drinkingtea/nostalgia
2
0
Fork 0
Code Issues 4 Pull Requests Actions Releases 12 Activity
Files
c6fdf19055ae541107a5ee2bf65ba5332bc511de
nostalgia/deps/ox/deps/cityhash/include/cityhash/city.h

684 lines
23 KiB
C++
Raw Blame History

// Copyright (c) 2011 Google, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
// CityHash, by Geoff Pike and Jyrki Alakuijala
//
// http://code.google.com/p/cityhash/
//
// This file provides a few functions for hashing strings. All of them are
// high-quality functions in the sense that they pass standard tests such
// as Austin Appleby's SMHasher. They are also fast.
//
// For 64-bit x86 code, on short strings, we don't know of anything faster than
// CityHash64 that is of comparable quality. We believe our nearest competitor
// is Murmur3. For 64-bit x86 code, CityHash64 is an excellent choice for hash
// tables and most other hashing (excluding cryptography).
//
// For 64-bit x86 code, on long strings, the picture is more complicated.
// On many recent Intel CPUs, such as Nehalem, Westmere, Sandy Bridge, etc.,
// CityHashCrc128 appears to be faster than all competitors of comparable
// quality. CityHash128 is also good but not quite as fast. We believe our
// nearest competitor is Bob Jenkins' Spooky. We don't have great data for
// other 64-bit CPUs, but for long strings we know that Spooky is slightly
// faster than CityHash on some relatively recent AMD x86-64 CPUs, for example.
// Note that CityHashCrc128 is declared in citycrc.h.
//
// For 32-bit x86 code, we don't know of anything faster than CityHash32 that
// is of comparable quality. We believe our nearest competitor is Murmur3A.
// (On 64-bit CPUs, it is typically faster to use the other CityHash variants.)
//
// Functions in the CityHash family are not suitable for cryptography.
//
// Please see CityHash's README file for more details on our performance
// measurements and so on.
//
// WARNING: This code has been only lightly tested on big-endian platforms!
// It is known to work well on little-endian platforms that have a small penalty
// for unaligned reads, such as current Intel and AMD moderate-to-high-end CPUs.
// It should work on all 32-bit and 64-bit platforms that allow unaligned reads;
// bug reports are welcome.
//
// By the way, for some hash functions, given strings a and b, the hash
// of a+b is easily derived from the hashes of a and b. This property
// doesn't hold for any hash functions in this file.
#ifndef CITY_HASH_H_
#define CITY_HASH_H_
#if __has_include(<cstdint>)
#include <cstdint>
#else
typedef signed char int8_t;
typedef unsigned char uint8_t;
typedef short int16_t;
typedef unsigned short uint16_t;
typedef int int32_t;
typedef unsigned int uint32_t;
typedef unsigned uint_t;
#if defined(__arm__) || defined(__ppc__)
typedef long long int64_t;
typedef unsigned long long uint64_t;
typedef __INTMAX_TYPE__ intmax_t;
typedef __UINTMAX_TYPE__ uintmax_t;
#else
typedef long int64_t;
typedef unsigned long uint64_t;
typedef int64_t intmax_t;
typedef uint64_t uintmax_t;
#endif
#if defined(_LP64) || defined(__ppc64__) || defined(__aarch64__)
typedef long intptr_t;
typedef unsigned long uintptr_t;
#elif defined(_WIN64)
typedef int64_t intptr_t;
typedef uint64_t uintptr_t;
#elif defined(_LP32) || defined(__ppc__) || defined(_WIN32) || defined(__arm__)
typedef int32_t intptr_t;
typedef uint32_t uintptr_t;
#else
#error intptr_t, and uintptr_t undefined
#endif
using size_t = decltype(alignof(int));
#endif
#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunsafe-buffer-usage"
#endif
namespace cityhash::detail {
template<typename T>
struct remove_reference {
using type = T;
};
template<typename T>
