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       1                 :            : // Copyright (c) 2016-2020 The Bitcoin Core developers
       2                 :            : // Distributed under the MIT software license, see the accompanying
       3                 :            : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       4                 :            : 
       5                 :            : #ifndef BITCOIN_INDIRECTMAP_H
       6                 :            : #define BITCOIN_INDIRECTMAP_H
       7                 :            : 
       8                 :            : #include <map>
       9                 :            : 
      10                 :            : template <class T>
      11                 :          0 : struct DereferencingComparator { bool operator()(const T a, const T b) const { return *a < *b; } };
      12                 :            : 
      13                 :            : /* Map whose keys are pointers, but are compared by their dereferenced values.
      14                 :            :  *
      15                 :            :  * Differs from a plain std::map<const K*, T, DereferencingComparator<K*> > in
      16                 :            :  * that methods that take a key for comparison take a K rather than taking a K*
      17                 :            :  * (taking a K* would be confusing, since it's the value rather than the address
      18                 :            :  * of the object for comparison that matters due to the dereferencing comparator).
      19                 :            :  *
      20                 :            :  * Objects pointed to by keys must not be modified in any way that changes the
      21                 :            :  * result of DereferencingComparator.
      22                 :            :  */
      23                 :            : template <class K, class T>
      24                 :            : class indirectmap {
      25                 :            : private:
      26                 :            :     typedef std::map<const K*, T, DereferencingComparator<const K*> > base;
      27                 :            :     base m;
      28                 :            : public:
      29                 :            :     typedef typename base::iterator iterator;
      30                 :            :     typedef typename base::const_iterator const_iterator;
      31                 :            :     typedef typename base::size_type size_type;
      32                 :            :     typedef typename base::value_type value_type;
      33                 :            : 
      34                 :            :     // passthrough (pointer interface)
      35                 :          0 :     std::pair<iterator, bool> insert(const value_type& value) { return m.insert(value); }
      36                 :            : 
      37                 :            :     // pass address (value interface)
      38                 :          1 :     iterator find(const K& key)                     { return m.find(&key); }
      39                 :          0 :     const_iterator find(const K& key) const         { return m.find(&key); }
      40                 :          0 :     iterator lower_bound(const K& key)              { return m.lower_bound(&key); }
      41                 :          0 :     const_iterator lower_bound(const K& key) const  { return m.lower_bound(&key); }
      42                 :          0 :     size_type erase(const K& key)                   { return m.erase(&key); }
      43                 :          0 :     size_type count(const K& key) const             { return m.count(&key); }
      44                 :            : 
      45                 :            :     // passthrough
      46                 :            :     bool empty() const              { return m.empty(); }
      47                 :          3 :     size_type size() const          { return m.size(); }
      48                 :            :     size_type max_size() const      { return m.max_size(); }
      49                 :            :     void clear()                    { m.clear(); }
      50                 :            :     iterator begin()                { return m.begin(); }
      51                 :          1 :     iterator end()                  { return m.end(); }
      52                 :            :     const_iterator begin() const    { return m.begin(); }
      53                 :          0 :     const_iterator end() const      { return m.end(); }
      54                 :          1 :     const_iterator cbegin() const   { return m.cbegin(); }
      55                 :          1 :     const_iterator cend() const     { return m.cend(); }
      56                 :            : };
      57                 :            : 
      58                 :            : #endif // BITCOIN_INDIRECTMAP_H