File indexing completed on 2024-12-08 10:25:49

 /*
    SPDX-FileCopyrightText: 2020 Milian Wolff <mail@milianw.org>
 
    SPDX-License-Identifier: LGPL-2.0-or-later
 */
 
 #pragma once
 
 #include <algorithm>
 #include <vector>
 
 template<typename Key, typename Value>
 class LRUCache
 {
 public:
     struct Entry {
         Key key;
         Value value;
         bool operator==(const Key &rhs) const
         {
             return key == rhs;
         }
     };
     using Entries = std::vector<Entry>;
     using value_type = typename Entries::value_type;
     using size_type = typename Entries::size_type;
     using difference_type = typename Entries::difference_type;
     // only const access
     using reference = typename Entries::const_reference;
     using const_reference = typename Entries::const_reference;
     using pointer = typename Entries::const_pointer;
     using iterator = typename Entries::const_iterator;
     using const_iterator = typename Entries::const_iterator;
 
     void setMaxEntries(int maxEntries)
     {
         mMaxEntries = maxEntries;
     }
 
     std::size_t size() const
     {
         return mEntries.size();
     }
 
     const_iterator begin() const
     {
         return mEntries.begin();
     }
 
     const_iterator end() const
     {
         return std::next(mEntries.begin(), size());
     }
 
     const_iterator find(const Key &key)
     {
         // using non-const iterators here since we will re-insert when we find
         const auto begin = mEntries.begin();
         const auto end = std::next(mEntries.begin(), size());
         auto it = std::find(begin, end, key);
         if (it == begin || it == end) { // not found or already the last recently used one
             return it;
         }
 
         // rotate to mark entry as last recently used one
         std::rotate(begin, it, it + 1);
         return mEntries.cbegin();
     }
 
     void insert(Key key, Value value)
     {
         auto entriesSize = size();
         if (mMaxEntries == -1 || (entriesSize < static_cast<size_t>(mMaxEntries))) {
             // open up a new slot
             ++entriesSize;
             mEntries.resize(entriesSize);
         }
 
         // right shift to make space at the front
         std::rotate(mEntries.begin(), std::next(mEntries.begin(), entriesSize - 1), std::next(mEntries.begin(), entriesSize));
 
         // insert up front
         mEntries.front() = {std::move(key), std::move(value)};
     }
 
     bool remove(const Key &key)
     {
         const auto begin = mEntries.begin();
         const auto end = std::next(mEntries.begin(), size());
         auto it = std::find(begin, end, key);
         if (it == end) { // not found or already the last recently used one
             return false;
         }
 
         std::move(std::next(it), end, it);
         mEntries.resize(size() - 1);
         return true;
     }
 
     void clear()
     {
         mEntries.clear();
     }
 
 private:
     Entries mEntries;
     int mMaxEntries = -1;
 };