struct remove_reference<T&> {
using type = T;
};
template<typename T>
struct remove_reference<T&&> {
using type = T;
};
template<typename T>
using remove_reference_t = typename remove_reference<T>::type;
template<typename T>
constexpr remove_reference_t<T> &&move(T &&t) noexcept {
return static_cast<remove_reference_t<T>&&>(t);
}
template<typename T>
using remove_reference_t = typename remove_reference<T>::type;
template<typename T1, typename T2>
struct pair {
T1 first{};
T2 second{};
constexpr pair() noexcept = default;
constexpr pair(T1 a, T2 b) noexcept: first(detail::move(a)), second(detail::move(b)) {}
};
template<typename T>
constexpr void swap(T &a, T &b) noexcept {
auto temp = detail::move(a);
a = detail::move(b);
b = detail::move(temp);
}
}
namespace cityhash {
using uint128 = cityhash::detail::pair<uint64_t, uint64_t>;
namespace detail {
template<typename T>
[[nodiscard]]
constexpr T byteSwap(T i) noexcept {
if constexpr(sizeof(T) == 1) {
return i;
} else if constexpr(sizeof(T) == 2) {
return static_cast<T>(i << 8) | static_cast<T>(i >> 8);
} else if constexpr(sizeof(T) == 4) {
return ((i >> 24) & 0x000000ff) |
((i >> 8) & 0x0000ff00) |
((i << 8) & 0x00ff0000) |
((i << 24) & 0xff000000);
} else if constexpr(sizeof(T) == 8) {
return ((i >> 56) & 0x00000000000000ff) |
((i >> 40) & 0x000000000000ff00) |
((i >> 24) & 0x0000000000ff0000) |
((i >> 8) & 0x00000000ff000000) |
((i << 8) & 0x000000ff00000000) |
((i << 24) & 0x0000ff0000000000) |
((i << 40) & 0x00ff000000000000) |
((i << 56) & 0xff00000000000000);
}
}
[[nodiscard]]
constexpr uint64_t Uint128Low64(const uint128& x) noexcept { return x.first; }
[[nodiscard]]
constexpr uint64_t Uint128High64(const uint128& x) noexcept { return x.second; }
// Hash 128 input bits down to 64 bits of output.
// This is intended to be a reasonably good hash function.
[[nodiscard]]
constexpr uint64_t Hash128to64(const uint128& x) noexcept {
// Murmur-inspired hashing.
const uint64_t kMul = 0x9ddfea08eb382d69ULL;
uint64_t a = (detail::Uint128Low64(x) ^ detail::Uint128High64(x)) * kMul;
a ^= (a >> 47);
uint64_t b = (detail::Uint128High64(x) ^ a) * kMul;
b ^= (b >> 47);
b *= kMul;
return b;
}
[[nodiscard]]
constexpr uint64_t UNALIGNED_LOAD64(const char *p) noexcept {
uint64_t result{};
result |= static_cast<uint64_t>(p[0]);
result |= static_cast<uint64_t>(p[1]) << 8;
result |= static_cast<uint64_t>(p[2]) << 16;
result |= static_cast<uint64_t>(p[3]) << 24;
result |= static_cast<uint64_t>(p[4]) << 32;
result |= static_cast<uint64_t>(p[5]) << 40;
result |= static_cast<uint64_t>(p[6]) << 48;
result |= static_cast<uint64_t>(p[7]) << 56;
//memcpy(&result, p, sizeof(result));
return result;
}
[[nodiscard]]
constexpr uint32_t UNALIGNED_LOAD32(const char *p) noexcept {
uint32_t result{};
result |= static_cast<uint32_t>(p[0]);
result |= static_cast<uint32_t>(p[1]) << 8;
result |= static_cast<uint32_t>(p[2]) << 16;
result |= static_cast<uint32_t>(p[3]) << 24;
//memcpy(&result, p, sizeof(result));
return result;
}
#ifdef WORDS_BIGENDIAN
#define uint32_in_expected_order(x) (detail::byteSwap<uint32_t>(x))
#define uint64_in_expected_order(x) (detail::byteSwap<uint64_t>(x))
#else
#define uint32_in_expected_order(x) (x)
#define uint64_in_expected_order(x) (x)
#endif
#if !defined(LIKELY)
#if HAVE_BUILTIN_EXPECT
#define LIKELY(x) (__builtin_expect(!!(x), 1))
#else
#define LIKELY(x) (x)
#endif
#endif
[[nodiscard]]
constexpr uint64_t Fetch64(const char *p) noexcept {
return uint64_in_expected_order(UNALIGNED_LOAD64(p));
}
[[nodiscard]]
constexpr uint32_t Fetch32(const char *p) noexcept {
return uint32_in_expected_order(UNALIGNED_LOAD32(p));
}
// Some primes between 2^63 and 2^64 for various uses.
