Method AddTask

cpp/src/arrow/util/async_util.cc:425–445

  }

  bool AddTask(std::unique_ptr<Task> task) override {
    state_->task_count++;
    struct WrapperTask : public Task {
      WrapperTask(std::unique_ptr<Task> target, std::shared_ptr<State> state)
          : target(std::move(target)), state(std::move(state)) {}
      Result<Future<>> operator()() override {
        ARROW_ASSIGN_OR_RAISE(Future<> inner_fut, (*target)());
        return inner_fut.Then([state = std::move(state)]() {
          if (--state->task_count == 0) {
            return std::move(state->finish_cb)();
          }
          return Status::OK();
        });
      }
      int cost() const override { return target->cost(); }
      std::string_view name() const override { return target->name(); }
      std::unique_ptr<Task> target;
      std::shared_ptr<State> state;
    };
    return target_->AddTask(std::make_unique<WrapperTask>(std::move(task), state_));
  }

  const util::tracing::Span& span() const override { return target_->span(); }