text: // ----------------------------------------------------------------------------
  // -                        Open3D: www.open3d.org                            -
  // ----------------------------------------------------------------------------
  // The MIT License (MIT)
  //
  // Copyright (c) 2018-2021 www.open3d.org
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  // IN THE SOFTWARE.
  // ----------------------------------------------------------------------------
  
  #include <cstdio>
  
  #include "open3d/core/Dtype.h"
  #include "open3d/core/Tensor.h"
  #include "open3d/io/FileFormatIO.h"
  #include "open3d/t/io/PointCloudIO.h"
  #include "open3d/utility/FileSystem.h"
  #include "open3d/utility/Logging.h"
  #include "open3d/utility/ProgressReporters.h"
  
  namespace open3d {
  namespace t {
  namespace io {
  
  open3d::io::FileGeometry ReadFileGeometryTypeXYZI(const std::string &path) {
      return open3d::io::CONTAINS_POINTS;
  }
  
  bool ReadPointCloudFromXYZI(const std::string &filename,
                              geometry::PointCloud &pointcloud,
                              const open3d::io::ReadPointCloudOption &params) {
      try {
          utility::filesystem::CFile file;
          if (!file.Open(filename, "r")) {
              utility::LogWarning("Read XYZI failed: unable to open file: {}",
                                  filename);
              return false;
          }
          utility::CountingProgressReporter reporter(params.update_progress);
          reporter.SetTotal(file.GetFileSize());
          int64_t num_points = file.GetNumLines();
  
          pointcloud.Clear();
          core::Tensor points({num_points, 3}, core::Dtype::Float64);
          core::Tensor intensities({num_points, 1}, core::Dtype::Float64);
          double *points_ptr = points.GetDataPtr<double>();
          double *intensities_ptr = intensities.GetDataPtr<double>();
  
          int i = 0;
          double x, y, z, I;
          const char *line_buffer;
          while ((line_buffer = file.ReadLine())) {
              if (sscanf(line_buffer, "%lf %lf %lf %lf", &x, &y, &z, &I) == 4) {
                  points_ptr[3 * i + 0] = x;
                  points_ptr[3 * i + 1] = y;
                  points_ptr[3 * i + 2] = z;
                  intensities_ptr[i] = I;
              }
              if (++i % 1000 == 0) {
                  reporter.Update(file.CurPos());
              }
          }
          pointcloud.SetPoints(points);
          pointcloud.SetPointAttr("intensities", intensities);
          reporter.Finish();
  
          return true;
      } catch (const std::exception &e) {
          utility::LogWarning("Read XYZ failed with exception: {}", e.what());
          return false;
      }
  }
  
  bool WritePointCloudToXYZI(const std::string &filename,
                             const geometry::PointCloud &pointcloud,
                             const open3d::io::WritePointCloudOption &params) {
      if (!pointcloud.HasPointAttr("intensities")) {
          return false;
      }
  
      try {
          utility::filesystem::CFile file;
          if (!file.Open(filename, "w")) {
              utility::LogWarning("Write XYZI failed: unable to open file: {}",
                                  filename);
              return false;
          }
          utility::CountingProgressReporter reporter(params.update_progress);
          const core::Tensor &points = pointcloud.GetPoints();
          if (!points.GetShape().IsCompatible({utility::nullopt, 3})) {
              utility::LogWarning(
                      "Write XYZI failed: Shape of points is {}, but it should "
                      "be Nx3.",
                      points.GetShape());
              return false;
          }
          const core::Tensor &intensities =
                  pointcloud.GetPointAttr("intensities");
          if (points.GetShape(0) != intensities.GetShape(0)) {
              utility::LogWarning(
                      "Write XYZI failed: Points ({}) and intensities ({}) have "
                      "different lengths.",
                      points.GetShape(0), intensities.GetShape(0));
              return false;
          }
          reporter.SetTotal(points.GetShape(0));
  
          for (int i = 0; i < points.GetShape(0); i++) {
              if (fprintf(file.GetFILE(), "%.10f %.10f %.10f %.10f\n",
                          points[i][0].Item<double>(),
                          points[i][1].Item<double>(),
                          points[i][2].Item<double>(),
                          intensities[i][0].Item<double>()) < 0) {
                  utility::LogWarning(
                          "Write XYZI failed: unable to write file: {}",
                          filename);
                  return false;  // error happened during writing.
              }
              if (i % 1000 == 0) {
                  reporter.Update(i);
              }
          }
          reporter.Finish();
          return true;
      } catch (const std::exception &e) {
          utility::LogWarning("Write XYZI failed with exception: {}", e.what());
          return false;
      }
  }
  
  }  // namespace io
  }  // namespace t
  }  // namespace open3d
  