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/* city.c - cityhash-c
* CityHash on C
* Copyright (c) 2011-2012, Alexander Nusov
*
* - original copyright notice -
* 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
*
* This file provides CityHash64() and related functions.
*
* It's probably possible to create even faster hash functions by
* writing a program that systematically explores some of the space of
* possible hash functions, by using SIMD instructions, or by
* compromising on hash quality.
*/
#include <string.h>
#include <misc/city.h>
static uint64 UNALIGNED_LOAD64(const char *p)
{
uint64 result;
memcpy(&result, p, sizeof(result));
return result;
}
static uint32 UNALIGNED_LOAD32(const char *p)
{
uint32 result;
memcpy(&result, p, sizeof(result));
return result;
}
#if !defined(WORDS_BIGENDIAN)
#define uint32_in_expected_order(x) (x)
#define uint64_in_expected_order(x) (x)
#else
#ifdef _MSC_VER
#include <stdlib.h>
#define bswap_32(x) _byteswap_ulong(x)
#define bswap_64(x) _byteswap_uint64(x)
#elif defined(__APPLE__)
/* Mac OS X / Darwin features */
#include <libkern/OSByteOrder.h>
#define bswap_32(x) OSSwapInt32(x)
#define bswap_64(x) OSSwapInt64(x)
#else
#include <byteswap.h>
#endif
#define uint32_in_expected_order(x) (bswap_32(x))
#define uint64_in_expected_order(x) (bswap_64(x))
#endif /* WORDS_BIGENDIAN */
#if !defined(LIKELY)
#if HAVE_BUILTIN_EXPECT
#define LIKELY(x) (__builtin_expect(!!(x), 1))
#else
#define LIKELY(x) (x)
#endif
#endif
static uint64 Fetch64(const char *p)
{
return uint64_in_expected_order(UNALIGNED_LOAD64(p));
}
static uint32 Fetch32(const char *p)
{
return uint32_in_expected_order(UNALIGNED_LOAD32(p));
}
/* Some primes between 2^63 and 2^64 for various uses. */
static const uint64 k0 = 0xc3a5c85c97cb3127ULL;
static const uint64 k1 = 0xb492b66fbe98f273ULL;
static const uint64 k2 = 0x9ae16a3b2f90404fULL;
static const uint64 k3 = 0xc949d7c7509e6557ULL;
/* Hash 128 input bits down to 64 bits of output.
* This is intended to be a reasonably good hash function.
*/
static inline uint64 Hash128to64(const uint128 x)
{
/* Murmur-inspired hashing. */
const uint64 kMul = 0x9ddfea08eb382d69ULL;
uint64 a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;
a ^= (a >> 47);
uint64 b = (Uint128High64(x) ^ a) * kMul;
b ^= (b >> 47);
b *= kMul;
return b;
}
/* Bitwise right rotate. Normally this will compile to a single
* instruction, especially if the shift is a manifest constant. */
static uint64 Rotate(uint64 val, int shift)
{
/* Avoid shifting by 64: doing so yields an undefined result. */
return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));
}
/* Equivalent to Rotate(), but requires the second arg to be non-zero.
* On x86-64, and probably others, it's possible for this to compile
* to a single instruction if both args are already in registers. */
static uint64 RotateByAtLeast1(uint64 val, int shift)
{
return (val >> shift) | (val << (64 - shift));
}
static uint64 ShiftMix(uint64 val)
{
return val ^ (val >> 47);
}
static uint64 HashLen16(uint64 u, uint64 v)
{
uint128 result;
result.first = u;
result.second = v;
return Hash128to64(result);
}
static uint64 HashLen0to16(const char *s, size_t len)
{
if (len > 8) {
uint64 a = Fetch64(s);
uint64 b = Fetch64(s + len - 8);
return HashLen16(a, RotateByAtLeast1(b + len, len)) ^ b;
}
if (len >= 4) {
uint64 a = Fetch32(s);
return HashLen16(len + (a << 3), Fetch32(s + len - 4));
}
if (len > 0) {
uint8 a = s[0];
uint8 b = s[len >> 1];
uint8 c = s[len - 1];
uint32 y = (uint32) (a) + ((uint32) (b) << 8);
uint32 z = len + ((uint32) (c) << 2);
return ShiftMix(y * k2 ^ z * k3) * k2;
}
return k2;
}
/* This probably works well for 16-byte strings as well, but it may be overkill
* in that case. */
static uint64 HashLen17to32(const char *s, size_t len)
{
uint64 a = Fetch64(s) * k1;
uint64 b = Fetch64(s + 8);
uint64 c = Fetch64(s + len - 8) * k2;
uint64 d = Fetch64(s + len - 16) * k0;
return HashLen16(Rotate(a - b, 43) + Rotate(c, 30) + d,
a + Rotate(b ^ k3, 20) - c + len);
}
/* Return a 16-byte hash for 48 bytes. Quick and dirty.
