Program Listing for File message_traits.h

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/*
 * Copyright (C) 2009, Willow Garage, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
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 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
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 *     contributors may be used to endorse or promote products derived from
 *     this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// File imported from
// https://github.com/ros/roscpp_core/blob/38b9663/roscpp_traits/include/ros/message_traits.h

#ifndef MESSAGE_FILTERS__MESSAGE_TRAITS_H_
#define MESSAGE_FILTERS__MESSAGE_TRAITS_H_

#include <type_traits>

#include <rclcpp/rclcpp.hpp>

namespace message_filters
{
namespace message_traits
{

template<typename M, typename = void> struct HasHeader : public std::false_type {};

template <typename M>
struct HasHeader<M, decltype((void) M::header)> : std::true_type {};

template<typename M, typename Enable = void>
struct FrameId
{
  static std::string* pointer(M& m) { (void)m; return nullptr; }
  static std::string const* pointer(const M& m) { (void)m; return nullptr; }
};
 template<typename M>
struct FrameId<M, typename std::enable_if<HasHeader<M>::value>::type >
{
  static std::string* pointer(M& m) { return &m.header.frame_id; }
  static std::string const* pointer(const M& m) { return &m.header.frame_id; }
  static std::string value(const M& m) { return m.header.frame_id; }
};

template<typename M, typename Enable = void>
struct TimeStamp
{
  static rclcpp::Time value(const M& m) {
    (void)m;
    return rclcpp::Time();
  }
};

template<typename M>
struct TimeStamp<M, typename std::enable_if<HasHeader<M>::value>::type >
{
  static rclcpp::Time value(const M& m) {
    return rclcpp::Time(m.header.stamp, RCL_ROS_TIME);
  }
};

}  // namespace message_traits
}  // namespace message_filters

#endif  // MESSAGE_FILTERS__MESSAGE_TRAITS_H_