27 lines
787 B
C++
27 lines
787 B
C++
#pragma once
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#include <cstddef>
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namespace basalt {
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// to work around static_assert(false, ...)
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template <class T>
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struct dependent_false : std::false_type {};
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template <class T>
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inline void hash_combine(std::size_t& seed, const T& value) {
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// Simple hash_combine, see e.g. here:
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// https://github.com/HowardHinnant/hash_append/issues/7
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// Not sure we ever need 32bit, but here it is...
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if constexpr (sizeof(std::size_t) == 4) {
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seed ^= std::hash<T>{}(value) + 0x9e3779b9U + (seed << 6) + (seed >> 2);
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} else if constexpr (sizeof(std::size_t) == 8) {
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seed ^= std::hash<T>{}(value) + 0x9e3779b97f4a7c15LLU + (seed << 12) +
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(seed >> 4);
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} else {
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static_assert(dependent_false<T>::value, "hash_combine not implemented");
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}
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}
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} // namespace basalt
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