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// SPDX-FileCopyrightText: 2005-2014 Daniel James
// SPDX-FileCopyrightText: 2016 Austin Appleby
// SPDX-License-Identifier: BSL-1.0
#include <array>
#include <climits>
#include <cstdint>
#include <limits>
#include <type_traits>
#include <vector>
namespace Common {
namespace detail {
template <typename T>
requires std::is_unsigned_v<T>
inline std::size_t HashValue(T val) {
const unsigned int size_t_bits = std::numeric_limits<std::size_t>::digits;
const unsigned int length =
(std::numeric_limits<T>::digits - 1) / static_cast<unsigned int>(size_t_bits);
std::size_t seed = 0;
for (unsigned int i = length * size_t_bits; i > 0; i -= size_t_bits) {
seed ^= static_cast<size_t>(val >> i) + (seed << 6) + (seed >> 2);
}
seed ^= static_cast<size_t>(val) + (seed << 6) + (seed >> 2);
return seed;
}
template <size_t Bits>
struct HashCombineImpl {
template <typename T>
static inline T fn(T seed, T value) {
seed ^= value + 0x9e3779b9 + (seed << 6) + (seed >> 2);
return seed;
}
};
template <>
struct HashCombineImpl<64> {
static inline std::uint64_t fn(std::uint64_t h, std::uint64_t k) {
const std::uint64_t m = (std::uint64_t(0xc6a4a793) << 32) + 0x5bd1e995;
const int r = 47;
k *= m;
k ^= k >> r;
k *= m;
h ^= k;
h *= m;
// Completely arbitrary number, to prevent 0's
// from hashing to 0.
h += 0xe6546b64;
return h;
}
};
} // namespace detail
template <typename T>
inline void HashCombine(std::size_t& seed, const T& v) {
seed = detail::HashCombineImpl<sizeof(std::size_t) * CHAR_BIT>::fn(seed, detail::HashValue(v));
}
template <typename It>
inline std::size_t HashRange(It first, It last) {
std::size_t seed = 0;
for (; first != last; ++first) {
HashCombine<typename std::iterator_traits<It>::value_type>(seed, *first);
}
return seed;
}
template <typename T, size_t Size>
std::size_t HashValue(const std::array<T, Size>& v) {
return HashRange(v.cbegin(), v.cend());
}
template <typename T, typename Allocator>
std::size_t HashValue(const std::vector<T, Allocator>& v) {
return HashRange(v.cbegin(), v.cend());
}
} // namespace Common
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