constexpr uint64_t k0 = 0xc3a5c85c97cb3127ULL;
constexpr uint64_t k1 = 0xb492b66fbe98f273ULL;
constexpr uint64_t k2 = 0x9ae16a3b2f90404fULL;
// Magic numbers for 32-bit hashing. Copied from Murmur3.
constexpr uint32_t c1 = 0xcc9e2d51;
constexpr uint32_t c2 = 0x1b873593;
// A 32-bit to 32-bit integer hash copied from Murmur3.
[[nodiscard]]
constexpr uint32_t fmix(uint32_t h) noexcept {
h ^= h >> 16;
h *= 0x85ebca6b;
h ^= h >> 13;
h *= 0xc2b2ae35;
h ^= h >> 16;
return h;
}
[[nodiscard]]
constexpr uint32_t Rotate32(uint32_t val, int shift) noexcept {
// Avoid shifting by 32: doing so yields an undefined result.
return shift == 0 ? val : ((val >> shift) | (val << (32 - shift)));
}
#undef PERMUTE3
#define PERMUTE3(a, b, c) do { detail::swap(a, b); detail::swap(a, c); } while (0)
[[nodiscard]]
constexpr uint32_t Mur(uint32_t a, uint32_t h) noexcept {
// Helper from Murmur3 for combining two 32-bit values.
a *= detail::c1;
a = Rotate32(a, 17);
a *= detail::c2;
h ^= a;
h = Rotate32(h, 19);
return h * 5 + 0xe6546b64;
}
[[nodiscard]]
constexpr uint32_t Hash32Len13to24(const char *s, size_t len) noexcept {
uint32_t a = Fetch32(s - 4 + (len >> 1));
uint32_t b = Fetch32(s + 4);
uint32_t c = Fetch32(s + len - 8);
uint32_t d = Fetch32(s + (len >> 1));
uint32_t e = Fetch32(s);
uint32_t f = Fetch32(s + len - 4);
uint32_t h = static_cast<uint32_t>(len);
return detail::fmix(Mur(f, Mur(e, Mur(d, Mur(c, Mur(b, Mur(a, h)))))));
}
[[nodiscard]]
constexpr uint32_t Hash32Len0to4(const char *s, size_t len) noexcept {
uint32_t b = 0;
uint32_t c = 9;
for (size_t i = 0; i < len; i++) {
auto const v = static_cast<signed char>(s[i]);
b = b * detail::c1 + static_cast<uint32_t>(v);
c ^= b;
}
return detail::fmix(Mur(b, Mur(static_cast<uint32_t>(len), c)));
}
[[nodiscard]]
constexpr uint32_t Hash32Len5to12(const char *s, size_t len) noexcept {
uint32_t a = static_cast<uint32_t>(len), b = a * 5, c = 9, d = b;
a += Fetch32(s);
b += Fetch32(s + len - 4);
c += Fetch32(s + ((len >> 1) & 4));
return detail::fmix(Mur(c, Mur(b, Mur(a, d))));
}
// Bitwise right rotate. Normally this will compile to a single
// instruction, especially if the shift is a manifest constant.
