lib/libc/stdlib/mi_vector_hash.c

   1 /*      $NetBSD: mi_vector_hash.c,v 1.3 2010/03/19 18:11:30 joerg Exp $ */
   2 /*-
   3  * Copyright (c) 2009 The NetBSD Foundation, Inc.
   4  * All rights reserved.
   5  *
   6  * This code is derived from software contributed to The NetBSD Foundation
   7  * by Joerg Sonnenberger.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  *
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in
  17  *    the documentation and/or other materials provided with the
  18  *    distribution.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  24  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  25  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  27  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  30  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 /*
  35  * See http://burtleburtle.net/bob/hash/doobs.html for the full description
  36  * and the original version of the code.  This version differs by exposing
  37  * the full internal state and avoiding byte operations in the inner loop
  38  * if the key is aligned correctly.
  39  */
  40
  41 #if HAVE_NBTOOL_CONFIG_H
  42 #include "nbtool_config.h"
  43 #endif
  44
  45 #include <sys/cdefs.h>
  46 __RCSID("$NetBSD: mi_vector_hash.c,v 1.3 2010/03/19 18:11:30 joerg Exp $");
  47
  48 #include "namespace.h"
  49
  50 #include <sys/endian.h>
  51 #include <stdint.h>
  52 #include <stdlib.h>
  53
  54 #define mix(a, b, c) do {               \
  55         a -= b; a -= c; a ^= (c >> 13); \
  56         b -= c; b -= a; b ^= (a << 8);  \
  57         c -= a; c -= b; c ^= (b >> 13); \
  58         a -= b; a -= c; a ^= (c >> 12); \
  59         b -= c; b -= a; b ^= (a << 16); \
  60         c -= a; c -= b; c ^= (b >> 5);  \
  61         a -= b; a -= c; a ^= (c >> 3);  \
  62         b -= c; b -= a; b ^= (a << 10); \
  63         c -= a; c -= b; c ^= (b >> 15); \
  64 } while (/* CONSTCOND */0)
  65
  66 #define FIXED_SEED      0x9e3779b9      /* Golden ratio, arbitrary constant */
  67
  68 #ifdef __weak_alias
  69 __weak_alias(mi_vector_hash, _mi_vector_hash)
  70 #endif
  71
  72 void
  73 mi_vector_hash(const void * __restrict key, size_t len, uint32_t seed,
  74     uint32_t hashes[3])
  75 {
  76         static const uint32_t mask[4] = {
  77                 0x000000ff, 0x0000ffff, 0x00ffffff, 0xffffffff
  78         };
  79         uint32_t orig_len, a, b, c;
  80         const uint8_t *k;
  81
  82         orig_len = (uint32_t)len;
  83
  84         a = b = FIXED_SEED;
  85         c = seed;
  86
  87         if ((uintptr_t)key & 3) {
  88                 k = key;
  89                 while (len >= 12) {
  90                         a += le32dec(k);
  91                         b += le32dec(k + 4);
  92                         c += le32dec(k + 8);
  93                         mix(a, b, c);
  94                         k += 12;
  95                         len -= 12;
  96                 }
  97                 c += orig_len;
  98
  99                 if (len > 8) {
 100                         switch (len) {
 101                         case 11:
 102                                 c += (uint32_t)k[10] << 24;
 103                                 /* FALLTHROUGH */
 104                         case 10:
 105                                 c += (uint32_t)k[9] << 16;
 106                                 /* FALLTHROUGH */
 107                         case 9:
 108                                 c += (uint32_t)k[8] << 8;
 109                                 /* FALLTHROUGH */
 110                         }
 111                         b += le32dec(k + 4);
 112                         a += le32dec(k);
 113                 } else if (len > 4) {
 114                         switch (len) {
 115                         case 8:
 116                                 b += (uint32_t)k[7] << 24;
 117                                 /* FALLTHROUGH */
 118                         case 7:
 119                                 b += (uint32_t)k[6] << 16;
 120                                 /* FALLTHROUGH */
 121                         case 6:
 122                                 b += (uint32_t)k[5] << 8;
 123                                 /* FALLTHROUGH */
 124                         case 5:
 125                                 b += k[4];
 126                                 /* FALLTHROUGH */
 127                         }
 128                         a += le32dec(k);
 129                 } else if (len) {
 130                         switch (len) {
 131                         case 4:
 132                                 a += (uint32_t)k[3] << 24;
 133                                 /* FALLTHROUGH */
 134                         case 3:
 135                                 a += (uint32_t)k[2] << 16;
 136                                 /* FALLTHROUGH */
 137                         case 2:
 138                                 a += (uint32_t)k[1] << 8;
 139                                 /* FALLTHROUGH */
 140                         case 1:
 141                                 a += k[0];
 142                                 /* FALLTHROUGH */
 143                         }
 144                 }
 145         } else {
 146                 const uint32_t *key32 = key;
 147                 while (len >= 12) {
 148                         a += le32toh(key32[0]);
 149                         b += le32toh(key32[1]);
 150                         c += le32toh(key32[2]);
 151                         mix(a, b, c);
 152                         key32 += 3;
 153                         len -= 12;
 154                 }
 155                 c += orig_len;
 156
 157                 if (len > 8) {
 158                         c += (le32toh(key32[2]) & mask[len - 9]) << 8;
 159                         b += le32toh(key32[1]);
 160                         a += le32toh(key32[0]);
 161                 } else if (len > 4) {
 162                         b += le32toh(key32[1]) & mask[len - 5];
 163                         a += le32toh(key32[0]);
 164                 } else if (len)
 165                         a += le32toh(key32[0]) & mask[len - 1];
 166         }
 167         mix(a, b, c);
 168         hashes[0] = a;
 169         hashes[1] = b;
 170         hashes[2] = c;
 171 }