text: // Copyright (c) 2012 The ZcoinDark developers
  // Distributed under the MIT/X11 software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  #ifndef BITCOIN_MRUSET_H
  #define BITCOIN_MRUSET_H
  
  #include <set>
  #include <deque>
  
  /** STL-like set container that only keeps the most recent N elements. */
  template <typename T> class mruset
  {
  public:
      typedef T key_type;
      typedef T value_type;
      typedef typename std::set<T>::iterator iterator;
      typedef typename std::set<T>::const_iterator const_iterator;
      typedef typename std::set<T>::size_type size_type;
  
  protected:
      std::set<T> set;
      std::deque<T> queue;
      size_type nMaxSize;
  
  public:
      mruset(size_type nMaxSizeIn = 0) { nMaxSize = nMaxSizeIn; }
      iterator begin() const { return set.begin(); }
      iterator end() const { return set.end(); }
      size_type size() const { return set.size(); }
      bool empty() const { return set.empty(); }
      iterator find(const key_type& k) const { return set.find(k); }
      size_type count(const key_type& k) const { return set.count(k); }
      bool inline friend operator==(const mruset<T>& a, const mruset<T>& b) { return a.set == b.set; }
      bool inline friend operator==(const mruset<T>& a, const std::set<T>& b) { return a.set == b; }
      bool inline friend operator<(const mruset<T>& a, const mruset<T>& b) { return a.set < b.set; }
      std::pair<iterator, bool> insert(const key_type& x)
      {
          std::pair<iterator, bool> ret = set.insert(x);
          if (ret.second)
          {
              if (nMaxSize && queue.size() == nMaxSize)
              {
                  set.erase(queue.front());
                  queue.pop_front();
              }
              queue.push_back(x);
          }
          return ret;
      }
      size_type max_size() const { return nMaxSize; }
      size_type max_size(size_type s)
      {
          if (s)
              while (queue.size() > s)
              {
                  set.erase(queue.front());
                  queue.pop_front();
              }
          nMaxSize = s;
          return nMaxSize;
      }
  };
  
  #endif
  