Method WriteLevels

cpp/src/parquet/column_writer.cc:1671–1709

  std::shared_ptr<::arrow::Array> preserved_dictionary_;

  int64_t WriteLevels(int64_t num_levels, const int16_t* def_levels,
                      const int16_t* rep_levels) {
    // Update histograms now, to maximize cache efficiency.
    UpdateLevelHistogram(num_levels, def_levels, rep_levels);

    int64_t values_to_write = 0;
    // If the field is required and non-repeated, there are no definition levels
    if (descr_->max_definition_level() > 0) {
      for (int64_t i = 0; i < num_levels; ++i) {
        if (def_levels[i] == descr_->max_definition_level()) {
          ++values_to_write;
        }
      }

      WriteDefinitionLevels(num_levels, def_levels);
    } else {
      // Required field, write all values
      values_to_write = num_levels;
    }

    // Not present for non-repeated fields
    if (descr_->max_repetition_level() > 0) {
      // A row could include more than one value
      // Count the occasions where we start a new row
      for (int64_t i = 0; i < num_levels; ++i) {
        if (rep_levels[i] == 0) {
          rows_written_++;
          num_buffered_rows_++;
        }
      }

      WriteRepetitionLevels(num_levels, rep_levels);
    } else {
      // Each value is exactly one row
      rows_written_ += num_levels;
      num_buffered_rows_ += num_levels;
    }
    return values_to_write;
  }

  // This method will always update the three output parameters,
  // out_values_to_write, out_spaced_values_to_write and null_count.  Additionally