use duration to compute the delay

yechun1 · yechun1 · commit 34e400a0b022 · 2018-09-12T10:01:03.000+08:00
Signed-off-by: Chris Ye &lt;chris.ye@intel.com&gt;
diff --git a/ros2topic/ros2topic/verb/delay.py b/ros2topic/ros2topic/verb/delay.py
@@ -42,6 +42,7 @@
 
 from rclpy.expand_topic_name import expand_topic_name
 from rclpy.qos import qos_profile_sensor_data
+from rclpy.time import Time
 from rclpy.validate_full_topic_name import validate_full_topic_name
 from ros2cli.node.direct import DirectNode
 from ros2topic.api import get_topic_names_and_types
@@ -114,12 +115,9 @@ def callback_delay(self, msg):
                 self.msg_tn = curr
                 self.delays = []
             else:
-                curr_sec = curr_rostime.to_msg().sec
-                curr_nanosec = curr_rostime.to_msg().nanosec
-
-                delay = ((curr_sec + curr_nanosec * 1e-9) -
-                         (msg.header.stamp.sec + msg.header.stamp.nanosec * 1e-9))
-                self.delays.append(delay)
+                # store the duration nanoseconds in self.delays
+                duration = (curr_rostime - Time.from_msg(msg.header.stamp))
+                self.delays.append(duration.nanoseconds)
                 self.msg_tn = curr
 
             if len(self.delays) > self.window_size:
@@ -158,8 +156,9 @@ def print_delay(self):
             print('no new messages')
             return
         delay, min_delta, max_delta, std_dev, window = ret
+        # convert nanoseconds to seconds when print
         print('average delay: %.3f\n\tmin: %.3fs max: %.3fs std dev: %.5fs window: %s'
-              % (delay, min_delta, max_delta, std_dev, window))
+              % (delay * 1e-9, min_delta * 1e-9, max_delta * 1e-9, std_dev * 1e-9, window))
 
 
 def _rostopic_delay(node, topic, window_size=-1):
