ros2 topic 源码解析

ros2 命令加载过程
ros2 topic代码位置：ros2\src\ros2cli\ros2topic
最终运作在ros2topic文件中
setup.py 定义挂载点,加载命令的执行函数

from setuptools import find_packages
from setuptools import setup
package_name = 'ros2topic'
setup(name=package_name,version='0.13.1',packages=find_packages(exclude=['test']),data_files=[('share/' + package_name, ['package.xml']),('share/ament_index/resource_index/packages',['resource/' + package_name]),],install_requires=['ros2cli'],zip_safe=True,author='Dirk Thomas',author_email='dthomas@osrfoundation.org',maintainer='Claire Wang, Mabel Zhang',maintainer_email='clairewang@openrobotics.org, mabel@openrobotics.org',url='https://github.com/ros2/ros2cli/tree/master/ros2topic',download_url='https://github.com/ros2/ros2cli/releases',keywords=[],classifiers=['Environment :: Console','Intended Audience :: Developers','License :: OSI Approved :: Apache Software License','Programming Language :: Python',],description='The topic command for ROS 2 command line tools.',long_description="""\
The package provides the topic command for the ROS 2 command line tools.""",license='Apache License, Version 2.0',tests_require=['pytest'],entry_points={'ros2cli.command': ['topic = ros2topic.command.topic:TopicCommand',],'ros2cli.extension_point': ['ros2topic.verb = ros2topic.verb:VerbExtension',],'ros2topic.verb': ['bw = ros2topic.verb.bw:BwVerb','delay = ros2topic.verb.delay:DelayVerb','echo = ros2topic.verb.echo:EchoVerb','find = ros2topic.verb.find:FindVerb','hz = ros2topic.verb.hz:HzVerb','info = ros2topic.verb.info:InfoVerb','list = ros2topic.verb.list:ListVerb','pub = ros2topic.verb.pub:PubVerb','type = ros2topic.verb.type:TypeVerb',],}
)

例如： ros2 topic list .会运行ros2topic.verb.list:ListVerb
先运行下面的main函数

from ros2cli.command import add_subparsers_on_demand
from ros2cli.command import CommandExtensionclass TopicCommand(CommandExtension):"""Various topic related sub-commands."""def add_arguments(self, parser, cli_name):self._subparser = parserparser.add_argument('--include-hidden-topics', action='store_true',help='Consider hidden topics as well')# add arguments and sub-commands of verbsadd_subparsers_on_demand(parser, cli_name, '_verb', 'ros2topic.verb', required=False)def main(self, *, parser, args):if not hasattr(args, '_verb'):# in case no verb was passedself._subparser.print_help()return 0extension = getattr(args, '_verb')# call the verb's main methodreturn extension.main(args=args)

下面执行 ros2\src\ros2cli\ros2topic\ros2topic\verb\list.py

from ros2cli.node.strategy import add_arguments as add_strategy_node_arguments
from ros2cli.node.strategy import NodeStrategy
from ros2topic.api import get_topic_names_and_types
from ros2topic.verb import VerbExtensionclass ListVerb(VerbExtension):"""Output a list of available topics."""# topic 后面参数解析def add_arguments(self, parser, cli_name):add_strategy_node_arguments(parser)parser.add_argument('-t', '--show-types', action='store_true',help='Additionally show the topic type')parser.add_argument('-c', '--count-topics', action='store_true',help='Only display the number of topics discovered')# duplicate the following argument from the command for visibilityparser.add_argument('--include-hidden-topics', action='store_true',help='Consider hidden topics as well')parser.add_argument('-v', '--verbose', action='store_true',help='List full details about each topic')@staticmethoddef show_topic_info(topic_info, is_publisher):message = ('Published' if is_publisher else 'Subscribed') + ' topics:\n'for (topic_name, topic_types, pub_count, sub_count) in topic_info:count = pub_count if is_publisher else sub_countif count:topic_types_formatted = ', '.join(topic_types)count_str = str(count) + ' ' + ('publisher' if is_publisher else 'subscriber') \+ ('s' if count > 1 else '')message += f' * {topic_name} [{topic_types_formatted}] {count_str}\n'return messagedef main(self, *, args):topic_info = []# NodeStrategy包括两个实现DirectNode和DaemonNode，DaemonNode在localhost 11511+domain 端口上，DirectNode#下面代码走DaemonNode分支 with NodeStrategy(args) as node:topic_names_and_types = get_topic_names_and_types(node=node,include_hidden_topics=args.include_hidden_topics)for (topic_name, topic_types) in topic_names_and_types:if args.verbose:pub_count = node.count_publishers(topic_name)sub_count = node.count_subscribers(topic_name)topic_info.append((topic_name, topic_types, pub_count, sub_count))else:topic_info.append((topic_name, topic_types, 0, 0))#输出发现主题个数， -cif args.count_topics:  print(len(topic_names_and_types))elif topic_names_and_types:# 列出有关每个主题的完整详细信息 -vif args.verbose:print(self.show_topic_info(topic_info, is_publisher=True))print(self.show_topic_info(topic_info, is_publisher=False))else:# ros2 topic list 默认输出for (topic_name, topic_types, _, _) in topic_info:msg = '{topic_name}'topic_types_formatted = ', '.join(topic_types)if args.show_types:msg += ' [{topic_types_formatted}]'print(msg.format_map(locals()))

列如
ros2 topic list -c
ros2 topic list -v
ros2 topic list -t
ros2 topic list --include-hidden-topics

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