Method RleEncodeLevels

cpp/src/parquet/column_writer.cc:938–965

return the size of the encoded buffer

// return the size of the encoded buffer
int64_t ColumnWriterImpl::RleEncodeLevels(const void* src_buffer,
                                          ResizableBuffer* dest_buffer, int16_t max_level,
                                          bool include_length_prefix) {
  // V1 DataPage includes the length of the RLE level as a prefix.
  int32_t prefix_size = include_length_prefix ? sizeof(int32_t) : 0;

  // TODO: This only works with due to some RLE specifics
  int64_t rle_size = LevelEncoder::MaxBufferSize(Encoding::RLE, max_level,
                                                 static_cast<int>(num_buffered_values_)) +
                     prefix_size;

  // Use Arrow::Buffer::shrink_to_fit = false
  // underlying buffer only keeps growing. Resize to a smaller size does not reallocate.
  PARQUET_THROW_NOT_OK(dest_buffer->Resize(rle_size, false));

  level_encoder_.Init(Encoding::RLE, max_level, static_cast<int>(num_buffered_values_),
                      dest_buffer->mutable_data() + prefix_size,
                      static_cast<int>(dest_buffer->size() - prefix_size));
  int encoded = level_encoder_.Encode(static_cast<int>(num_buffered_values_),
                                      reinterpret_cast<const int16_t*>(src_buffer));
  DCHECK_EQ(encoded, num_buffered_values_);

  if (include_length_prefix) {
    reinterpret_cast<int32_t*>(dest_buffer->mutable_data())[0] = level_encoder_.len();
  }

  return level_encoder_.len() + prefix_size;
}

void ColumnWriterImpl::AddDataPage() {
  int64_t definition_levels_rle_size = 0;