text: // Copyright 2020 Open Source Robotics Foundation, Inc.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //     http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  #ifndef RMW__EVENTS_STATUSES__LIVELINESS_CHANGED_H_
  #define RMW__EVENTS_STATUSES__LIVELINESS_CHANGED_H_
  
  #include <stdint.h>
  
  #include "rmw/visibility_control.h"
  
  #ifdef __cplusplus
  extern "C"
  {
  #endif
  
  /// QoS Liveliness Changed information provided by a subscription.
  typedef struct RMW_PUBLIC_TYPE rmw_liveliness_changed_status_t
  {
    /**
     * The total number of currently active Publishers which publish to the topic associated with
     * the Subscription.
     * This count increases when a newly matched Publisher asserts its liveliness for the first time
     * or when a Publisher previously considered to be not alive reasserts its liveliness.
     * The count decreases when a Publisher considered alive fails to assert its liveliness and
     * becomes not alive, whether because it was deleted normally or for some other reason.
     */
    int32_t alive_count;
    /**
     * The total count of current Publishers which publish to the topic associated with the
     * Subscription that are no longer asserting their liveliness.
     * This count increases when a Publisher considered alive fails to assert its liveliness and
     * becomes not alive for some reason other than the normal deletion of that Publisher.
     * It decreases when a previously not alive Publisher either reasserts its liveliness or is
     * deleted normally.
     */
    int32_t not_alive_count;
    /// The change in the alive_count since the status was last read.
    int32_t alive_count_change;
    /// The change in the not_alive_count since the status was last read.
    int32_t not_alive_count_change;
  } rmw_liveliness_changed_status_t;
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif  // RMW__EVENTS_STATUSES__LIVELINESS_CHANGED_H_
  