Hash.hpp

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//
// Aurora C++ Library
// Copyright (c) 2012-2016 Jan Haller
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
//    claim that you wrote the original software. If you use this software
//    in a product, an acknowledgment in the product documentation would be
//    appreciated but is not required.
//
// 2. Altered source versions must be plainly marked as such, and must not be
//    misrepresented as being the original software.
//
// 3. This notice may not be removed or altered from any source distribution.
//


#ifndef AURORA_HASH_HPP
#define AURORA_HASH_HPP

#include <Aurora/Meta/Templates.hpp>

#include <functional>


namespace aurora
{


template <typename T>
std::size_t hashValue(const T& object
    AURORA_ENABLE_IF(!std::is_enum<T>::value))
{
    std::hash<T> hasher;
    return hasher(object);
}

// Overload for enums
template <typename T>
std::size_t hashValue(const T& enumerator
    AURORA_ENABLE_IF(std::is_enum<T>::value))
{
    return hashValue(static_cast<typename std::underlying_type<T>::type>(enumerator));
}

template <typename T>
void hashCombine(std::size_t& seed, const T& object)
{
    // Implementation from Boost.Functional/Hash
    seed ^= hashValue(object) + 0x9e3779b9u + (seed << 6) + (seed >> 2);
}

template <typename Itr>
void hashRange(std::size_t& seed, Itr begin, Itr end)
{
    for (; begin != end; ++begin)
        hashCombine(seed, *begin);
}

struct PairHasher
{
    template <typename T, typename U>
    std::size_t operator() (const std::pair<T, U>& pair) const
    {
        std::size_t hash = 0u;
        hashCombine(hash, pair.first);
        hashCombine(hash, pair.second);

        return hash;
    }
};


} // namespace aurora

#endif // AURORA_HASH_HPP