Function DecodeTriangles

libs/coding/geometry_coding.cpp:453–517

}

void DecodeTriangles(coding::InDeltasT const & deltas, m2::PointU const & basePoint, m2::PointU const & maxPoint,
                     coding::OutPointsT & points)
{
  size_t const count = deltas.size();
  ASSERT_GREATER(count, 2, ());

  m2::PointD const maxPointD(maxPoint);

  points.push_back(coding::DecodePointDeltaFromUint(deltas[0], basePoint));
  points.push_back(coding::DecodePointDeltaFromUint(deltas[1], points.back()));
  points.push_back(coding::DecodePointDeltaFromUint(deltas[2] >> 2, points.back()));

  std::stack<size_t> st;

  size_t ind = 2;
  uint8_t treeBits = deltas[2] & 3;

  for (size_t i = 3; i < count;)
  {
    // points 0, 1 - is a common edge
    // point 2 - is an opposite point for new triangle to calculate prediction
    size_t trg[3];

    if (treeBits & 1)
    {
      // common edge is 1->2
      trg[0] = ind;
      trg[1] = ind - 1;
      trg[2] = ind - 2;

      // push to stack for further processing
      if (treeBits & 2)
        st.push(ind);
    }
    else if (treeBits & 2)
    {
      // common edge is 2->0
      trg[0] = ind - 2;
      trg[1] = ind;
      trg[2] = ind - 1;
    }
    else
    {
      // end of chain - pop current from stack
      ASSERT(!st.empty(), ());
      ind = st.top();
      st.pop();
      treeBits = 2;
      continue;
    }

    // push points
    points.push_back(points[trg[0]]);
    points.push_back(points[trg[1]]);
    points.push_back(coding::DecodePointDeltaFromUint(
        deltas[i] >> 2, coding::PredictPointInTriangle(maxPointD, points[trg[0]], points[trg[1]], points[trg[2]])));

    // next step