add @brief and explain comments

nebula_decoders/include/nebula_decoders/nebula_decoders_velodyne/decoders/velodyne_generic_decoder.hpp

@@ -104,7 +104,7 @@ class VelodyneDecoder : public VelodyneScanDecoder
   }
 
   int pointsPerPacket() { return BLOCKS_PER_PACKET * CHANNELS_PER_BLOCK; }
-
+  
   void reset_pointcloud(size_t n_pts, double time_stamp)
   {
     //  scan_pc_.reset(new NebulaPointCloud);
@@ -286,7 +286,7 @@ class VelodyneDecoder : public VelodyneScanDecoder
                 sensor_.getAzimuthCorrected(azimuth, azimuth_diff, firing_seq, firing_order);
 
               // Condition added to avoid calculating points which are not in the interesting
-              // defined area (cloud_min_angle < area < cloud_max_angle).
+              // defined area (cloud_min_angle <= area <= cloud_max_angle).
               if (true) {
                 // convert polar coordinates to Euclidean XYZ.
                 const float cos_vert_angle = corrections.cos_vert_correction;

nebula_decoders/include/nebula_decoders/nebula_decoders_velodyne/decoders/velodyne_sensor.hpp

@@ -10,10 +10,16 @@ namespace drivers
 class VelodyneSensor
 {
 public:
+  // To ignore an empty data blocks which is created by only VLS128 dual return mode case
+  /// @brief eash VLP lidars packat structure in user manual. If you know details, see commens in each <vlp_list>.hpp file.
   virtual int getNumPaddingBlocks(bool /* dual_return */) { return 0; }
 
+  // calculate and stack the firing timing for each laser timeing used in getAzimuthCorrected to calculate the corrected azimuth
+  /// @brief each VLP lidar laser timing in user manual. If you know details, see commens in each <vlp_list>.hpp file.
   virtual bool fillAzimuthCache() { return false; }
 
+  // calculate the corrected azimuth from each firing timing.
+  /// @brief each VLP calculating code sample in user manual. If you know details, see commens in each <vlp_list>.hpp file.
   virtual uint16_t getAzimuthCorrected(
     uint16_t azimuth, float azimuth_diff, int firing_sequence, int firing_order) = 0;
 };

nebula_decoders/include/nebula_decoders/nebula_decoders_velodyne/decoders/vlp_16.hpp

@@ -9,6 +9,12 @@ namespace drivers
 class VLP16 : public VelodyneSensor
 {
 public:
+  /// @brief fomula from VLP16 User manual in p.64
+  /// @param azimuth Azimuth angle
+  /// @param azimuth_diff Azimuth difference
+  /// @param firing_sequence Firing sequence
+  /// @param firing_order Firing order
+  /// @return Corrected azimuth
   uint16_t getAzimuthCorrected(
     uint16_t azimuth, float azimuth_diff, int firing_sequence, int firing_order)
   {
@@ -20,6 +26,7 @@ class VLP16 : public VelodyneSensor
     return static_cast<uint16_t>(round(azimuth_corrected)) % 36000;
   }
 
+  // Choose the correct azimuth from the 2 azimuthes
   uint16_t getTrueRotation(uint16_t azimuth_corrected, uint16_t current_block_rotation)
   {
     return azimuth_corrected;

nebula_decoders/include/nebula_decoders/nebula_decoders_velodyne/decoders/vlp_32.hpp

@@ -9,6 +9,8 @@ namespace drivers
 class VLP32 : public VelodyneSensor
 {
 public:
+// calculate and stack the firing timing for each laser timeing
+/// @brief laser timing for VLP32 from VLP32 User manual in p.61
   bool fillAzimuthCache()
   {
     for (uint8_t i = 0; i < 16; i++) {
@@ -17,6 +19,11 @@ class VLP32 : public VelodyneSensor
     return true;
   }
 
+  /// @brief fomula from VLP32 User manual in p.62
+  /// @param azimuth Azimuth angle
+  /// @param azimuth_diff Azimuth difference between a current azimuth and a next azimuth
+  /// @param firing_order Firing order
+  /// @return Corrected azimuth
   uint16_t getAzimuthCorrected(
     uint16_t azimuth, float azimuth_diff, int /* firing_sequence */, int firing_order)
   {
@@ -25,6 +32,7 @@ class VLP32 : public VelodyneSensor
     return static_cast<uint16_t>(round(azimuth_corrected)) % 36000;
   }
 
+  // Choose the correct azimuth from the 2 azimuthes
   uint16_t getTrueRotation(uint16_t azimuth_corrected, uint16_t current_block_rotation)
   {
     return current_block_rotation;

nebula_decoders/include/nebula_decoders/nebula_decoders_velodyne/decoders/vls_128.hpp

@@ -9,12 +9,16 @@ namespace drivers
 class VLS128 : public VelodyneSensor
 {
 public:
+  // To ignore an empty data blocks in VLS128 case
+  /// @brief VLS128 Dual return mode data structure in VLS128 User manual p.57
   int getNumPaddingBlocks(bool dual_return)
   {
     if (dual_return) return 4;
     return 0;
   }
 
+// calculate and stack the firing timing for each laser timeing
+/// @brief laser timing for VLS128 from VLS128 User manual in p.61
   bool fillAzimuthCache()
   {
     for (uint8_t i = 0; i < 16; i++) {
@@ -23,6 +27,11 @@ class VLS128 : public VelodyneSensor
     return true;
   }
 
+  /// @brief fomula from VLS128 User manual in p.65
+  /// @param azimuth Azimuth angle
+  /// @param azimuth_diff Azimuth difference
+  /// @param firing_order Firing order
+  /// @return Corrected azimuth
   uint16_t getAzimuthCorrected(
     uint16_t azimuth, float azimuth_diff, int /* firing_sequence */, int firing_order)
   {