Hash.h

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#pragma once
 
#include <string_view>
 
namespace nc::utility
{
namespace detail
{
constexpr size_t FnvOffsetBasis = 14695981039346656037ull;
constexpr size_t FnvPrime = 1099511628211ull;
}
constexpr auto Fnv1a(std::string_view path) -> size_t
{
    auto hash = detail::FnvOffsetBasis;
    for(auto c : path)
    {
        hash = (hash ^ static_cast<uint8_t>(c)) * detail::FnvPrime;
    }
    return hash;
}
 
class StringHash
{
    public:
        constexpr explicit StringHash(std::string_view path)
            : m_hash{Fnv1a(path)}
        {
        }
 
        constexpr auto Hash() const noexcept -> size_t
        {
            return m_hash;
        }
 
    private:
        size_t m_hash;
};
 
constexpr bool operator==(StringHash lhs, StringHash rhs)
{
    return lhs.Hash() == rhs.Hash();
}
 
constexpr bool operator!=(StringHash lhs, StringHash rhs)
{
    return !(lhs == rhs);
}
} // namespace nc::hash