[[nodiscard]]
constexpr uint64_t Rotate(uint64_t val, int shift) noexcept {
// Avoid shifting by 64: doing so yields an undefined result.
return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));
}
[[nodiscard]]
constexpr uint64_t ShiftMix(uint64_t val) noexcept {
return val ^ (val >> 47);
}
[[nodiscard]]
constexpr uint64_t HashLen16(uint64_t u, uint64_t v) noexcept {
return Hash128to64(uint128(u, v));
}
[[nodiscard]]
constexpr uint64_t HashLen16(uint64_t u, uint64_t v, uint64_t mul) noexcept {
// Murmur-inspired hashing.
uint64_t a = (u ^ v) * mul;
a ^= (a >> 47);
uint64_t b = (v ^ a) * mul;
b ^= (b >> 47);
b *= mul;
return b;
}
[[nodiscard]]
constexpr uint64_t HashLen0to16(const char *s, size_t len) noexcept {
if (len >= 8) {
uint64_t mul = detail::k2 + len * 2;
uint64_t a = detail::Fetch64(s) + detail::k2;
uint64_t b = detail::Fetch64(s + len - 8);
uint64_t c = detail::Rotate(b, 37) * mul + a;
uint64_t d = (detail::Rotate(a, 25) + b) * mul;
return HashLen16(c, d, mul);
}
if (len >= 4) {
uint64_t mul = detail::k2 + len * 2;
uint64_t a = Fetch32(s);
return HashLen16(len + (a << 3), Fetch32(s + len - 4), mul);
}
if (len > 0) {
uint8_t a = static_cast<uint8_t>(s[0]);
uint8_t b = static_cast<uint8_t>(s[len >> 1]);
uint8_t c = static_cast<uint8_t>(s[len - 1]);
uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8);
uint32_t z = static_cast<uint32_t>(len) + (static_cast<uint32_t>(c) << 2);
return ShiftMix(y * detail::k2 ^ z * detail::k0) * detail::k2;
}
return detail::k2;
}
// This probably works well for 16-byte strings as well, but it may be overkill
// in that case.
[[nodiscard]]
constexpr uint64_t HashLen17to32(const char *s, size_t len) noexcept {
uint64_t mul = detail::k2 + len * 2;
uint64_t a = detail::Fetch64(s) * detail::k1;
uint64_t b = detail::Fetch64(s + 8);
uint64_t c = detail::Fetch64(s + len - 8) * mul;
uint64_t d = detail::Fetch64(s + len - 16) * detail::k2;
return HashLen16(detail::Rotate(a + b, 43) + detail::Rotate(c, 30) + d,
a + detail::Rotate(b + detail::k2, 18) + c, mul);
}
// Return a 16-byte hash for 48 bytes. Quick and dirty.
// Callers do best to use "random-looking" values for a and b.
[[nodiscard]]
constexpr detail::pair<uint64_t, uint64_t> WeakHashLen32WithSeeds(
uint64_t w, uint64_t x, uint64_t y, uint64_t z, uint64_t a, uint64_t b) noexcept {
a += w;
b = detail::Rotate(b + a + z, 21);
uint64_t c = a;
a += x;
a += y;
b += detail::Rotate(a, 44);
return detail::pair(a + z, b + c);
}
// Return a 16-byte hash for s[0] ... s[31], a, and b. Quick and dirty.
[[nodiscard]]
constexpr detail::pair<uint64_t, uint64_t> WeakHashLen32WithSeeds(
const char* s, uint64_t a, uint64_t b) noexcept {
return WeakHashLen32WithSeeds(detail::Fetch64(s),
detail::Fetch64(s + 8),
detail::Fetch64(s + 16),
detail::Fetch64(s + 24),
a,
b);
}
// Return an 8-byte hash for 33 to 64 bytes.
