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Saves about 10% of application memory usage once the mempool warms up. Since the mempool is DynamicUsage-regulated, this will translate to a larger mempool in the same amount of space. Map value type: eliminate the vin index; no users of the map need to know which input of the transaction is spending the prevout. Map key type: replace the COutPoint with a pointer to a COutPoint. A COutPoint is 36 bytes, but each COutPoint is accessible from the same map entry's value. A trivial DereferencingComparator functor allows indirect map keys, but the resulting syntax is misleading: `map.find(&outpoint)`. Implement an indirectmap that acts as a wrapper to a map that uses a DereferencingComparator, supporting a syntax that accurately reflect the container's semantics: inserts and iterators use pointers since they store pointers and need them to remain constant and dereferenceable, but lookup functions take const references.0.13
Kaz Wesley
9 years ago
6 changed files with 96 additions and 41 deletions
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#ifndef BITCOIN_INDIRECTMAP_H |
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#define BITCOIN_INDIRECTMAP_H |
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template <class T> |
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struct DereferencingComparator { bool operator()(const T a, const T b) const { return *a < *b; } }; |
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/* Map whose keys are pointers, but are compared by their dereferenced values.
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* |
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* Differs from a plain std::map<const K*, T, DereferencingComparator<K*> > in |
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* that methods that take a key for comparison take a K rather than taking a K* |
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* (taking a K* would be confusing, since it's the value rather than the address |
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* of the object for comparison that matters due to the dereferencing comparator). |
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* |
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* Objects pointed to by keys must not be modified in any way that changes the |
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* result of DereferencingComparator. |
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*/ |
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template <class K, class T> |
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class indirectmap { |
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private: |
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typedef std::map<const K*, T, DereferencingComparator<const K*> > base; |
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base m; |
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public: |
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typedef typename base::iterator iterator; |
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typedef typename base::const_iterator const_iterator; |
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typedef typename base::size_type size_type; |
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typedef typename base::value_type value_type; |
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// passthrough (pointer interface)
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std::pair<iterator, bool> insert(const value_type& value) { return m.insert(value); } |
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// pass address (value interface)
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iterator find(const K& key) { return m.find(&key); } |
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const_iterator find(const K& key) const { return m.find(&key); } |
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iterator lower_bound(const K& key) { return m.lower_bound(&key); } |
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const_iterator lower_bound(const K& key) const { return m.lower_bound(&key); } |
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size_type erase(const K& key) { return m.erase(&key); } |
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size_type count(const K& key) const { return m.count(&key); } |
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// passthrough
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bool empty() const { return m.empty(); } |
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size_type size() const { return m.size(); } |
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size_type max_size() const { return m.max_size(); } |
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void clear() { m.clear(); } |
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iterator begin() { return m.begin(); } |
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iterator end() { return m.end(); } |
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const_iterator begin() const { return m.begin(); } |
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const_iterator end() const { return m.end(); } |
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const_iterator cbegin() const { return m.cbegin(); } |
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const_iterator cend() const { return m.cend(); } |
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}; |
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#endif // BITCOIN_INDIRECTMAP_H
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