Cache transaction validation successes

Conflicts:
	src/main.cpp
	src/test/test_bitcoin.cpp

Github-Pull: #6077
Rebased-From: 17b11428c135203342aff38cabc8047e673f38ac 517e6dd25618522c716e64859554b0f29c6e65d0

src/mruset.h

@@ -9,6 +9,10 @@
 #include <vector>
 #include <utility>
 
+#include <boost/multi_index_container.hpp>
+#include <boost/multi_index/ordered_index.hpp>
+#include <boost/multi_index/sequenced_index.hpp>
+
 /** STL-like set container that only keeps the most recent N elements. */
 template <typename T>
 class mruset
@@ -62,4 +66,60 @@ public:
     size_type max_size() const { return nMaxSize; }
 };
 
+/** STL-like map container that only keeps the most recent N elements. */
+template <typename K, typename V>
+class mrumap
+{
+private:
+    struct key_extractor {
+        typedef K result_type;
+        const result_type& operator()(const std::pair<K, V>& e) const { return e.first; }
+        result_type& operator()(std::pair<K, V>* e) const { return e->first; }
+    };
+
+    typedef boost::multi_index_container<
+        std::pair<K, V>,
+        boost::multi_index::indexed_by<
+            boost::multi_index::sequenced<>,
+            boost::multi_index::ordered_unique<key_extractor>
+        >
+    > map_type;
+
+public:
+    typedef K key_type;
+    typedef std::pair<K, V> value_type;
+    typedef typename map_type::iterator iterator;
+    typedef typename map_type::const_iterator const_iterator;
+    typedef typename map_type::size_type size_type;
+
+protected:
+    map_type m_;
+    size_type max_size_;
+
+public:
+    mrumap(size_type max_size_in = 1) { clear(max_size_in); }
+    iterator begin() { return m_.begin(); }
+    iterator end() { return m_.end(); }
+    const_iterator begin() const { return m_.begin(); }
+    const_iterator end() const { return m_.end(); }
+    size_type size() const { return m_.size(); }
+    bool empty() const { return m_.empty(); }
+    iterator find(const key_type& key) { return m_.template project<0>(boost::get<1>(m_).find(key)); }
+    const_iterator find(const key_type& key) const { return m_.template project<0>(boost::get<1>(m_).find(key)); }
+    size_type count(const key_type& key) const { return boost::get<1>(m_).count(key); }
+    void clear(size_type max_size_in) { m_.clear(); max_size_ = max_size_in; }
+    std::pair<iterator, bool> insert(const K& key, const V& value) 
+    {
+        std::pair<K, V> elem(key, value);
+        std::pair<iterator, bool> p = m_.push_front(elem);
+        if (p.second && m_.size() > max_size_) {
+            m_.pop_back();
+        }
+        return p;
+    }
+    void erase(iterator it) { m_.erase(it); }
+    void erase(const key_type& k) { boost::get<1>(m_).erase(k); }
+    size_type max_size() const { return max_size_; }
+};
+
 #endif // BITCOIN_MRUSET_H