cache.cpp

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/*
 * Copyright (c) 2008, Willow Garage, Inc.
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 *       this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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#include "tf/time_cache.h"
#include "tf/exceptions.h"
 
#include "tf/LinearMath/Transform.h"
#include <geometry_msgs/TransformStamped.h>
 
#include "ros/assert.h"
 
using namespace tf;
 
TransformStorage::TransformStorage()
{
}
 
TransformStorage::TransformStorage(const StampedTransform& data, CompactFrameID frame_id,
                                   CompactFrameID child_frame_id)
: rotation_(data.getRotation())
, translation_(data.getOrigin())
, stamp_(data.stamp_)
, frame_id_(frame_id)
, child_frame_id_(child_frame_id)
{ }
 
TimeCache::TimeCache(ros::Duration max_storage_time)
: max_storage_time_(max_storage_time)
{}
 
// hoisting these into separate functions causes an ~8% speedup.  Removing calling them altogether adds another ~10%
void createEmptyException(std::string *error_str)
{
  if (error_str)
  {
    *error_str = "Unable to lookup transform, cache is empty";
  }
}
 
void createExtrapolationException1(ros::Time t0, ros::Time t1, std::string* error_str)
{
  if (error_str)
  {
    std::stringstream ss;
    ss << "Lookup would require extrapolation at time " << t0 << ", but only time " << t1 << " is in the buffer";
    *error_str = ss.str();
  }
}
 
void createExtrapolationException2(ros::Time t0, ros::Time t1, std::string* error_str)
{
  if (error_str)
  {
    std::stringstream ss;
    ss << "Lookup would require extrapolation into the future.  Requested time " << t0 << " but the latest data is at time " << t1;
    *error_str = ss.str();
  }
}
 
void createExtrapolationException3(ros::Time t0, ros::Time t1, std::string* error_str)
{
  if (error_str)
  {
    std::stringstream ss;
    ss << "Lookup would require extrapolation into the past.  Requested time " << t0 << " but the earliest data is at time " << t1;
    *error_str = ss.str();
  }
}
 
uint8_t TimeCache::findClosest(const TransformStorage*& one, const TransformStorage*& two, ros::Time target_time, std::string* error_str)
{
  //No values stored
  if (storage_.empty())
  {
    createEmptyException(error_str);
    return 0;
  }
 
  //If time == 0 return the latest
  if (target_time.isZero())
  {
    one = &(*storage_.rbegin());
    return 1;
  }
 
  // One value stored
  if (++storage_.begin() == storage_.end())
  {
    const TransformStorage& ts = *storage_.begin();
    if (ts.stamp_ == target_time)
    {
      one = &ts;
      return 1;
    }
    else
    {
      createExtrapolationException1(target_time, ts.stamp_, error_str);
      return 0;
    }
  }
 
  ros::Time latest_time = (*storage_.rbegin()).stamp_;
  ros::Time earliest_time = (*(storage_.begin())).stamp_;
 
  if (target_time == latest_time)
  {
    one = &(*storage_.rbegin());
    return 1;
  }
  else if (target_time == earliest_time)
  {
    one = &(*storage_.begin());
    return 1;
  }
  // Catch cases that would require extrapolation
  else if (target_time > latest_time)
  {
    createExtrapolationException2(target_time, latest_time, error_str);
    return 0;
  }
  else if (target_time < earliest_time)
  {
    createExtrapolationException3(target_time, earliest_time, error_str);
    return 0;
  }
 
  //Create a temporary object to compare to when searching the lower bound via std::set
  TransformStorage tmp;
  tmp.stamp_ = target_time;
 
  //Find the first value equal or higher than the target value
  L_TransformStorage::iterator storage_it = storage_.upper_bound(tmp);
 
  //Finally the case were somewhere in the middle  Guarenteed no extrapolation :-)
  two = &*(storage_it); //Newer
  one = &*(--storage_it); //Older
 
  return 2;
 
