Method write

src/laswriteitemcompressed_v4.cpp:475–756

}

inline BOOL LASwriteItemCompressed_POINT14_v4::write(const U8* item, U32& context)
{
  // get last

  U8* last_item = contexts[current_context].last_item;

  ////////////////////////////////////////
  // compress returns_XY layer 
  ////////////////////////////////////////

  // create single (3) / first (1) / last (2) / intermediate (0) context from last point return

  I32 lpr = (((LASpoint14*)last_item)->return_number == 1 ? 1 : 0); // first?
  lpr += (((LASpoint14*)last_item)->return_number >= ((LASpoint14*)last_item)->number_of_returns ? 2 : 0); // last?

  // add info whether the GPS time changed in the last return to the context

  lpr += (((LASpoint14*)last_item)->gps_time_change ? 4 : 0);

  // get the (potentially new) context

  U32 scanner_channel = ((const LASpoint14*)item)->scanner_channel;

  // if context has changed (and the new context already exists) get last for new context

  if (scanner_channel != current_context)
  {
    if (contexts[scanner_channel].unused == FALSE)
    {
      last_item = contexts[scanner_channel].last_item;
    }
  }

  // determine changed attributes

  BOOL point_source_change = (((const LASpoint14*)item)->point_source_ID != ((LASpoint14*)last_item)->point_source_ID);
  BOOL gps_time_change = (((const LASpoint14*)item)->gps_time != ((LASpoint14*)last_item)->gps_time);
  BOOL scan_angle_change = (((const LASpoint14*)item)->scan_angle != ((LASpoint14*)last_item)->scan_angle);

  // get last and current return counts

  U32 last_n = ((LASpoint14*)last_item)->number_of_returns;
  U32 last_r = ((LASpoint14*)last_item)->return_number;

  U32 n = ((const LASpoint14*)item)->number_of_returns;
  U32 r = ((const LASpoint14*)item)->return_number;

  // create the 7 bit mask that encodes various changes (its value ranges from 0 to 127)

  I32 changed_values = ((scanner_channel != current_context) << 6) | // scanner channel compared to last point (same = 0 / different = 1)
                       (point_source_change << 5) |                  // point source ID compared to last point from *same* scanner channel (same = 0 / different = 1)
                       (gps_time_change << 4) |                      // GPS time stamp compared to last point from *same* scanner channel (same = 0 / different = 1)
                       (scan_angle_change << 3) |                    // scan angle compared to last point from *same* scanner channel (same = 0 / different = 1)
                       ((n != last_n) << 2);                         // number of returns compared to last point from *same* scanner channel (same = 0 / different = 1)

  // return number compared to last point of *same* scanner channel (same = 0 / plus one mod 16 = 1 / minus one mod 16 = 2 / other difference = 3)

  if (r != last_r)