Apollo CyberRT Python API
1. 背景
Cyber 核心代码是由 C++ 开发，同时为了方便开发者，提供了 Python 接口。
2. CyberRT Python 接口实现思路
Cyber Python 接口的实现思路是在 Cyber C++ 实现的基础上，做了一层 Python 的封装，由 Python 来调用 C++ 的实现函数。Cyber Python Wrapper 的实现没有使用 swig 等第三方工具，完全自主实现，以此保证代码的高可维护性和可读性。
3. 主要接口
目前提供的主要接口包括：
- channel 读、写
- server/client 通信
- record 信息查询
- record 文件读、写
- Time/Duration/Rate 时间操作
- Timer
3.1 Channel 读写接口
使用步骤是：
- 首先创建 Node;
- 创建对应的 reader 或 writer；
- 如果是向 channel 写数据，调用 writer 的 write 接口；
- 如果是从 channel 读数据，调用 node 的 spin，对收到的消息进行消费；
接口定义如下：
class Node:
"""
Class for cyber Node wrapper.
"""
def create_writer(self, name, data_type, qos_depth=1):
"""
create a topic writer for send message to topic.
@param self
@param name str: topic name
@param data_type proto: message class for serialization
"""
def create_reader(self, name, data_type, callback, args=None):
"""
create a topic reader for receive message from topic.
@param self
@param name str: topic name
@param data_type proto: message class for serialization
@callback fn: function to call (fn(data)) when data is
received. If args is set, the function must
accept the args as a second argument,
i.e. fn(data, args)
@args any: additional arguments to pass to the callback
"""
def create_client(self, name, request_data_type, response_data_type):
"""
"""
def create_service(self, name, req_data_type, res_data_type, callback, args=None):
def spin(self):
"""
spin in wait and process message.
@param self
"""
class Writer(object):
"""
Class for cyber writer wrapper.
"""
def write(self, data):
"""
writer msg string
"""
3.2 Record 接口
Record 读的操作是：
- 创建一个 RecordReader;
- 对 Record 进行迭代读；
Record 写的操作是：
- 创建一个 RecordWriter
- 对 Record 进行写消息；
接口定义如下：
class RecordReader(object):
"""
Class for cyber RecordReader wrapper.
"""
def read_messages(self, start_time=0, end_time=18446744073709551615):
"""
read message from bag file.
@param self
@param start_time:
@param end_time:
@return: generator of (message, data_type, timestamp)
"""
def get_messagenumber(self, channel_name):
"""
return message count.
"""
def get_messagetype(self, channel_name):
"""
return message type.
"""
def get_protodesc(self, channel_name):
"""
return message protodesc.
"""
def get_headerstring(self):
"""
return message header string.
"""
def reset(self):
"""
return reset.
"""
return _CYBER_RECORD.PyRecordReader_Reset(self.record_reader)
def get_channellist(self):
"""
return channel list.
"""
return _CYBER_RECORD.PyRecordReader_GetChannelList(self.record_reader)
class RecordWriter(object):
"""
Class for cyber RecordWriter wrapper.
"""
def open(self, path):
"""
open record file for write.
"""
def write_channel(self, channel_name, type_name, proto_desc):
"""
writer channel by channelname,typename,protodesc
"""
def write_message(self, channel_name, data, time, raw = True):
"""
writer msg:channelname,data,time,is data raw
"""
def set_size_fileseg(self, size_kilobytes):
"""
return filesegment size.
"""
def set_intervaltime_fileseg(self, time_sec):
"""
return file interval time.
"""
def get_messagenumber(self, channel_name):
"""
return message count.
"""
def get_messagetype(self, channel_name):
"""
return message type.
"""
def get_protodesc(self, channel_name):
"""
return message protodesc.
"""
3.3 Time 接口
class Timer(object):
def set_option(self, period, callback, oneshot=0):
'''
period The period of the timer, unit is ms
callback The tasks that the timer needs to perform
oneshot 1: perform the callback only after the first timing cycle
0:perform the callback every timed period
'''
def start(self):
def stop(self):
4. 例子
4.1 读 channel （参见 https://github.com/ApolloAuto/apollo/tree/master/cyber/python/cyber_py3/examples/listener.py)
"""Module for example of listener."""
from cyber_py3 import cyber
from cyber.proto.unit_test_pb2 import ChatterBenchmark
def callback(data):
"""
Reader message callback.
"""
print("=" * 80)
print("py:reader callback msg->:")
print(data)
print("=" * 80)
def test_listener_class():
"""
Reader message.
