rate_publishers.py

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# twist_mux: rate_publishers.py
#
# Copyright (c) 2014 PAL Robotics SL.
# All Rights Reserved
#
# Permission to use, copy, modify, and/or distribute this software for
# any purpose with or without fee is hereby granted, provided that the
# above copyright notice and this permission notice appear in all
# copies.
# 
# THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
# REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY
# SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
#
# Authors:
#   * Siegfried-A. Gevatter
 
import sys
try:
    import _thread as thread  # Python3
except:
    import thread             # Python2
 
import rospy
 
class _RatePublisher(object):
 
    # How many seconds before the expected time a message may
    # be published.
    _tolerance = 0.01
 
    def __init__(self, topic, msg_type, latch=False):
        self._topic = topic
        self._publisher = rospy.Publisher(topic, msg_type, latch=True)
        self._message = None
        self._period = None  # 1 / freq
        self._last_pub = 0
 
    def pub(self, message, rate=None):
        self._message = message
        self._period = (1. / rate) if rate else None
        self.publish_once()
 
    def stop(self):
        self._period = None
 
    def publish_once(self):
        msg = self._message() if callable(self._message) else self._message
        self._publisher.publish(msg)
        self._last_pub = rospy.Time.now()
 
    def spin_once(self):
        """
        Gives _RatePublisher a chance to publish a stored message.
 
        This method returns the remaining time until the next scheduled
        publication (or -1).
        """
        if not self._period:
            return -1
        elapsed = (rospy.Time.now() - self._last_pub).to_sec()
        if elapsed >= (self._period - self._tolerance):
            self.publish_once()
            return self._period
        return self._period - elapsed
 
 
class RatePublishers(object):
    """
    A class for managing several ROS publishers repeating messages
    with different rates.
 
    The main purpose of this class is for unit testing.
    """
 
    def __init__(self):
        self._publishers = {}
 
    def add_topic(self, topic, msg_type):
        """
        Adds a topic for future publication.
 
        This creates a rospy.Publisher internally. Note that the
        publisher will latch the topic; if that wasn't the case,
        clients might need to sleep before publishing something
        for the first time to give subscribers enough time to
        connect.
        """
        assert topic not in self._publishers
        rate_publisher = _RatePublisher(topic, msg_type, latch=True)
        self._publishers[topic] = rate_publisher
        return rate_publisher
 
    def pub(self, topic, message, rate=None):
        """
        Publishes `message' on the given topic.
 
        If `rate' is not None, the message will be repeated at the
        given rate (expected to be in Hz) until pub() or stop()
        are invoked again.
 
        Note that `rate' may also be a function, in which case
        it'll be invoked for each publication to obtain the message.
        """
        self._publishers[topic].pub(message, rate)
 
    def stop(self, topic):
        """
        Stops repeating any message on the given topic.
        """
        self._publishers[topic].stop()
 
    def spin_once(self):
        """
        Publishes any scheduled messages and returns the amount of
        time until it should be called again.
        """
        # TODO: Create a class that spawns a global thread and provides
        #       createTimer and createWallTimer, just like NodeHandle
        #       does in rospy?
        try:
            next_timeout = sys.maxsize  # Python3
        except AttributeError:
            next_timeout = sys.maxint   # Python2
        for topic in self._publishers.values():
            next_timeout = min(topic.spin_once(), next_timeout)
        return next_timeout
 
 
# TODO: Make this class more generic (keeping track of timeouts itself)?
class TimeoutManager(object):
 
    def __init__(self):
        self._shutdown = False
        self._members = []
 
    def add(self, m):
        self._members.append(m)
 
    def spin(self):
        while not rospy.core.is_shutdown() and not self._shutdown:
            try:
                for m in self._members:
                    m.spin_once()
                    rospy.sleep(0.01)  # FIXME
            except Exception as e:
                rospy.logfatal(e)
 
    def spin_thread(self):
        rospy.loginfo("Spawning thread for TopicTestManager...")
        thread.start_new_thread(self.spin, ())
 
    def shutdown(self):
        self._shutdown = True