trajectory_interface.h

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// Copyright (C) 2013, PAL Robotics S.L.
//
// Redistribution and use in source and binary forms, with or without
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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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//   * Neither the name of PAL Robotics S.L. nor the names of its
//     contributors may be used to endorse or promote products derived from
//     this software without specific prior written permission.
//
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#pragma once
 
 
#include <algorithm>
#include <iterator>
#include <vector>
 
// Things to generalize:
// - State specification: What values (pos, vel, acc, ...), and their dimension (4 for quats, 1 for scalars)
// - State might be different for derivatives: Quat == 4, ang vel == 3: Solve doing w=[w0, w1, w2, 0]
// - Sample state vs. sample pos and derivatives separately
// - Manage and find active segments of heretogeneous types
 
// NOTES:
// - Segments in original implementation are an open interval on the start time. We are making them closed
// - If an action goal superceeds another and the new trajectory starts in the future, until that time no constraint
//   enforcement will take place. Odd.
 
namespace trajectory_interface
{
 
namespace internal
{
 
// NOTE: Implement as a lambda expression when C++11 becomes mainstream
template<class Time, class Segment>
inline bool isBeforeSegment(const Time& time, const Segment& segment)
{
  return time < segment.startTime();
}
 
} // namespace
 
template<class TrajectoryIterator, class Time>
inline TrajectoryIterator findSegment(TrajectoryIterator first, TrajectoryIterator last, const Time& time)
{
  typedef typename std::iterator_traits<TrajectoryIterator>::value_type Segment;
  return (first == last || internal::isBeforeSegment(time, *first))
         ? last // Optimization when time preceeds all segments, or when an empty range is passed
         : --std::upper_bound(first, last, time, internal::isBeforeSegment<Time, Segment>); // Notice decrement operator
}
 
template<class Trajectory, class Time>
inline typename Trajectory::const_iterator findSegment(const Trajectory& trajectory, const Time& time)
{
  return findSegment(trajectory.begin(), trajectory.end(), time);
}
 
template<class Trajectory, class Time>
inline typename Trajectory::iterator findSegment(Trajectory& trajectory, const Time& time)
{
  return findSegment(trajectory.begin(), trajectory.end(), time);
}
 
template<class Trajectory>
inline typename Trajectory::const_iterator sample(const Trajectory&                             trajectory,
                                                  const typename Trajectory::value_type::Time&  time,
                                                        typename Trajectory::value_type::State& state)
{
  typename Trajectory::const_iterator it = findSegment(trajectory, time);
  if (it != trajectory.end())
  {
    it->sample(time, state); // Segment found at specified time
  }
  else if (!trajectory.empty())
  {
    trajectory.front().sample(time, state); // Specified time preceeds trajectory start time
  }
  return it;
}
 
} // namespace