[[nodiscard]]
constexpr uint64_t HashLen33to64(const char *s, size_t len) noexcept {
uint64_t mul = detail::k2 + len * 2;
uint64_t a = detail::Fetch64(s) * detail::k2;
uint64_t b = detail::Fetch64(s + 8);
uint64_t c = detail::Fetch64(s + len - 24);
uint64_t d = detail::Fetch64(s + len - 32);
uint64_t e = detail::Fetch64(s + 16) * detail::k2;
uint64_t f = detail::Fetch64(s + 24) * 9;
uint64_t g = detail::Fetch64(s + len - 8);
uint64_t h = detail::Fetch64(s + len - 16) * mul;
uint64_t u = detail::Rotate(a + g, 43) + (detail::Rotate(b, 30) + c) * 9;
uint64_t v = ((a + g) ^ d) + f + 1;
uint64_t w = detail::byteSwap((u + v) * mul) + h;
uint64_t x = detail::Rotate(e + f, 42) + c;
uint64_t y = (detail::byteSwap((v + w) * mul) + g) * mul;
uint64_t z = e + f + c;
a = detail::byteSwap((x + z) * mul + y) + b;
b = ShiftMix((z + a) * mul + d + h) * mul;
return b + x;
}
// A subroutine for CityHash128(). Returns a decent 128-bit hash for strings
// of any length representable in signed long. Based on City and Murmur.
[[nodiscard]]
constexpr uint128 CityMurmur(const char *s, size_t len, uint128 seed) noexcept {
uint64_t a = detail::Uint128Low64(seed);
uint64_t b = detail::Uint128High64(seed);
uint64_t c = 0;
uint64_t d = 0;
if (len <= 16) {
a = ShiftMix(a * detail::k1) * detail::k1;
c = b * detail::k1 + HashLen0to16(s, len);
d = ShiftMix(a + (len >= 8 ? detail::Fetch64(s) : c));
} else {
c = HashLen16(detail::Fetch64(s + len - 8) + detail::k1, a);
d = HashLen16(b + len, c + detail::Fetch64(s + len - 16));
a += d;
// len > 16 here, so do...while is safe
do {
a ^= ShiftMix(detail::Fetch64(s) * detail::k1) * detail::k1;
a *= detail::k1;
b ^= a;
c ^= ShiftMix(detail::Fetch64(s + 8) * detail::k1) * detail::k1;
c *= detail::k1;
d ^= c;
s += 16;
len -= 16;
} while (len > 16);
}
a = HashLen16(a, c);
b = HashLen16(d, b);
return uint128(a ^ b, HashLen16(b, a));
}
}
[[nodiscard]]
constexpr uint32_t CityHash32(const char *s, size_t len) noexcept {
if (len <= 24) {
return len <= 12 ?
(len <= 4 ? detail::Hash32Len0to4(s, len) : detail::Hash32Len5to12(s, len)) :
detail::Hash32Len13to24(s, len);
}
// len > 24
uint32_t h = static_cast<uint32_t>(len), g = detail::c1 * h, f = g;
uint32_t a0 = detail::Rotate32(detail::Fetch32(s + len - 4) * detail::c1, 17) * detail::c2;
uint32_t a1 = detail::Rotate32(detail::Fetch32(s + len - 8) * detail::c1, 17) * detail::c2;
uint32_t a2 = detail::Rotate32(detail::Fetch32(s + len - 16) * detail::c1, 17) * detail::c2;
uint32_t a3 = detail::Rotate32(detail::Fetch32(s + len - 12) * detail::c1, 17) * detail::c2;
uint32_t a4 = detail::Rotate32(detail::Fetch32(s + len - 20) * detail::c1, 17) * detail::c2;
h ^= a0;
h = detail::Rotate32(h, 19);
h = h * 5 + 0xe6546b64;
h ^= a2;
h = detail::Rotate32(h, 19);
h = h * 5 + 0xe6546b64;
g ^= a1;
g = detail::Rotate32(g, 19);
g = g * 5 + 0xe6546b64;
g ^= a3;
g = detail::Rotate32(g, 19);
g = g * 5 + 0xe6546b64;
f += a4;
f = detail::Rotate32(f, 19);
f = f * 5 + 0xe6546b64;
size_t iters = (len - 1) / 20;
do {
uint32_t a0 = detail::Rotate32(detail::Fetch32(s) * detail::c1, 17) * detail::c2;
uint32_t a1 = detail::Fetch32(s + 4);
