Add virtual interface.

Author: christiansandberg

README

@@ -85,6 +85,13 @@ IXXAT
 The Linux ECI SDK is currently unsupported.
 On Linux some devices are supported with socketcan.
 
+virtual
+~~~~~~~
+
+A virtual CAN bus that can be used for automatic tests. Any Bus instances
+connecting to the same channel (in the same python program) will get each
+others messages.
+
 Installation
 ------------
 

can/interfaces/interface.py

@@ -53,6 +53,9 @@ def __new__(cls, other, channel=None, *args, **kwargs):
         elif interface == 'ixxat':
             from can.interfaces.ixxat import IXXATBus
             cls = IXXATBus
+        elif interface == 'virtual':
+            from can.interfaces.virtual import VirtualBus
+            cls = VirtualBus
         else:
             raise NotImplementedError("CAN interface '{}' not supported".format(interface))
 

can/interfaces/virtual.py

@@ -0,0 +1,59 @@
+# -*- coding: utf-8 -*-
+
+"""
+This module implements an OS and hardware independent
+virtual CAN interface for testing purposes.
+
+Any VirtualBus instances connecting to the same channel
+will get the same messages. Sent messages will also be
+echoed back to the same bus.
+"""
+
+import logging
+import time
+try:
+    import queue as queue
+except ImportError:
+    import Queue as queue
+from can.bus import BusABC
+
+
+logger = logging.getLogger(__name__)
+logger.setLevel(logging.DEBUG)
+
+
+# Channels are lists of queues, one for each connection
+channels = {}
+
+class VirtualBus(BusABC):
+    """Virtual CAN bus using an internal message queue for testing."""
+
+    def __init__(self, channel=None, **config):
+        self.channel_info = 'Virtual bus channel %s' % channel
+
+        # Create a new channel if one does not exist
+        if channel not in channels:
+            channels[channel] = []
+
+        self.queue = queue.Queue()
+        self.channel = channels[channel]
+        self.channel.append(self.queue)
+
+    def recv(self, timeout=None):
+        try:
+            msg = self.queue.get(block=bool(timeout), timeout=timeout)
+        except queue.Empty:
+            return None
+
+        logger.log(9, 'Received message:\n%s', msg)
+        return msg
+
+    def send(self, msg):
+        msg.timestamp = time.time()
+        # Add message to all listening on this channel
+        for bus_queue in self.channel:
+            bus_queue.put(msg)
+        logger.log(9, 'Transmitted message:\n%s', msg)
+
+    def shutdown(self):
+        self.channel.remove(self.queue)

doc/interfaces.rst

@@ -11,5 +11,6 @@ Found under ``can.interfaces`` are the implementations for each backend:
     serial
     ixxat
     pcan
+    virtual
 
 These interfaces define the low level interface to the physical controller area network.

doc/virtual.rst

@@ -0,0 +1,21 @@
+Virtual
+=======
+
+The virtual interface can be used as a way to write OS and driver independent
+tests.
+
+Bus instances connecting to the same channel will share the same messages.
+
+
+.. code-block:: python
+    
+    import can
+
+    bus1 = can.interface.Bus('test', bustype='virtual')
+    bus2 = can.interface.Bus('test', bustype='virtual')
+
+    msg1 = can.Message(arbitration_id=0xabcde, data=[1,2,3])
+    bus1.send(msg1)
+    msg2 = bus2.recv()
+
+    assert msg1 == msg2