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contrib/mg/mi_vector_hash.c

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/* $NetBSD: mi_vector_hash.c,v 1.1 2013/12/11 01:24:08 joerg Exp $ */
/*-
* Copyright (c) 2009 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Joerg Sonnenberger.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* See http://burtleburtle.net/bob/hash/doobs.html for the full description
* and the original version of the code. This version differs by exposing
* the full internal state and avoiding byte operations in the inner loop
* if the key is aligned correctly.
*/
#include <sys/cdefs.h>
#include <stdint.h>
#include <stdlib.h>
#define mix(a, b, c) do { \
a -= b; a -= c; a ^= (c >> 13); \
b -= c; b -= a; b ^= (a << 8); \
c -= a; c -= b; c ^= (b >> 13); \
a -= b; a -= c; a ^= (c >> 12); \
b -= c; b -= a; b ^= (a << 16); \
c -= a; c -= b; c ^= (b >> 5); \
a -= b; a -= c; a ^= (c >> 3); \
b -= c; b -= a; b ^= (a << 10); \
c -= a; c -= b; c ^= (b >> 15); \
} while (/* CONSTCOND */0)
#define FIXED_SEED 0x9e3779b9 /* Golden ratio, arbitrary constant */
/* From NetBSD sys/external/bsd/libnv/dist/nv_compat.h */
static uint32_t
le32dec(const void *buf)
{
uint8_t const *p = (uint8_t const *) buf;
return (((unsigned) p[3] << 24) | (p[2] << 16) | (p[1] << 8) | p[0]);
}
void
mi_vector_hash(const void * __restrict key, size_t len, uint32_t seed,
uint32_t hashes[3])
{
static const uint32_t mask[4] = {
0x000000ff, 0x0000ffff, 0x00ffffff, 0xffffffff
};
uint32_t orig_len, a, b, c;
const uint8_t *k;
orig_len = (uint32_t)len;
a = b = FIXED_SEED;
c = seed;
if ((uintptr_t)key & 3) {
k = key;
while (len >= 12) {
a += le32dec(k);
b += le32dec(k + 4);
c += le32dec(k + 8);
mix(a, b, c);
k += 12;
len -= 12;
}
c += orig_len;
if (len > 8) {
switch (len) {
case 11:
c += (uint32_t)k[10] << 24;
/* FALLTHROUGH */
case 10:
c += (uint32_t)k[9] << 16;
/* FALLTHROUGH */
case 9:
c += (uint32_t)k[8] << 8;
/* FALLTHROUGH */
}
b += le32dec(k + 4);
a += le32dec(k);
} else if (len > 4) {
switch (len) {
case 8:
b += (uint32_t)k[7] << 24;
/* FALLTHROUGH */
case 7:
b += (uint32_t)k[6] << 16;
/* FALLTHROUGH */
case 6:
b += (uint32_t)k[5] << 8;
/* FALLTHROUGH */
case 5:
b += k[4];
/* FALLTHROUGH */
}
a += le32dec(k);
} else if (len) {
switch (len) {
case 4:
a += (uint32_t)k[3] << 24;
/* FALLTHROUGH */
case 3:
a += (uint32_t)k[2] << 16;
/* FALLTHROUGH */
case 2:
a += (uint32_t)k[1] << 8;
/* FALLTHROUGH */
case 1:
a += k[0];
/* FALLTHROUGH */
}
}
} else {
const uint32_t *key32 = key;
while (len >= 12) {
a += le32toh(key32[0]);
b += le32toh(key32[1]);
c += le32toh(key32[2]);
mix(a, b, c);
key32 += 3;
len -= 12;
}
c += orig_len;
if (len > 8) {
c += (le32toh(key32[2]) & mask[len - 9]) << 8;
b += le32toh(key32[1]);
a += le32toh(key32[0]);
} else if (len > 4) {
b += le32toh(key32[1]) & mask[len - 5];
a += le32toh(key32[0]);
} else if (len)
a += le32toh(key32[0]) & mask[len - 1];
}
mix(a, b, c);
hashes[0] = a;
hashes[1] = b;
hashes[2] = c;
}