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#pragma once
#include <util/generic/typelist.h>
#include <util/system/defaults.h>
/*
* original url (now dead): http://www.cris.com/~Ttwang/tech/inthash.htm
* copy: https://gist.github.com/badboy/6267743
*/
static constexpr ui8 IntHashImpl(ui8 key8) noexcept {
size_t key = key8;
key += ~(key << 15);
key ^= (key >> 10);
key += (key << 3);
key ^= (key >> 6);
key += ~(key << 11);
key ^= (key >> 16);
return static_cast<ui8>(key);
}
static constexpr ui16 IntHashImpl(ui16 key16) noexcept {
size_t key = key16;
key += ~(key << 15);
key ^= (key >> 10);
key += (key << 3);
key ^= (key >> 6);
key += ~(key << 11);
key ^= (key >> 16);
return static_cast<ui16>(key);
}
static constexpr ui32 IntHashImpl(ui32 key) noexcept {
key += ~(key << 15);
key ^= (key >> 10);
key += (key << 3);
key ^= (key >> 6);
key += ~(key << 11);
key ^= (key >> 16);
return key;
}
static constexpr ui64 IntHashImpl(ui64 key) noexcept {
key += ~(key << 32);
key ^= (key >> 22);
key += ~(key << 13);
key ^= (key >> 8);
key += (key << 3);
key ^= (key >> 15);
key += ~(key << 27);
key ^= (key >> 31);
return key;
}
template <class T>
static constexpr T IntHash(T t) noexcept {
using TCvt = TFixedWidthUnsignedInt<T>;
return IntHashImpl((TCvt)(t));
}
/*
* can handle floats && pointers
*/
template <class T>
static constexpr size_t NumericHash(T t) noexcept {
using TCvt = TFixedWidthUnsignedInt<T>;
union Y_HIDDEN {
T t;
TCvt cvt;
} u{t};
return (size_t)IntHash(u.cvt);
}
template <class T>
static constexpr T CombineHashes(T l, T r) noexcept {
return IntHash(l) ^ r;
}
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