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// Copyright (c) 2012-2015 The Bitcoin Core developers
// Distributed under the MIT 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 <vector>
#include <utility>
/** 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::vector<iterator> order;
size_type first_used;
size_type first_unused;
const size_type nMaxSize;
public:
mruset(size_type nMaxSizeIn = 1) : nMaxSize(nMaxSizeIn) { clear(); }
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); }
void clear()
{
set.clear();
order.assign(nMaxSize, set.end());
first_used = 0;
first_unused = 0;
}
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 (set.size() == nMaxSize + 1) {
set.erase(order[first_used]);
order[first_used] = set.end();
if (++first_used == nMaxSize) first_used = 0;
}
order[first_unused] = ret.first;
if (++first_unused == nMaxSize) first_unused = 0;
}
return ret;
}
size_type max_size() const { return nMaxSize; }
};
#endif // BITCOIN_MRUSET_H
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