Hash.hpp

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/*
 * Copyright 2024 Nico Reißmann <nico.reissmann@gmail.com>
 * See COPYING for terms of redistribution.
 */
 
#ifndef JLM_UTIL_HASH_HPP
#define JLM_UTIL_HASH_HPP
 
#include <functional>
#include <string_view>
 
namespace jlm::util
{
 
template<typename T>
struct Hash : std::hash<T>
{
};
 
template<typename First, typename Second>
struct Hash<std::pair<First, Second>>
{
  std::size_t
  operator()(const std::pair<First, Second> & value) const noexcept
  {
    return Hash<First>()(value.first) ^ Hash<Second>()(value.second) << 1;
  }
};
 
template<typename... Args>
void
combineHashesWithSeed(std::size_t & seed, std::size_t hash, Args... args)
{
  seed ^= hash + 0x9e3779b9 + (seed << 6) + (seed >> 2);
  (combineHashesWithSeed(seed, args), ...);
}
 
template<typename... Args>
std::size_t
CombineHashes(std::size_t hash, Args... args)
{
  std::size_t seed = 0;
  combineHashesWithSeed(seed, hash, std::forward<Args>(args)...);
  return seed;
}
 
}
 
#endif