Method read

LASzip/src/lasreaditemcompressed_v4.cpp:709–1002

}

inline void LASreadItemCompressed_POINT14_v4::read(U8* item, U32& context)
{
  // get last

  U8* last_item = contexts[current_context].last_item;

  ////////////////////////////////////////
  // decompress 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);

  // decompress which values have changed with last point return context

  I32 changed_values = dec_channel_returns_XY->decodeSymbol(contexts[current_context].m_changed_values[lpr]);

  // if scanner channel has changed

  if (changed_values & (1 << 6))
  {
    U32 diff = dec_channel_returns_XY->decodeSymbol(contexts[current_context].m_scanner_channel); // curr = last + (sym + 1)
    U32 scanner_channel = (current_context + diff + 1) % 4;
    // maybe create and init entropy models and integer compressors
    if (contexts[scanner_channel].unused)
    {
      // create and init entropy models and integer decompressors
      createAndInitModelsAndDecompressors(scanner_channel, contexts[current_context].last_item);
    }
    // switch context to current scanner channel
    current_context = scanner_channel;

    // get last for new context
    last_item = contexts[current_context].last_item;
    ((LASpoint14*)last_item)->scanner_channel = scanner_channel;
  }
  context = current_context; // the POINT14 reader sets context for all other items

  // determine changed attributes

  BOOL point_source_change = (changed_values & (1 << 5) ? TRUE : FALSE);
  BOOL gps_time_change = (changed_values & (1 << 4) ? TRUE : FALSE);
  BOOL scan_angle_change = (changed_values & (1 << 3) ? TRUE : FALSE);

  // get last return counts

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

  // if number of returns is different we decompress it

  U32 n;