Method Converter_Dictionary

r/src/array_to_vector.cpp:571–615

 public:
  explicit Converter_Dictionary(const std::shared_ptr<ChunkedArray>& chunked_array)
      : Converter(chunked_array),
        need_unification_(DictionaryChunkArrayNeedUnification(chunked_array)) {
    if (need_unification_) {
      const auto& arr_type = checked_cast<const DictionaryType&>(*chunked_array->type());
      unifier_ = ValueOrStop(DictionaryUnifier::Make(arr_type.value_type()));

      int n_arrays = chunked_array->num_chunks();
      arrays_transpose_.resize(n_arrays);

      for (int i = 0; i < n_arrays; i++) {
        const auto& dict_i =
            *checked_cast<const DictionaryArray&>(*chunked_array->chunk(i)).dictionary();
        StopIfNotOk(unifier_->Unify(dict_i, &arrays_transpose_[i]));
      }

      StopIfNotOk(unifier_->GetResult(&out_type_, &dictionary_));
    } else {
      const auto& dict_type = checked_cast<const DictionaryType&>(*chunked_array->type());

      const auto& indices_type = *dict_type.index_type();
      switch (indices_type.id()) {
        case Type::UINT8:
        case Type::INT8:
        case Type::UINT16:
        case Type::INT16:
        case Type::INT32:
          // TODO: also add int64, uint32, uint64 downcasts, if possible
          break;
        default:
          cpp11::stop("Cannot convert Dictionary Array of type `%s` to R",
                      dict_type.ToString().c_str());
      }

      if (chunked_array->num_chunks() > 0) {
        // DictionaryChunkArrayNeedUnification() returned false so we can safely assume
        // the dictionary of the first chunk applies everywhere
        const auto& dict_array =
            checked_cast<const DictionaryArray&>(*chunked_array->chunk(0));
        dictionary_ = dict_array.dictionary();
      } else {
        dictionary_ = CreateEmptyArray(dict_type.value_type());
      }
    }
  }

  SEXP Allocate(R_xlen_t n) const {
    cpp11::writable::integers data(n);