hash_funcs.h

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#ifndef HASH_FUNCS_H
#define HASH_FUNCS_H
 
#include <functional>
#include <memory>
#include <tuple>
#include <utility>
 
namespace mazes {
 
 
struct uni_hash {
    template <class T1>
    std::size_t operator()(const T1& p) const {
        auto hash1 = std::hash<T1>{}(p);
        auto hash2 = std::hash<T1>{}(p) + 0x9e3779b9;
        return hash1 ^ (hash2 + 0x9e3779b9 + (hash1 << 6) + (hash1 >> 2));
    }
};
 
struct pair_hash {
 
    template <class T1, class T2>
    std::size_t operator()(const std::pair<T1, T2>& p) const {
        auto hash1 = std::hash<T1>{}(p.first);
        auto hash2 = std::hash<T2>{}(p.second);
        return hash1 ^ hash2;
    }
}; // pair_hash
 
struct tri_hash {
    template <class T1, class T2, class T3>
    std::size_t operator()(const std::tuple<T1, T2, T3>& p) const {
        auto hash1 = std::hash<T1>{}(std::get<0>(p));
        auto hash2 = std::hash<T2>{}(std::get<1>(p));
        auto hash3 = std::hash<T3>{}(std::get<2>(p));
        return hash1 ^ hash2 ^ hash3;
    }
};
 
struct weak_ptr_hash {
 
    template <typename T>
    std::size_t operator()(const std::weak_ptr<T>& weak) const {
        if (auto shared = weak.lock()) {
            return std::hash<std::shared_ptr<T>>{}(shared);
        }
 
        // Return 0 for expired weak_ptr
        return 0;
    }
};
 
} // namespace mazes
 
#endif // HASH_FUNCS_H