1// Copyright (c) 2016-present 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
10template <class T>
11struct 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 */
23template <class K, class T>
24class indirectmap {
25private:
26    typedef std::map<const K*, T, DereferencingComparator<const K*> > base;
27    base m;
28public:
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    std::pair<iterator, bool> insert(const value_type& value) { return m.insert(value); }
36
37    // pass address (value interface)
38    iterator find(const K& key)                     { return m.find(&key); }
39    const_iterator find(const K& key) const         { return m.find(&key); }
40    iterator lower_bound(const K& key)              { return m.lower_bound(&key); }
41    const_iterator lower_bound(const K& key) const  { return m.lower_bound(&key); }
42    size_type erase(const K& key)                   { return m.erase(&key); }
43    size_type count(const K& key) const             { return m.count(&key); }
44
45    // passthrough
46    bool empty() const              { return m.empty(); }
47    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    iterator end()                  { return m.end(); }
52    const_iterator begin() const    { return m.begin(); }
53    const_iterator end() const      { return m.end(); }
54    const_iterator cbegin() const   { return m.cbegin(); }
55    const_iterator cend() const     { return m.cend(); }
56};
57
58#endif // BITCOIN_INDIRECTMAP_H
59