Callers do best to use "random-looking" values for a and b.
static pair<uint64, uint64> WeakHashLen32WithSeeds(
*/
uint128 WeakHashLen32WithSeeds6(uint64 w, uint64 x, uint64 y, uint64 z,
uint64 a, uint64 b)
{
a += w;
b = Rotate(b + a + z, 21);
uint64 c = a;
a += x;
a += y;
b += Rotate(a, 44);
uint128 result;
result.first = (uint64) (a + z);
result.second = (uint64) (b + c);
return result;
}
/* Return a 16-byte hash for s[0] ... s[31], a, and b. Quick and dirty.
* static pair<uint64, uint64> WeakHashLen32WithSeeds( */
uint128 WeakHashLen32WithSeeds(const char *s, uint64 a, uint64 b)
{
return WeakHashLen32WithSeeds6(Fetch64(s), Fetch64(s + 8),
Fetch64(s + 16), Fetch64(s + 24), a, b);
}
/* Return an 8-byte hash for 33 to 64 bytes. */
static uint64 HashLen33to64(const char *s, size_t len)
{
uint64 z = Fetch64(s + 24);
uint64 a = Fetch64(s) + (len + Fetch64(s + len - 16)) * k0;
uint64 b = Rotate(a + z, 52);
uint64 c = Rotate(a, 37);
a += Fetch64(s + 8);
c += Rotate(a, 7);
a += Fetch64(s + 16);
uint64 vf = a + z;
uint64 vs = b + Rotate(a, 31) + c;
a = Fetch64(s + 16) + Fetch64(s + len - 32);
z = Fetch64(s + len - 8);
b = Rotate(a + z, 52);
c = Rotate(a, 37);
a += Fetch64(s + len - 24);
c += Rotate(a, 7);
a += Fetch64(s + len - 16);
uint64 wf = a + z;
uint64 ws = b + Rotate(a, 31) + c;
uint64 r = ShiftMix((vf + ws) * k2 + (wf + vs) * k0);
return ShiftMix(r * k0 + vs) * k2;
}
uint64 CityHash64(const char *s, size_t len)
{
if (len <= 32) {
if (len <= 16)
return HashLen0to16(s, len);
else
return HashLen17to32(s, len);
} else if (len <= 64)
return 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 x = Fetch64(s + len - 40);
uint64 y = Fetch64(s + len - 16) + Fetch64(s + len - 56);
uint64 z =
HashLen16(Fetch64(s + len - 48) + len, Fetch64(s + len - 24));
uint64 temp;
uint128 v = WeakHashLen32WithSeeds(s + len - 64, len, z);
uint128 w = WeakHashLen32WithSeeds(s + len - 32, y + k1, x);
x = x * k1 + Fetch64(s);
/* Decrease len to the nearest multiple of 64, and operate on 64-byte
* chunks. */
len = (len - 1) & ~(size_t) (63);
do {
x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1;
y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1;
x ^= w.second;
y += v.first + Fetch64(s + 40);
z = Rotate(z + w.first, 33) * k1;
v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);
w = WeakHashLen32WithSeeds(s + 32, z + w.second,
y + Fetch64(s + 16));
temp = z;
z = x;
x = temp;
s += 64;
len -= 64;
} while (len != 0);
return HashLen16(HashLen16(v.first, w.first) + ShiftMix(y) * k1 + z,
HashLen16(v.second, w.second) + x);
}
uint64 CityHash64WithSeed(const char *s, size_t len, uint64 seed)
{
return CityHash64WithSeeds(s, len, k2, seed);
}
uint64 CityHash64WithSeeds(const char *s, size_t len, uint64 seed0,
uint64 seed1)
{
return HashLen16(CityHash64(s, len) - seed0, seed1);
}
/* A subroutine for CityHash128(). Returns a decent 128-bit hash for strings
* of any length representable in signed long. Based on City and Murmur. */
static uint128 CityMurmur(const char *s, size_t len, uint128 seed)
