src/support/city.c

/* 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 "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)						\
	do {								\
		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							\
	} while (0)

		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