blob: da8fc510842b27835d9574b3c67fba93ae5d7062 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
|
#ifndef FROZEN_LETITGO_BITS_HASH_STRING_H
#define FROZEN_LETITGO_BITS_HASH_STRING_H
#include <cstddef>
namespace frozen {
template <typename String>
constexpr std::size_t hash_string(const String& value) {
std::size_t d = 5381;
for (const auto& c : value)
d = d * 33 + static_cast<size_t>(c);
return d;
}
// https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
// With the lowest bits removed, based on experimental setup.
template <typename String>
constexpr std::size_t hash_string(const String& value, std::size_t seed) {
std::size_t d = (0x811c9dc5 ^ seed) * static_cast<size_t>(0x01000193);
for (const auto& c : value)
d = (d ^ static_cast<size_t>(c)) * static_cast<size_t>(0x01000193);
return d >> 8 ;
}
} // namespace frozen
#endif // FROZEN_LETITGO_BITS_HASH_STRING_H
|
