adding absolute timestamp to ASC reader

can/io/asc.py

@@ -31,14 +31,15 @@ class ASCReader(BaseIOHandler):
     """
     Iterator of CAN messages from a ASC logging file. Meta data (comments,
     bus statistics, J1939 Transport Protocol messages) is ignored.
-
-    TODO: turn relative timestamps back to absolute form
     """
 
+    FORMAT_START_OF_FILE_DATE = "%a %b %d %I:%M:%S.%f %p %Y"
+
     def __init__(
         self,
         file: Union[typechecking.FileLike, typechecking.StringPathLike],
         base: str = "hex",
+        relative_timestamp: bool = True,
     ) -> None:
         """
         :param file: a path-like object or as file-like object to read from
@@ -47,14 +48,19 @@ def __init__(
         :param base: Select the base(hex or dec) of id and data.
                      If the header of the asc file contains base information,
                      this value will be overwritten. Default "hex".
+        :param relative_timestamp: Select whether the timestamps are
+                     `relative` (starting at 0.0) or `absolute` (starting at
+                     the system time). Default `True = relative`.
         """
         super().__init__(file, mode="r")
 
         if not self.file:
             raise ValueError("The given file cannot be None")
         self.base = base
         self._converted_base = self._check_base(base)
+        self.relative_timestamp = relative_timestamp
         self.date = None
+        # TODO - what is this used for? The ASC Writer only prints `absolute`
         self.timestamps_format = None
         self.internal_events_logged = None
 
@@ -74,6 +80,22 @@ def _extract_header(self):
                 self.timestamps_format = timestamp_format
             elif lower_case.endswith("internal events logged"):
                 self.internal_events_logged = not lower_case.startswith("no")
+            elif lower_case.startswith("// version"):
+                # the test files include `// version 9.0.0` - not sure what this is
+                continue
+            # grab absolute timestamp
+            elif lower_case.startswith("begin triggerblock"):
+                try:
+                    _, _, start_time = lower_case.split(None, 2)
+                    start_time = datetime.strptime(
+                        start_time, self.FORMAT_START_OF_FILE_DATE
+                    ).timestamp()
+                except ValueError:
+                    start_time = 0.0
+                if self.relative_timestamp:
+                    self.start_time = 0.0
+                else:
+                    self.start_time = start_time
                 # Currently the last line in the header which is parsed
                 break
             else:
@@ -191,7 +213,7 @@ def __iter__(self) -> Generator[Message, None, None]:
             msg_kwargs = {}
             try:
                 timestamp, channel, rest_of_message = temp.split(None, 2)
-                timestamp = float(timestamp)
+                timestamp = float(timestamp) + self.start_time
                 msg_kwargs["timestamp"] = timestamp
                 if channel == "CANFD":
                     msg_kwargs["is_fd"] = True

test/data/test_CanMessage.asc

@@ -2,7 +2,7 @@ date Sam Sep 30 15:06:13.191 2017
 base hex  timestamps absolute
 internal events logged
 // version 9.0.0
-Begin Triggerblock Sam Sep 30 15:06:13.191 2017
+Begin Triggerblock Sat Sep 30 10:06:13.191 PM 2017
    0.000000 Start of measurement
      2.5010 2   C8             Tx   d 8 09 08 07 06 05 04 03 02
   17.876708 1  6F9             Rx   d 8 05 0C 00 00 00 00 00 00  Length = 240015 BitCount = 124 ID = 1785

test/logformats_test.py

@@ -20,6 +20,7 @@
 import os
 from abc import abstractmethod, ABCMeta
 from itertools import zip_longest
+from datetime import datetime
 
 import can
 
@@ -364,6 +365,8 @@ def assertIncludesComments(self, filename):
 class TestAscFileFormat(ReaderWriterTest):
     """Tests can.ASCWriter and can.ASCReader"""
 
+    FORMAT_START_OF_FILE_DATE = "%a %b %d %I:%M:%S.%f %p %Y"
+
     def _setup_instance(self):
         super()._setup_instance_helper(
             can.ASCWriter,
@@ -374,11 +377,39 @@ def _setup_instance(self):
             adds_default_channel=0,
         )
 
-    def _read_log_file(self, filename):
+    def _read_log_file(self, filename, **kwargs):
         logfile = os.path.join(os.path.dirname(__file__), "data", filename)
-        with can.ASCReader(logfile) as reader:
+        with can.ASCReader(logfile, **kwargs) as reader:
             return list(reader)
 
+    def test_absolute_time(self):
+        time_from_file = "Sat Sep 30 10:06:13.191 PM 2017"
+        start_time = datetime.strptime(
+            time_from_file, self.FORMAT_START_OF_FILE_DATE
+        ).timestamp()
+
+        expected_messages = [
+            can.Message(
+                timestamp=2.5010 + start_time,
+                arbitration_id=0xC8,
+                is_extended_id=False,
+                is_rx=False,
+                channel=1,
+                dlc=8,
+                data=[9, 8, 7, 6, 5, 4, 3, 2],
+            ),
+            can.Message(
+                timestamp=17.876708 + start_time,
+                arbitration_id=0x6F9,
+                is_extended_id=False,
+                channel=0,
+                dlc=0x8,
+                data=[5, 0xC, 0, 0, 0, 0, 0, 0],
+            ),
+        ]
+        actual = self._read_log_file("test_CanMessage.asc", relative_timestamp=False)
+        self.assertMessagesEqual(actual, expected_messages)
+
     def test_can_message(self):
         expected_messages = [
             can.Message(