_name=None,
+            description=None,
+            semantic=None,
+            dop_ref=OdxLinkRef.from_id(dop.odx_id),
+            dop_snref=None,
+            sysparam="YEAR",
+            byte_position=0,
+            bit_position=None,
+            sdgs=[],
+        )
+
+        odxlinks = OdxLinkDatabase()
+        odxlinks.update(dop._build_odxlinks())
+
+        param1._resolve_odxlinks(odxlinks)
+
+        encode_state = EncodeState()
+        param1.encode_into_pdu(physical_value=2024, encode_state=encode_state)
+        self.assertEqual(encode_state.coded_message, b'\x07\xe8')
+
+        # test auto-determination of parameter value
+        cur_year = datetime.now().year
+        encode_state = EncodeState()
+        param1.encode_into_pdu(physical_value=None, encode_state=encode_state)
+
+        # there is a (rather theoretical) race condition here: if the
+        # cur_year variable was assigned before the year of the system
+        # date changes (e.g., because it is new-year's eve) and the
+        # encoding was done after that, we will get an incorrect value
+        # here. (good luck exploiting this!)
+        self.assertEqual(encode_state.coded_message, cur_year.to_bytes(2, 'big'))
+
+        # ensure that decoding works as well
+        decode_state = DecodeState(coded_message=encode_state.coded_message)
+        self.assertEqual(param1.decode_from_pdu(decode_state), cur_year)
+
     def test_encode_env_data_desc(self) -> None:
         dct = StandardLengthType(
             base_data_type=DataType.A_UINT32,