Method DoCount

cpp/src/arrow/csv/reader.cc:1194–1208

  }

  Future<int64_t> DoCount(const std::shared_ptr<CSVRowCounter>& self) {
    // count_cb must return a value instead of Status/Future<> to work with
    // MakeMappedGenerator, and it must use a type with a valid end value to work with
    // IterationEnd.
    std::function<Result<std::optional<int64_t>>(const CSVBlock&)> count_cb =
        [self](const CSVBlock& maybe_block) -> Result<std::optional<int64_t>> {
      ARROW_ASSIGN_OR_RAISE(auto parsed_block, self->Parse(maybe_block));
      int32_t total_row_count = parsed_block.parser->total_num_rows();
      self->row_count_ += total_row_count;
      return total_row_count;
    };
    auto count_gen = MakeMappedGenerator(block_generator_, std::move(count_cb));
    return DiscardAllFromAsyncGenerator(count_gen).Then(
        [self]() { return self->row_count_; });
  }

  Executor* cpu_executor_;
  AsyncGenerator<CSVBlock> block_generator_;