{
uint64 a = Uint128Low64(seed);
uint64 b = Uint128High64(seed);
uint64 c = 0;
uint64 d = 0;
signed long l = len - 16;
if (l <= 0) { /* len <= 16 */
a = ShiftMix(a * k1) * k1;
c = b * k1 + HashLen0to16(s, len);
d = ShiftMix(a + (len >= 8 ? Fetch64(s) : c));
} else { /* len > 16 */
c = HashLen16(Fetch64(s + len - 8) + k1, a);
d = HashLen16(b + len, c + Fetch64(s + len - 16));
a += d;
do {
a ^= ShiftMix(Fetch64(s) * k1) * k1;
a *= k1;
b ^= a;
c ^= ShiftMix(Fetch64(s + 8) * k1) * k1;
c *= k1;
d ^= c;
s += 16;
l -= 16;
} while (l > 0);
}
a = HashLen16(a, c);
b = HashLen16(d, b);
uint128 result;
result.first = (uint64) (a ^ b);
result.second = (uint64) (HashLen16(b, a));
return result;
}
uint128 CityHash128WithSeed(const char *s, size_t len, uint128 seed)
{
if (len < 128)
return CityMurmur(s, len, seed);
/* We expect len >= 128 to be the common case. Keep 56 bytes of state:
* v, w, x, y, and z. */
uint128 v, w;
uint64 x = Uint128Low64(seed);
uint64 y = Uint128High64(seed);
uint64 z = len * k1;
uint64 temp;
v.first = Rotate(y ^ k1, 49) * k1 + Fetch64(s);
v.second = Rotate(v.first, 42) * k1 + Fetch64(s + 8);
w.first = Rotate(y + z, 35) * k1 + x;
w.second = Rotate(x + Fetch64(s + 88), 53) * k1;
/* This is the same inner loop as CityHash64(), manually unrolled. */
do {
x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1;
y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1;
x ^= w.second;
y += v.first + Fetch64(s + 40);
z = Rotate(z + w.first, 33) * k1;
v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);
w = WeakHashLen32WithSeeds(s + 32, z + w.second,
y + Fetch64(s + 16));
temp = z;
z = x;
x = temp;
s += 64;
x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1;
y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1;
x ^= w.second;
y += v.first + Fetch64(s + 40);
z = Rotate(z + w.first, 33) * k1;
v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);
w = WeakHashLen32WithSeeds(s + 32, z + w.second,
y + Fetch64(s + 16));
temp = z;
z = x;
x = temp;
s += 64;
len -= 128;
} while (LIKELY(len >= 128));
x += Rotate(v.first + z, 49) * k0;
z += Rotate(w.first, 37) * k0;
/* If 0 < len < 128, hash up to 4 chunks of 32 bytes each from the end
* of s. */
size_t tail_done;
for (tail_done = 0; tail_done < len;) {
tail_done += 32;
y = Rotate(x + y, 42) * k0 + v.second;
w.first += Fetch64(s + len - tail_done + 16);
x = x * k0 + w.first;
z += w.second + Fetch64(s + len - tail_done);
w.second += v.first;
v = WeakHashLen32WithSeeds(s + len - tail_done, v.first + z,
v.second);
}
/* 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 = HashLen16(x, v.first);
y = HashLen16(y + z, w.first);
uint128 result;
result.first = (uint64) (HashLen16(x + v.second, w.second) + y);
result.second = (uint64) HashLen16(x + w.second, y + v.second);
return result;
}
uint128 CityHash128(const char *s, size_t len)
{
uint128 r;
if (len >= 16) {
r.first = (uint64) (Fetch64(s) ^ k3);
r.second = (uint64) (Fetch64(s + 8));
return CityHash128WithSeed(s + 16, len - 16, r);
