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50 lines
1.7 KiB
C++
50 lines
1.7 KiB
C++
#pragma once
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#include <cstddef>
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#include <functional>
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namespace prometheus {
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namespace detail {
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/// \brief Combine a hash value with nothing.
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/// It's the boundary condition of this serial functions.
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///
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/// \param seed Not effect.
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inline void hash_combine(std::size_t *) {}
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/// \brief Combine the given hash value with another obeject.
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///
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/// \param seed The given hash value. It's a input/output parameter.
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/// \param value The object that will be combined with the given hash value.
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template <typename T>
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inline void hash_combine(std::size_t *seed, const T &value) {
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*seed ^= std::hash<T>{}(value) + 0x9e3779b9 + (*seed << 6) + (*seed >> 2);
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}
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/// \brief Combine the given hash value with another objects. It's a recursion。
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///
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/// \param seed The give hash value. It's a input/output parameter.
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/// \param value The object that will be combined with the given hash value.
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/// \param args The objects that will be combined with the given hash value.
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template <typename T, typename... Types>
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inline void hash_combine(std::size_t *seed, const T &value,
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const Types &...args) {
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hash_combine(seed, value);
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hash_combine(seed, args...);
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}
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/// \brief Compute a hash value of the given args.
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///
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/// \param args The arguments that will be computed hash value.
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/// \return The hash value of the given args.
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template <typename... Types>
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inline std::size_t hash_value(const Types &...args) {
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std::size_t seed = 0;
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hash_combine(&seed, args...);
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return seed;
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}
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} // namespace detail
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} // namespace prometheus
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