diff_subscriber.cpp

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/*
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#include <graph_slam/diff_subscriber.h>
#include <pose_graph/pose_graph_message.h>
#include <pose_graph/GetGraph.h>
#include <boost/thread.hpp>

namespace graph_slam
{

using namespace pose_graph;

DiffSubscriber::DiffSubscriber (const ros::NodeHandle& nh, const DiffSubscriber::DiffCallback& cb) :
  nh_(nh), diff_callback_(cb),
  graph_client_(nh_.serviceClient<GetGraph>("get_graph")), last_id_(0)
{
  // We don't want to wait till the first diff is sent.  So we invoke our own callback
  // with a fake diff to trigger a service call.  Note that it's fine if 
  
  PoseGraphDiff fake_diff;
  fake_diff.id = 42; // Anything but 1
  diffCB(fake_diff);
  
  // Now that the current graph is received, subscribe to the true diff topic
  diff_sub_ = nh_.subscribe("graph_diffs", 10, &DiffSubscriber::diffCB, this);
}


void DiffSubscriber::diffCB (const PoseGraphDiff& diff)
{
  boost::mutex::scoped_lock l(mutex_);
  boost::optional<const PoseGraphDiff&> possible_diff;
  if (diff.id == last_id_+1) {
    applyDiff(&graph_, diff);
    possible_diff = diff;
    last_id_ = diff.id;
  }
  else {
    ROS_INFO_STREAM ("Received diff with id " << diff.id << " while last id is " << last_id_);
    GetGraph srv;
    graph_client_.call(srv);
    graph_ = poseGraphFromRos(srv.response.graph);
    last_id_ = srv.response.id;
    ROS_INFO_STREAM ("New graph has id " << last_id_);
  }
  diff_callback_(possible_diff, graph_);
}

PoseGraph DiffSubscriber::getCurrentGraph () const
{
  boost::mutex::scoped_lock l(mutex_);
  return graph_;
}




} // namespace