forked from hardbyte/python-can
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathlistener.py
More file actions
164 lines (118 loc) · 4.57 KB
/
listener.py
File metadata and controls
164 lines (118 loc) · 4.57 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
"""
This module contains the implementation of `can.Listener` and some readers.
"""
from typing import AsyncIterator, Awaitable, Optional
from can.message import Message
from can.bus import BusABC
from abc import ABCMeta, abstractmethod
try:
# Python 3.7
from queue import SimpleQueue, Empty
except ImportError:
# Python 3.0 - 3.6
from queue import Queue as SimpleQueue, Empty # type: ignore
import asyncio
class Listener(metaclass=ABCMeta):
"""The basic listener that can be called directly to handle some
CAN message::
listener = SomeListener()
msg = my_bus.recv()
# now either call
listener(msg)
# or
listener.on_message_received(msg)
# Important to ensure all outputs are flushed
listener.stop()
"""
@abstractmethod
def on_message_received(self, msg: Message):
"""This method is called to handle the given message.
:param msg: the delivered message
"""
def __call__(self, msg: Message):
self.on_message_received(msg)
def on_error(self, exc: Exception):
"""This method is called to handle any exception in the receive thread.
:param exc: The exception causing the thread to stop
"""
def stop(self):
"""
Stop handling new messages, carry out any final tasks to ensure
data is persisted and cleanup any open resources.
Concrete implementations override.
"""
class RedirectReader(Listener):
"""
A RedirectReader sends all received messages to another Bus.
"""
def __init__(self, bus: BusABC):
self.bus = bus
def on_message_received(self, msg: Message):
self.bus.send(msg)
class BufferedReader(Listener):
"""
A BufferedReader is a subclass of :class:`~can.Listener` which implements a
**message buffer**: that is, when the :class:`can.BufferedReader` instance is
notified of a new message it pushes it into a queue of messages waiting to
be serviced. The messages can then be fetched with
:meth:`~can.BufferedReader.get_message`.
Putting in messages after :meth:`~can.BufferedReader.stop` has been called will raise
an exception, see :meth:`~can.BufferedReader.on_message_received`.
:attr bool is_stopped: ``True`` if the reader has been stopped
"""
def __init__(self):
# set to "infinite" size
self.buffer = SimpleQueue()
self.is_stopped = False
def on_message_received(self, msg: Message):
"""Append a message to the buffer.
:raises: BufferError
if the reader has already been stopped
"""
if self.is_stopped:
raise RuntimeError("reader has already been stopped")
else:
self.buffer.put(msg)
def get_message(self, timeout: float = 0.5) -> Optional[Message]:
"""
Attempts to retrieve the latest message received by the instance. If no message is
available it blocks for given timeout or until a message is received, or else
returns None (whichever is shorter). This method does not block after
:meth:`can.BufferedReader.stop` has been called.
:param timeout: The number of seconds to wait for a new message.
:return: the Message if there is one, or None if there is not.
"""
try:
return self.buffer.get(block=not self.is_stopped, timeout=timeout)
except Empty:
return None
def stop(self):
"""Prohibits any more additions to this reader.
"""
self.is_stopped = True
class AsyncBufferedReader(Listener):
"""A message buffer for use with :mod:`asyncio`.
See :ref:`asyncio` for how to use with :class:`can.Notifier`.
Can also be used as an asynchronous iterator::
async for msg in reader:
print(msg)
"""
def __init__(self, loop: Optional[asyncio.events.AbstractEventLoop] = None):
# set to "infinite" size
self.buffer: "asyncio.Queue[Message]" = asyncio.Queue(loop=loop)
def on_message_received(self, msg: Message):
"""Append a message to the buffer.
Must only be called inside an event loop!
"""
self.buffer.put_nowait(msg)
async def get_message(self) -> Message:
"""
Retrieve the latest message when awaited for::
msg = await reader.get_message()
:return: The CAN message.
"""
return await self.buffer.get()
def __aiter__(self) -> AsyncIterator[Message]:
return self
def __anext__(self) -> Awaitable[Message]:
return self.buffer.get()