uint32_t a2 = detail::Rotate32(detail::Fetch32(s + 8) * detail::c1, 17) * detail::c2;
uint32_t a3 = detail::Rotate32(detail::Fetch32(s + 12) * detail::c1, 17) * detail::c2;
uint32_t a4 = detail::Fetch32(s + 16);
h ^= a0;
h = detail::Rotate32(h, 18);
h = h * 5 + 0xe6546b64;
f += a1;
f = detail::Rotate32(f, 19);
f = f * detail::c1;
g += a2;
g = detail::Rotate32(g, 18);
g = g * 5 + 0xe6546b64;
h ^= a3 + a1;
h = detail::Rotate32(h, 19);
h = h * 5 + 0xe6546b64;
g ^= a4;
g = detail::byteSwap(g) * 5;
h += a4 * 5;
h = detail::byteSwap(h);
f += a0;
PERMUTE3(f, h, g);
s += 20;
} while (--iters != 0);
g = detail::Rotate32(g, 11) * detail::c1;
g = detail::Rotate32(g, 17) * detail::c1;
f = detail::Rotate32(f, 11) * detail::c1;
f = detail::Rotate32(f, 17) * detail::c1;
h = detail::Rotate32(h + g, 19);
h = h * 5 + 0xe6546b64;
h = detail::Rotate32(h, 17) * detail::c1;
h = detail::Rotate32(h + f, 19);
h = h * 5 + 0xe6546b64;
h = detail::Rotate32(h, 17) * detail::c1;
return h;
}
[[nodiscard]]
constexpr uint64_t CityHash64(const char *s, size_t len) noexcept {
if (len <= 32) {
if (len <= 16) {
return detail::HashLen0to16(s, len);
} else {
return detail::HashLen17to32(s, len);
}
} else if (len <= 64) {
return detail::HashLen33to64(s, len);
}
// For strings over 64 bytes we hash the end first, and then as we
// loop we keep 56 bytes of state: v, w, x, y, and z.
uint64_t x = detail::Fetch64(s + len - 40);
uint64_t y = detail::Fetch64(s + len - 16) + detail::Fetch64(s + len - 56);
uint64_t z = detail::HashLen16(detail::Fetch64(s + len - 48) + len, detail::Fetch64(s + len - 24));
detail::pair<uint64_t, uint64_t> v = detail::WeakHashLen32WithSeeds(s + len - 64, len, z);
detail::pair<uint64_t, uint64_t> w = detail::WeakHashLen32WithSeeds(s + len - 32, y + detail::k1, x);
x = x * detail::k1 + detail::Fetch64(s);
// Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
len = (len - 1) & ~static_cast<size_t>(63);
do {
x = detail::Rotate(x + y + v.first + detail::Fetch64(s + 8), 37) * detail::k1;
y = detail::Rotate(y + v.second + detail::Fetch64(s + 48), 42) * detail::k1;
x ^= w.second;
y += v.first + detail::Fetch64(s + 40);
z = detail::Rotate(z + w.first, 33) * detail::k1;
v = detail::WeakHashLen32WithSeeds(s, v.second * detail::k1, x + w.first);
w = detail::WeakHashLen32WithSeeds(s + 32, z + w.second, y + detail::Fetch64(s + 16));
detail::swap(z, x);
s += 64;
len -= 64;
} while (len != 0);
return detail::HashLen16(detail::HashLen16(v.first, w.first) + detail::ShiftMix(y) * detail::k1 + z,
detail::HashLen16(v.second, w.second) + x);
}
[[nodiscard]]
constexpr uint64_t CityHash64WithSeeds(const char *s, size_t len,
uint64_t seed0, uint64_t seed1) noexcept {
return detail::HashLen16(CityHash64(s, len) - seed0, seed1);
}
[[nodiscard]]
constexpr uint64_t CityHash64WithSeed(const char *s, size_t len, uint64_t seed) noexcept {
return CityHash64WithSeeds(s, len, detail::k2, seed);
}
[[nodiscard]]
constexpr uint128 CityHash128WithSeed(const char *s, size_t len, uint128 seed) noexcept {
if (len < 128) {
return detail::CityMurmur(s, len, seed);
}
// We expect len >= 128 to be the common case. Keep 56 bytes of state:
// v, w, x, y, and z.