} else if (len >= 8) {
r.first = (uint64) (Fetch64(s) ^ (len * k0));
r.second = (uint64) (Fetch64(s + len - 8) ^ k1);
return CityHash128WithSeed(NULL, 0, r);
} else {
r.first = (uint64) k0;
r.second = (uint64) k1;
return CityHash128WithSeed(s, len, r);
}
}
#ifdef __SSE4_2__
#include "citycrc.h"
#include <nmmintrin.h>
/* Requires len >= 240. */
static void CityHashCrc256Long(const char *s, size_t len, uint32 seed,
uint64 * result)
{
uint64 a = Fetch64(s + 56) + k0;
uint64 b = Fetch64(s + 96) + k0;
uint64 c = result[0] = HashLen16(b, len);
uint64 d = result[1] = Fetch64(s + 120) * k0 + len;
uint64 e = Fetch64(s + 184) + seed;
uint64 f = seed;
uint64 g = 0;
uint64 h = 0;
uint64 i = 0;
uint64 j = 0;
uint64 t = c + d;
/* 240 bytes of input per iter. */
size_t iters = len / 240;
len -= iters * 240;
do {
#define CHUNK(multiplier, z) \
{ \
uint64 old_a = a; \
a = Rotate(b, 41 ^ z) * multiplier + Fetch64(s); \
b = Rotate(c, 27 ^ z) * multiplier + Fetch64(s + 8); \
c = Rotate(d, 41 ^ z) * multiplier + Fetch64(s + 16); \
d = Rotate(e, 33 ^ z) * multiplier + Fetch64(s + 24); \
e = Rotate(t, 25 ^ z) * multiplier + Fetch64(s + 32); \
t = old_a; \
} \
f = _mm_crc32_u64(f, a); \
g = _mm_crc32_u64(g, b); \
h = _mm_crc32_u64(h, c); \
i = _mm_crc32_u64(i, d); \
j = _mm_crc32_u64(j, e); \
s += 40
CHUNK(1, 1);
CHUNK(k0, 0);
CHUNK(1, 1);
CHUNK(k0, 0);
CHUNK(1, 1);
CHUNK(k0, 0);
} while (--iters > 0);
while (len >= 40) {
CHUNK(k0, 0);
len -= 40;
}
if (len > 0) {
s = s + len - 40;
CHUNK(k0, 0);
}
j += i << 32;
a = HashLen16(a, j);
h += g << 32;
b += h;
c = HashLen16(c, f) + i;
d = HashLen16(d, e + result[0]);
j += e;
i += HashLen16(h, t);
e = HashLen16(a, d) + j;
f = HashLen16(b, c) + a;
g = HashLen16(j, i) + c;
result[0] = e + f + g + h;
a = ShiftMix((a + g) * k0) * k0 + b;
result[1] += a + result[0];
a = ShiftMix(a * k0) * k0 + c;
result[2] = a + result[1];
a = ShiftMix((a + e) * k0) * k0;
result[3] = a + result[2];
}
/* Requires len < 240. */
static void CityHashCrc256Short(const char *s, size_t len, uint64 *result)
{
char buf[240];
memcpy(buf, s, len);
memset(buf + len, 0, 240 - len);
CityHashCrc256Long(buf, 240, ~(uint32) (len), result);
}
void CityHashCrc256(const char *s, size_t len, uint64 *result)
{
if (LIKELY(len >= 240))
CityHashCrc256Long(s, len, 0, result);
else
CityHashCrc256Short(s, len, result);
}
uint128 CityHashCrc128WithSeed(const char *s, size_t len, uint128 seed)
{
if (len <= 900) {
return CityHash128WithSeed(s, len, seed);
} else {
uint64 result[4];
CityHashCrc256(s, len, result);
uint64 u = Uint128High64(seed) + result[0];
uint64 v = Uint128Low64(seed) + result[1];
uint128 crc;
crc.first = (uint64) (HashLen16(u, v + result[2]));
crc.second =
(uint64) (HashLen16(Rotate(v, 32), u * k0 + result[3]));
return crc;
}
}
uint128 CityHashCrc128(const char *s, size_t len)
{
if (len <= 900) {
return CityHash128(s, len);
} else {
uint64 result[4];
CityHashCrc256(s, len, result);
uint128 crc;
crc.first = (uint64) result[2];
crc.second = (uint64) result[3];
return crc;
}
}
#endif