28 lines
844 B
C++
28 lines
844 B
C++
#ifndef FROZEN_LETITGO_BITS_HASH_STRING_H
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#define FROZEN_LETITGO_BITS_HASH_STRING_H
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#include <cstddef>
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namespace frozen {
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template <typename String>
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constexpr std::size_t hash_string(const String& value) {
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std::size_t d = 5381;
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for (const auto& c : value)
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d = d * 33 + static_cast<std::size_t>(c);
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return d;
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}
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// https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
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// With the lowest bits removed, based on experimental setup.
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template <typename String>
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constexpr std::size_t hash_string(const String& value, std::size_t seed) {
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std::size_t d = (0x811c9dc5 ^ seed) * static_cast<std::size_t>(0x01000193);
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for (const auto& c : value)
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d = (d ^ static_cast<std::size_t>(c)) * static_cast<std::size_t>(0x01000193);
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return d >> 8 ;
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}
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} // namespace frozen
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#endif // FROZEN_LETITGO_BITS_HASH_STRING_H
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