Add preserve timestamps to virtual

Add an option to virtual interfaces to preserve message timestamps
on transmissions. This is useful in test setups fed by log files.

Author: simontegelid

can/interfaces/virtual.py

@@ -59,6 +59,7 @@ def __init__(
         channel: Any = None,
         receive_own_messages: bool = False,
         rx_queue_size: int = 0,
+        preserve_timestamps: bool = False,
         **kwargs: Any,
     ) -> None:
         super().__init__(
@@ -69,6 +70,7 @@ def __init__(
         self.channel_id = channel
         self.channel_info = f"Virtual bus channel {self.channel_id}"
         self.receive_own_messages = receive_own_messages
+        self.preserve_timestamps = preserve_timestamps
         self._open = True
 
         with channels_lock:
@@ -103,7 +105,7 @@ def _recv_internal(
     def send(self, msg: Message, timeout: Optional[float] = None) -> None:
         self._check_if_open()
 
-        timestamp = time.time()
+        timestamp = msg.timestamp if self.preserve_timestamps else time.time()
         # Add message to all listening on this channel
         all_sent = True
         for bus_queue in self.channel:

doc/interfaces/virtual.rst

@@ -85,7 +85,7 @@ Example
 -------
 
 .. code-block:: python
-    
+
     import can
 
     bus1 = can.interface.Bus('test', bustype='virtual')
@@ -100,6 +100,33 @@ Example
     assert msg1.data == msg2.data
     assert msg1.timestamp != msg2.timestamp
 
+.. code-block:: python
+
+    import can
+
+    bus1 = can.interface.Bus('test', bustype='virtual', preserve_timestamps=True)
+    bus2 = can.interface.Bus('test', bustype='virtual')
+
+    msg1 = can.Message(timestamp=1639740470.051948, arbitration_id=0xabcde, data=[1,2,3])
+
+    # Messages sent on bus1 will have their timestamps preserved when received
+    # on bus2
+    bus1.send(msg1)
+    msg2 = bus2.recv()
+
+    assert msg1.arbitration_id == msg2.arbitration_id
+    assert msg1.data == msg2.data
+    assert msg1.timestamp == msg2.timestamp
+
+    # Messages sent on bus2 will not have their timestamps preserved when
+    # received on bus1
+    bus2.send(msg1)
+    msg3 = bus1.recv()
+
+    assert msg1.arbitration_id == msg3.arbitration_id
+    assert msg1.data == msg3.data
+    assert msg1.timestamp != msg3.timestamp
+
 
 Bus Class Documentation
 -----------------------

test/test_interface_virtual.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python
+# coding: utf-8
+
+"""
+This module tests :meth:`can.interface.virtual`.
+"""
+
+import unittest
+
+from can import Bus, Message
+
+EXAMPLE_MSG1 = Message(timestamp=1639739471.5565314, arbitration_id=0x481, data=b"\x01")
+
+
+class TestMessageFiltering(unittest.TestCase):
+    def setUp(self):
+        self.node1 = Bus("test", bustype="virtual", preserve_timestamps=True)
+        self.node2 = Bus("test", bustype="virtual")
+
+    def tearDown(self):
+        self.node1.shutdown()
+        self.node2.shutdown()
+
+    def test_sendmsg(self):
+        self.node2.send(EXAMPLE_MSG1)
+        r = self.node1.recv(0.1)
+        assert r.timestamp != EXAMPLE_MSG1.timestamp
+        assert r.arbitration_id == EXAMPLE_MSG1.arbitration_id
+        assert r.data == EXAMPLE_MSG1.data
+
+    def test_sendmsg_preserve_timestamp(self):
+        self.node1.send(EXAMPLE_MSG1)
+        r = self.node2.recv(0.1)
+        assert r.timestamp == EXAMPLE_MSG1.timestamp
+        assert r.arbitration_id == EXAMPLE_MSG1.arbitration_id
+        assert r.data == EXAMPLE_MSG1.data
+
+
+if __name__ == "__main__":
+    unittest.main()