"""
print("=" * 120)
test_node = cyber.Node("listener")
test_node.create_reader("channel/chatter", ChatterBenchmark, callback)
test_node.spin()
if __name__ == '__main__':
cyber.init()
test_listener_class()
cyber.shutdown()
4.2 写 channel（参见https://github.com/ApolloAuto/apollo/tree/master/cyber/python/cyber_py3/examples/talker.py)
"""Module for example of talker."""
import time
from cyber_py3 import cyber
from cyber.proto.unit_test_pb2 import ChatterBenchmark
def test_talker_class():
"""
Test talker.
"""
msg = ChatterBenchmark()
msg.content = "py:talker:send Alex!"
msg.stamp = 9999
msg.seq = 0
print(msg)
test_node = cyber.Node("node_name1")
g_count = 1
writer = test_node.create_writer("channel/chatter", ChatterBenchmark, 6)
while not cyber.is_shutdown():
time.sleep(1)
g_count = g_count + 1
msg.seq = g_count
msg.content = "I am python talker."
print("=" * 80)
print("write msg -> %s" % msg)
writer.write(msg)
if __name__ == '__main__':
cyber.init("talker_sample")
test_talker_class()
cyber.shutdown()
4.3 读写消息到 Record 文件（参见https://github.com/ApolloAuto/apollo/tree/master/cyber/python/cyber_py3/examples/record.py)
cyber/python/cyber_py3/examples/record.py)
```python
"""
Module for example of record.
Run with:
bazel run //cyber/python/cyber_py3/examples:record
"""
import time
from google.protobuf.descriptor_pb2 import FileDescriptorProto
from cyber.proto.unit_test_pb2 import Chatter
from cyber.python.cyber_py3 import record
from modules.common.util.testdata.simple_pb2 import SimpleMessage
MSG_TYPE = "apollo.common.util.test.SimpleMessage"
MSG_TYPE_CHATTER = "apollo.cyber.proto.Chatter"
def test_record_writer(writer_path):
"""
Record writer.
"""
fwriter = record.RecordWriter()
fwriter.set_size_fileseg(0)
fwriter.set_intervaltime_fileseg(0)
if not fwriter.open(writer_path):
print('Failed to open record writer!')
return
print('+++ Begin to writer +++')
# Writer 2 SimpleMessage
msg = SimpleMessage()
msg.text = "AAAAAA"
file_desc = msg.DESCRIPTOR.file
proto = FileDescriptorProto()
file_desc.CopyToProto(proto)
proto.name = file_desc.name
desc_str = proto.SerializeToString()
print(msg.DESCRIPTOR.full_name)
fwriter.write_channel(
'simplemsg_channel', msg.DESCRIPTOR.full_name, desc_str)
fwriter.write_message('simplemsg_channel', msg, 990, False)
fwriter.write_message('simplemsg_channel', msg.SerializeToString(), 991)
# Writer 2 Chatter
msg = Chatter()
msg.timestamp = 99999
msg.lidar_timestamp = 100
msg.seq = 1
file_desc = msg.DESCRIPTOR.file
proto = FileDescriptorProto()
file_desc.CopyToProto(proto)
proto.name = file_desc.name
desc_str = proto.SerializeToString()
print(msg.DESCRIPTOR.full_name)
fwriter.write_channel('chatter_a', msg.DESCRIPTOR.full_name, desc_str)
fwriter.write_message('chatter_a', msg, 992, False)
msg.seq = 2
fwriter.write_message("chatter_a", msg.SerializeToString(), 993)
fwriter.close()
def test_record_reader(reader_path):
"""
Record reader.
"""
freader = record.RecordReader(reader_path)
time.sleep(1)
print('+' * 80)
print('+++ Begin to read +++')
count = 0
for channel_name, msg, datatype, timestamp in freader.read_messages():
count += 1
print('=' * 80)
print('read [%d] messages' % count)
print('channel_name -> %s' % channel_name)
print('msgtime -> %d' % timestamp)
print('msgnum -> %d' % freader.get_messagenumber(channel_name))
print('msgtype -> %s' % datatype)
print('message is -> %s' % msg)
print('***After parse(if needed),the message is ->')
if datatype == MSG_TYPE:
msg_new = SimpleMessage()
msg_new.ParseFromString(msg)
print(msg_new)
elif datatype == MSG_TYPE_CHATTER:
msg_new = Chatter()
msg_new.ParseFromString(msg)
print(msg_new)
if __name__ == '__main__':
test_record_file = "/tmp/test_writer.record"
print('Begin to write record file: {}'.format(test_record_file))
test_record_writer(test_record_file)
print('Begin to read record file: {}'.format(test_record_file))
test_record_reader(test_record_file)