Method Convert

cpp/src/arrow/json/converter.cc:238–276

  using PrimitiveConverter::PrimitiveConverter;

  Status Convert(const std::shared_ptr<Array>& in, std::shared_ptr<Array>* out) override {
    if (in->type_id() == Type::NA) {
      return MakeArrayOfNull(out_type_, in->length(), pool_).Value(out);
    }
    const auto& dict_array = GetDictionaryArray(in);

    using Builder = typename TypeTraits<T>::BuilderType;
    Builder builder(out_type_, pool_);
    RETURN_NOT_OK(builder.Resize(dict_array.indices()->length()));

    // TODO(bkietz) this can be computed during parsing at low cost
    int64_t data_length = 0;
    auto visit_lengths_valid = [&](string_view value) {
      data_length += value.size();
      return Status::OK();
    };

    auto visit_lengths_null = [&]() {
      // no-op
      return Status::OK();
    };

    RETURN_NOT_OK(
        VisitDictionaryEntries(dict_array, visit_lengths_valid, visit_lengths_null));
    RETURN_NOT_OK(builder.ReserveData(data_length));

    auto visit_valid = [&](string_view value) {
      builder.UnsafeAppend(value);
      return Status::OK();
    };

    auto visit_null = [&]() {
      builder.UnsafeAppendNull();
      return Status::OK();
    };

    RETURN_NOT_OK(VisitDictionaryEntries(dict_array, visit_valid, visit_null));
    return builder.Finish(out);
  }
};

Status MakeConverter(const std::shared_ptr<DataType>& out_type, MemoryPool* pool,