detail::pair<uint64_t, uint64_t> v, w;
uint64_t x = detail::Uint128Low64(seed);
uint64_t y = detail::Uint128High64(seed);
uint64_t z = len * detail::k1;
v.first = detail::Rotate(y ^ detail::k1, 49) * detail::k1 + detail::Fetch64(s);
v.second = detail::Rotate(v.first, 42) * detail::k1 + detail::Fetch64(s + 8);
w.first = detail::Rotate(y + z, 35) * detail::k1 + x;
w.second = detail::Rotate(x + detail::Fetch64(s + 88), 53) * detail::k1;
// This is the same inner loop as CityHash64(), manually unrolled.
do {
x = detail::Rotate(x + y + v.first + detail::Fetch64(s + 8), 37) * detail::k1;
y = detail::Rotate(y + v.second + detail::Fetch64(s + 48), 42) * detail::k1;
x ^= w.second;
y += v.first + detail::Fetch64(s + 40);
z = detail::Rotate(z + w.first, 33) * detail::k1;
v = detail::WeakHashLen32WithSeeds(s, v.second * detail::k1, x + w.first);
w = detail::WeakHashLen32WithSeeds(s + 32, z + w.second, y + detail::Fetch64(s + 16));
detail::swap(z, x);
s += 64;
x = detail::Rotate(x + y + v.first + detail::Fetch64(s + 8), 37) * detail::k1;
y = detail::Rotate(y + v.second + detail::Fetch64(s + 48), 42) * detail::k1;
x ^= w.second;
y += v.first + detail::Fetch64(s + 40);
z = detail::Rotate(z + w.first, 33) * detail::k1;
v = detail::WeakHashLen32WithSeeds(s, v.second * detail::k1, x + w.first);
w = detail::WeakHashLen32WithSeeds(s + 32, z + w.second, y + detail::Fetch64(s + 16));
detail::swap(z, x);
s += 64;
len -= 128;
} while (LIKELY(len >= 128));
x += detail::Rotate(v.first + z, 49) * detail::k0;
y = y * detail::k0 + detail::Rotate(w.second, 37);
z = z * detail::k0 + detail::Rotate(w.first, 27);
w.first *= 9;
v.first *= detail::k0;
// If 0 < len < 128, hash up to 4 chunks of 32 bytes each from the end of s.
for (size_t tail_done = 0; tail_done < len; ) {
tail_done += 32;
y = detail::Rotate(x + y, 42) * detail::k0 + v.second;
w.first += detail::Fetch64(s + len - tail_done + 16);
x = x * detail::k0 + w.first;
z += w.second + detail::Fetch64(s + len - tail_done);
w.second += v.first;
v = detail::WeakHashLen32WithSeeds(s + len - tail_done, v.first + z, v.second);
v.first *= detail::k0;
}
// At this point our 56 bytes of state should contain more than
// enough information for a strong 128-bit hash. We use two
// different 56-byte-to-8-byte hashes to get a 16-byte final result.
x = detail::HashLen16(x, v.first);
y = detail::HashLen16(y + z, w.first);
return uint128(detail::HashLen16(x + v.second, w.second) + y,
detail::HashLen16(x + w.second, y + v.second));
}
[[nodiscard]]
constexpr uint128 CityHash128(const char *s, size_t len) noexcept {
return len >= 16 ?
CityHash128WithSeed(s + 16, len - 16,
uint128(detail::Fetch64(s), detail::Fetch64(s + 8) + detail::k0)) :
CityHash128WithSeed(s, len, uint128(detail::k0, detail::k1));
}
}
#ifdef __clang__
#pragma clang diagnostic pop
#endif
#endif // CITY_HASH_H_
Reference in New Issue View Git Blame Copy Permalink