Function FillZeroLengthArray

cpp/src/arrow/array/data.cc:384–414

namespace internal {

void FillZeroLengthArray(const DataType* type, ArraySpan* span) {
  span->type = type;
  span->length = 0;
  int num_buffers = GetNumBuffers(*type);
  for (int i = 0; i < num_buffers; ++i) {
    alignas(int64_t) static std::array<uint8_t, sizeof(int64_t) * 2> kZeros{0};
    span->buffers[i].data = kZeros.data();
    span->buffers[i].size = 0;
  }

  if (!may_have_validity_bitmap(type->id())) {
    span->buffers[0] = {};
  }

  for (int i = num_buffers; i < 3; ++i) {
    span->buffers[i] = {};
  }

  if (type->id() == Type::DICTIONARY) {
    span->child_data.resize(1);
    const std::shared_ptr<DataType>& value_type =
        checked_cast<const DictionaryType*>(type)->value_type();
    FillZeroLengthArray(value_type.get(), &span->child_data[0]);
  } else {
    // Fill children
    span->child_data.resize(type->num_fields());
    for (int i = 0; i < type->num_fields(); ++i) {
      FillZeroLengthArray(type->field(i)->type().get(), &span->child_data[i]);
    }
  }
}

}  // namespace internal