Always take std::function<> by value. (#188)

Taking it by reference increases the chance of dangling references
without a significant performance gain.

cartographer/io/pcd_writing_points_processor.cc

@@ -79,7 +79,7 @@ void WriteBinaryPcdPointColor(const Color& color,
 
 std::unique_ptr<PcdWritingPointsProcessor>
 PcdWritingPointsProcessor::FromDictionary(
-    const FileWriterFactory& file_writer_factory,
+    FileWriterFactory file_writer_factory,
     common::LuaParameterDictionary* const dictionary,
     PointsProcessor* const next) {
   return common::make_unique<PcdWritingPointsProcessor>(

cartographer/io/pcd_writing_points_processor.h

@@ -31,7 +31,7 @@ class PcdWritingPointsProcessor : public PointsProcessor {
                             PointsProcessor* next);
 
   static std::unique_ptr<PcdWritingPointsProcessor> FromDictionary(
-      const FileWriterFactory& file_writer_factory,
+      FileWriterFactory file_writer_factory,
       common::LuaParameterDictionary* dictionary, PointsProcessor* next);
 
   ~PcdWritingPointsProcessor() override {}

cartographer/io/ply_writing_points_processor.cc

@@ -70,7 +70,7 @@ void WriteBinaryPlyPointColor(const Color& color,
 
 std::unique_ptr<PlyWritingPointsProcessor>
 PlyWritingPointsProcessor::FromDictionary(
-    const FileWriterFactory& file_writer_factory,
+    FileWriterFactory file_writer_factory,
     common::LuaParameterDictionary* const dictionary,
     PointsProcessor* const next) {
   return common::make_unique<PlyWritingPointsProcessor>(

cartographer/io/ply_writing_points_processor.h

@@ -29,7 +29,7 @@ class PlyWritingPointsProcessor : public PointsProcessor {
                             PointsProcessor* next);
 
   static std::unique_ptr<PlyWritingPointsProcessor> FromDictionary(
-      const FileWriterFactory& file_writer_factory,
+      FileWriterFactory file_writer_factory,
       common::LuaParameterDictionary* dictionary, PointsProcessor* next);
 
   ~PlyWritingPointsProcessor() override {}

cartographer/io/points_processor_pipeline_builder.cc

@@ -46,11 +46,11 @@ void RegisterPlainPointsProcessor(
 
 template <typename PointsProcessorType>
 void RegisterFileWritingPointsProcessor(
-    const FileWriterFactory& file_writer_factory,
+    FileWriterFactory file_writer_factory,
     PointsProcessorPipelineBuilder* const builder) {
   builder->Register(
       PointsProcessorType::kConfigurationFileActionName,
-      [&file_writer_factory](
+      [file_writer_factory](
           common::LuaParameterDictionary* const dictionary,
           PointsProcessor* const next) -> std::unique_ptr<PointsProcessor> {
         return PointsProcessorType::FromDictionary(file_writer_factory,
@@ -60,7 +60,7 @@ void RegisterFileWritingPointsProcessor(
 
 void RegisterBuiltInPointsProcessors(
     const mapping::proto::Trajectory& trajectory,
-    const FileWriterFactory& file_writer_factory,
+    FileWriterFactory file_writer_factory,
     PointsProcessorPipelineBuilder* builder) {
   RegisterPlainPointsProcessor<CountingPointsProcessor>(builder);
   RegisterPlainPointsProcessor<FixedRatioSamplingPointsProcessor>(builder);
@@ -79,7 +79,7 @@ void RegisterBuiltInPointsProcessors(
   // different building levels we walked on to separate the images.
   builder->Register(
       XRayPointsProcessor::kConfigurationFileActionName,
-      [&trajectory, &file_writer_factory](
+      [&trajectory, file_writer_factory](
           common::LuaParameterDictionary* const dictionary,
           PointsProcessor* const next) -> std::unique_ptr<PointsProcessor> {
         return XRayPointsProcessor::FromDictionary(

cartographer/io/points_processor_pipeline_builder.h

@@ -62,7 +62,7 @@ class PointsProcessorPipelineBuilder {
 // 'builder'.
 void RegisterBuiltInPointsProcessors(
     const mapping::proto::Trajectory& trajectory,
-    const FileWriterFactory& file_writer_factory,
+    FileWriterFactory file_writer_factory,
     PointsProcessorPipelineBuilder* builder);
 
