poppler/PopplerCache.h

//========================================================================
//
// PopplerCache.h
//
// This file is licensed under the GPLv2 or later
//
// Copyright (C) 2009 Koji Otani <sho@bbr.jp>
// Copyright (C) 2009, 2010, 2017, 2018 Albert Astals Cid <aacid@kde.org>
// Copyright (C) 2010 Carlos Garcia Campos <carlosgc@gnome.org>
// Copyright (C) 2018 Adam Reichold <adam.reichold@t-online.de>
//
//========================================================================

#ifndef POPPLER_CACHE_H
#define POPPLER_CACHE_H

#include <algorithm>
#include <memory>
#include <utility>
#include <vector>

template<typename Key, typename Item>
class PopplerCache
{
public:
  PopplerCache(const PopplerCache &) = delete;
  PopplerCache& operator=(const PopplerCache &other) = delete;

  PopplerCache(std::size_t cacheSizeA) { entries.reserve(cacheSizeA); }

  /* The item returned is owned by the cache */
  Item *lookup(const Key &key) {
    if (!entries.empty() && entries.front().first == key) {
      return entries.front().second.get();
    }

    for (auto it = entries.begin(); it != entries.end(); ++it) {
      if (it->first == key) {
	auto *item = it->second.get();

	std::rotate(entries.begin(), it, std::next(it));

	return item;
      }
    }

    return nullptr;
  }
    
  /* The key and item pointers ownership is taken by the cache */
  void put(const Key &key, Item *item) {
    if (entries.size() == entries.capacity()) {
      entries.pop_back();
    }

    entries.emplace(entries.begin(), key, std::unique_ptr<Item>{item});
  }

private:
  std::vector<std::pair<Key, std::unique_ptr<Item>>> entries;
};

#endif