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#pragma once
#include <util/generic/utility.h>
#include <util/generic/strbuf.h>
#include <utility>
// NOTE: These functions provide CityHash 1.0 implementation whose results are *different* from
// the mainline version of CityHash.
using uint128 = std::pair<ui64, ui64>;
constexpr ui64 Uint128Low64(const uint128& x) {
return x.first;
}
constexpr ui64 Uint128High64(const uint128& x) {
return x.second;
}
// Hash functions for a byte array.
// http://en.wikipedia.org/wiki/CityHash
Y_PURE_FUNCTION ui64 CityHash64(const char* buf, size_t len) noexcept;
Y_PURE_FUNCTION ui64 CityHash64WithSeed(const char* buf, size_t len, ui64 seed) noexcept;
Y_PURE_FUNCTION ui64 CityHash64WithSeeds(const char* buf, size_t len, ui64 seed0, ui64 seed1) noexcept;
Y_PURE_FUNCTION uint128 CityHash128(const char* s, size_t len) noexcept;
Y_PURE_FUNCTION uint128 CityHash128WithSeed(const char* s, size_t len, uint128 seed) noexcept;
// Hash 128 input bits down to 64 bits of output.
// This is intended to be a reasonably good hash function.
inline ui64 Hash128to64(const uint128& x) {
// Murmur-inspired hashing.
const ui64 kMul = 0x9ddfea08eb382d69ULL;
ui64 a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;
a ^= (a >> 47);
ui64 b = (Uint128High64(x) ^ a) * kMul;
b ^= (b >> 47);
b *= kMul;
return b;
}
namespace NPrivateCityHash {
template <class TStringType>
inline TStringBuf GetBufFromStr(const TStringType& str) {
static_assert(std::is_integral<std::remove_reference_t<decltype(*str.data())>>::value, "invalid type passed to hash function");
return TStringBuf(reinterpret_cast<const char*>(str.data()), (str.size()) * sizeof(*str.data()));
}
}
template <class TStringType>
inline ui64 CityHash64(const TStringType& str) {
TStringBuf buf = NPrivateCityHash::GetBufFromStr(str);
return CityHash64(buf.data(), buf.size());
}
template <class TStringType>
inline ui64 CityHash64WithSeeds(const TStringType& str, ui64 seed0, ui64 seed1) {
TStringBuf buf = NPrivateCityHash::GetBufFromStr(str);
return CityHash64WithSeeds(buf.data(), buf.size(), seed0, seed1);
}
template <class TStringType>
inline ui64 CityHash64WithSeed(const TStringType& str, ui64 seed) {
TStringBuf buf = NPrivateCityHash::GetBufFromStr(str);
return CityHash64WithSeed(buf.data(), buf.size(), seed);
}
template <class TStringType>
inline uint128 CityHash128(const TStringType& str) {
TStringBuf buf = NPrivateCityHash::GetBufFromStr(str);
return CityHash128(buf.data(), buf.size());
}
template <class TStringType>
inline uint128 CityHash128WithSeed(const TStringType& str, uint128 seed) {
TStringBuf buf = NPrivateCityHash::GetBufFromStr(str);
return CityHash128WithSeed(buf.data(), buf.size(), seed);
}
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