 }  // namespace io

cartographer/io/xray_points_processor.cc

@@ -136,7 +136,7 @@ bool ContainedIn(
 XRayPointsProcessor::XRayPointsProcessor(
     const double voxel_size, const transform::Rigid3f& transform,
     const std::vector<mapping::Floor>& floors, const string& output_filename,
-    const FileWriterFactory& file_writer_factory, PointsProcessor* const next)
+    FileWriterFactory file_writer_factory, PointsProcessor* const next)
     : next_(next),
       file_writer_factory_(file_writer_factory),
       floors_(floors),
@@ -151,7 +151,7 @@ XRayPointsProcessor::XRayPointsProcessor(
 
 std::unique_ptr<XRayPointsProcessor> XRayPointsProcessor::FromDictionary(
     const mapping::proto::Trajectory& trajectory,
-    const FileWriterFactory& file_writer_factory,
+    FileWriterFactory file_writer_factory,
     common::LuaParameterDictionary* const dictionary,
     PointsProcessor* const next) {
   std::vector<mapping::Floor> floors;
@@ -200,8 +200,8 @@ void XRayPointsProcessor::WriteVoxels(const Aggregation& aggregation,
     const Eigen::Array3i cell_index = it.GetCellIndex();
     const Eigen::Array2i pixel = voxel_index_to_pixel(cell_index);
     PixelData& pixel_data = image(pixel.y(), pixel.x());
-    const auto& column_data =
-        aggregation.column_data.at(std::make_pair(cell_index[1], cell_index[2]));
+    const auto& column_data = aggregation.column_data.at(
+        std::make_pair(cell_index[1], cell_index[2]));
     pixel_data.mean_r = column_data.sum_r / column_data.count;
     pixel_data.mean_g = column_data.sum_g / column_data.count;
     pixel_data.mean_b = column_data.sum_b / column_data.count;

cartographer/io/xray_points_processor.h

@@ -39,12 +39,12 @@ class XRayPointsProcessor : public PointsProcessor {
   XRayPointsProcessor(double voxel_size, const transform::Rigid3f& transform,
                       const std::vector<mapping::Floor>& floors,
                       const string& output_filename,
-                      const FileWriterFactory& file_writer_factory,
+                      FileWriterFactory file_writer_factory,
                       PointsProcessor* next);
 
   static std::unique_ptr<XRayPointsProcessor> FromDictionary(
       const mapping::proto::Trajectory& trajectory,
-      const FileWriterFactory& file_writer_factory,
+      FileWriterFactory file_writer_factory,
       common::LuaParameterDictionary* dictionary, PointsProcessor* next);
 
   ~XRayPointsProcessor() override {}
@@ -65,12 +65,13 @@ class XRayPointsProcessor : public PointsProcessor {
     std::map<std::pair<int, int>, ColumnData> column_data;
   };
 
-  void WriteVoxels(const Aggregation& aggregation, FileWriter* const file_writer);
+  void WriteVoxels(const Aggregation& aggregation,
+                   FileWriter* const file_writer);
   void Insert(const PointsBatch& batch, const transform::Rigid3f& transform,
               Aggregation* aggregation);
 
   PointsProcessor* const next_;
-  const FileWriterFactory& file_writer_factory_;
+  FileWriterFactory file_writer_factory_;
 
   // If empty, we do not separate into floors.
   std::vector<mapping::Floor> floors_;

cartographer/io/xyz_writing_points_processor.cc

@@ -27,7 +27,7 @@ XyzWriterPointsProcessor::XyzWriterPointsProcessor(
 
 std::unique_ptr<XyzWriterPointsProcessor>
 XyzWriterPointsProcessor::FromDictionary(
-    const FileWriterFactory& file_writer_factory,
+    FileWriterFactory file_writer_factory,
     common::LuaParameterDictionary* const dictionary,
     PointsProcessor* const next) {
   return common::make_unique<XyzWriterPointsProcessor>(

cartographer/io/xyz_writing_points_processor.h

@@ -36,7 +36,7 @@ class XyzWriterPointsProcessor : public PointsProcessor {
   XyzWriterPointsProcessor(std::unique_ptr<FileWriter>, PointsProcessor* next);
 
   static std::unique_ptr<XyzWriterPointsProcessor> FromDictionary(
-      const FileWriterFactory& file_writer_factory,
+      FileWriterFactory file_writer_factory,
       common::LuaParameterDictionary* dictionary, PointsProcessor* next);
 
   ~XyzWriterPointsProcessor() override {}