Method Replace

cpp/src/arrow/util/cache_internal.h:74–98

  template <typename K, typename V>
  std::pair<bool, Value*> Replace(K&& key, V&& value) {
    // Try to insert temporary iterator
    auto pair = map_.emplace(std::forward<K>(key), ListIt{});
    const auto it = pair.first;
    const bool inserted = pair.second;
    if (inserted) {
      // Inserted => push item at front of the list, and update iterator
      items_.push_front(Item{&it->first, std::forward<V>(value)});
      it->second = items_.begin();
      // Did we exceed the cache capacity?  If so, remove least recently used item
      if (static_cast<int32_t>(items_.size()) > capacity_) {
        const bool erased = map_.erase(*items_.back().key);
        ARROW_DCHECK(erased);
        ARROW_UNUSED(erased);
        items_.pop_back();
      }
      return {true, &it->second->value};
    } else {
      // Already exists => move item at front of the list, and update value
      auto list_it = it->second;
      items_.splice(items_.begin(), items_, list_it);
      list_it->value = std::forward<V>(value);
      return {false, &list_it->value};
    }
  }

 private:
  struct Item {