}
 
void TimeCache::interpolate(const TransformStorage& one, const TransformStorage& two, ros::Time time, TransformStorage& output)
{
  // Check for zero distance case
  if( two.stamp_ == one.stamp_ )
  {
    output = two;
    return;
  }
  //Calculate the ratio
  tfScalar ratio = (time.toSec() - one.stamp_.toSec()) / (two.stamp_.toSec() - one.stamp_.toSec());
 
  //Interpolate translation
  output.translation_.setInterpolate3(one.translation_, two.translation_, ratio);
 
  //Interpolate rotation
  output.rotation_ = slerp( one.rotation_, two.rotation_, ratio);
 
  output.stamp_ = one.stamp_;
  output.frame_id_ = one.frame_id_;
  output.child_frame_id_ = one.child_frame_id_;
}
 
bool TimeCache::getData(ros::Time time, TransformStorage & data_out, std::string* error_str) //returns false if data not available
{
  const TransformStorage* p_temp_1 = NULL;
  const TransformStorage* p_temp_2 = NULL;
 
  int num_nodes = findClosest(p_temp_1, p_temp_2, time, error_str);
  if (num_nodes == 0)
  {
    return false;
  }
  else if (num_nodes == 1)
  {
    data_out = *p_temp_1;
  }
  else if (num_nodes == 2)
  {
    if( p_temp_1->frame_id_ == p_temp_2->frame_id_)
    {
      interpolate(*p_temp_1, *p_temp_2, time, data_out);
    }
    else
    {
      data_out = *p_temp_1;
    }
  }
  else
  {
    ROS_BREAK();
  }
 
  return true;
}
 
CompactFrameID TimeCache::getParent(ros::Time time, std::string* error_str)
{
  const TransformStorage* p_temp_1 = NULL;
  const TransformStorage* p_temp_2 = NULL;
 
  int num_nodes = findClosest(p_temp_1, p_temp_2, time, error_str);
  if (num_nodes == 0)
  {
    return 0;
  }
 
  return p_temp_1->frame_id_;
}
 
bool TimeCache::insertData(const TransformStorage& new_data)
{
 
  if (storage_.begin() != storage_.end())
  {
      // trying to add data that dates back longer than we want to keep history
      if (storage_.rbegin()->stamp_ > new_data.stamp_ + max_storage_time_)
        return false;
 
      // if we already have data at that exact time, delete it to ensure the latest data is stored
      if (storage_.rbegin()->stamp_ >= new_data.stamp_)
      {
         L_TransformStorage::iterator storage_it  = storage_.find(new_data);
         if (storage_it != storage_.end())
                storage_.erase(storage_it);
      }
  }
 
  storage_.insert(storage_.end(), new_data);
 
  pruneList();
 
  return true;
}
 
void TimeCache::clearList()
{
  storage_.clear();
}
 
unsigned int TimeCache::getListLength()
{
  return storage_.size();
}
 
P_TimeAndFrameID TimeCache::getLatestTimeAndParent()
{
  if (storage_.empty())
  {
    return std::make_pair(ros::Time(), 0);
  }
 
  const TransformStorage& ts = *storage_.rbegin();
  return std::make_pair(ts.stamp_, ts.frame_id_);
}
 
ros::Time TimeCache::getLatestTimestamp()
{
  if (storage_.empty()) return ros::Time(); //empty list case
  return storage_.rbegin()->stamp_;
}
 
ros::Time TimeCache::getOldestTimestamp()
{
  if (storage_.empty()) return ros::Time(); //empty list case
  return storage_.begin()->stamp_;
}
 
void TimeCache::pruneList()
{
  ros::Time latest_time = storage_.rbegin()->stamp_;
 
  while(!storage_.empty() && storage_.begin()->stamp_ + max_storage_time_ < latest_time)
  {
    storage_.erase(storage_.begin());
  }
 
}