third_party/blink/renderer/core/html/collection_items_cache.h

/*
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 * Copyright (C) 2014 Apple Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions are
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 * notice, this list of conditions and the following disclaimer.
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 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
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#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_HTML_COLLECTION_ITEMS_CACHE_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_HTML_COLLECTION_ITEMS_CACHE_H_

#include "third_party/blink/renderer/core/dom/collection_index_cache.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"

namespace blink {

template <typename Collection, typename NodeType>
class CollectionItemsCache : public CollectionIndexCache<Collection, NodeType> {
  DISALLOW_NEW();

  typedef CollectionIndexCache<Collection, NodeType> Base;

 public:
  CollectionItemsCache();
  ~CollectionItemsCache();

  void Trace(Visitor* visitor) override {
    visitor->Trace(cached_list_);
    Base::Trace(visitor);
  }

  unsigned NodeCount(const Collection&);
  NodeType* NodeAt(const Collection&, unsigned index);
  void Invalidate();

 private:
  bool list_valid_;
  HeapVector<Member<NodeType>> cached_list_;
};

template <typename Collection, typename NodeType>
CollectionItemsCache<Collection, NodeType>::CollectionItemsCache()
    : list_valid_(false) {}

template <typename Collection, typename NodeType>
CollectionItemsCache<Collection, NodeType>::~CollectionItemsCache() = default;

template <typename Collection, typename NodeType>
void CollectionItemsCache<Collection, NodeType>::Invalidate() {
  Base::Invalidate();
  if (list_valid_) {
    cached_list_.Shrink(0);
    list_valid_ = false;
  }
}

template <class Collection, class NodeType>
unsigned CollectionItemsCache<Collection, NodeType>::NodeCount(
    const Collection& collection) {
  if (this->IsCachedNodeCountValid())
    return this->CachedNodeCount();

  NodeType* current_node = collection.TraverseToFirst();
  unsigned current_index = 0;
  while (current_node) {
    cached_list_.push_back(current_node);
    current_node = collection.TraverseForwardToOffset(
        current_index + 1, *current_node, current_index);
  }

  this->SetCachedNodeCount(cached_list_.size());
  list_valid_ = true;
  return this->CachedNodeCount();
}

template <typename Collection, typename NodeType>
inline NodeType* CollectionItemsCache<Collection, NodeType>::NodeAt(
    const Collection& collection,
    unsigned index) {
  if (list_valid_) {
    DCHECK(this->IsCachedNodeCountValid());
    return index < this->CachedNodeCount() ? cached_list_[index] : nullptr;
  }
  return Base::NodeAt(collection, index);
}

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_HTML_COLLECTION_ITEMS_CACHE_H_