Hash.h

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#ifndef Hash_H
#define Hash_H
 
#include <vector>
 
namespace SVF
{
 
template <class T> struct Hash;
 
template <class S, class T> struct Hash<std::pair<S, T>>
{
    // Pairing function from: http://szudzik.com/ElegantPairing.pdf
    static size_t szudzik(size_t a, size_t b)
    {
        return a > b ? b * b + a : a * a + a + b;
    }
 
    size_t operator()(const std::pair<S, T>& t) const
    {
        Hash<decltype(t.first)> first;
        Hash<decltype(t.second)> second;
        return szudzik(first(t.first), second(t.second));
    }
};
 
template <class T> struct Hash
{
    size_t operator()(const T& t) const
    {
        std::hash<T> h;
        return h(t);
    }
};
 
}  // namespace SVF
 
template <typename T> struct std::hash<std::vector<T>>
{
    size_t operator()(const std::vector<T>& v) const
    {
        // TODO: repetition with CBV.
        size_t h = v.size();
 
        SVF::Hash<T> hf;
        for (const T& t : v)
        {
            h ^= hf(t) + 0x9e3779b9 + (h << 6) + (h >> 2);
        }
 
        return h;
    }
};
 
#endif // Hash_H