lib/libc/stdlib/mi_vector_hash.c

   1 /*      $NetBSD$        */
   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 #include <sys/cdefs.h>
  42 __RCSID("$NetBSD$");
  43
  44 #include <sys/endian.h>
  45 #include <stdint.h>
  46 #include <stdlib.h>
  47
  48 #define mix(a, b, c) do {               \
  49         a -= b; a -= c; a ^= (c >> 13); \
  50         b -= c; b -= a; b ^= (a << 8);  \
  51         c -= a; c -= b; c ^= (b >> 13); \
  52         a -= b; a -= c; a ^= (c >> 12); \
  53         b -= c; b -= a; b ^= (a << 16); \
  54         c -= a; c -= b; c ^= (b >> 5);  \
  55         a -= b; a -= c; a ^= (c >> 3);  \
  56         b -= c; b -= a; b ^= (a << 10); \
  57         c -= a; c -= b; c ^= (b >> 15); \
  58 } while (/* CONSTCOND */0)
  59
  60 #define FIXED_SEED      0x9e3779b9      /* Golden ratio, arbitrary constant */
  61
  62 void
  63 mi_vector_hash(const void * __restrict key, size_t len, uint32_t seed,
  64     uint32_t hashes[3])
  65 {
  66         static const uint32_t mask[4] = {
  67                 0x000000ff, 0x0000ffff, 0x00ffffff, 0xffffffff
  68         };
  69         uint32_t orig_len, a, b, c;
  70         const uint8_t *k;
  71
  72         orig_len = (uint32_t)len;
  73
  74         a = b = FIXED_SEED;
  75         c = seed;
  76
  77         if ((uintptr_t)key & 3) {
  78                 k = key;
  79                 while (len >= 12) {
  80                         a += le32dec(k);
  81                         b += le32dec(k + 4);
  82                         c += le32dec(k + 8);
  83                         mix(a, b, c);
  84                         k += 12;
  85                         len -= 12;
  86                 }
  87                 c += orig_len;
  88
  89                 if (len > 8) {
  90                         switch (len) {
  91                         case 11:
  92                                 c += (uint32_t)k[10] << 24;
  93                                 /* FALLTHROUGH */
  94                         case 10:
  95                                 c += (uint32_t)k[9] << 16;
  96                                 /* FALLTHROUGH */
  97                         case 9:
  98                                 c += (uint32_t)k[8] << 8;
  99                                 /* FALLTHROUGH */
 100                         }
 101                         b += le32dec(k + 4);
 102                         a += le32dec(k);
 103                 } else if (len > 4) {
 104                         switch (len) {
 105                         case 8:
 106                                 b += (uint32_t)k[7] << 24;
 107                                 /* FALLTHROUGH */
 108                         case 7:
 109                                 b += (uint32_t)k[6] << 16;
 110                                 /* FALLTHROUGH */
 111                         case 6:
 112                                 b += (uint32_t)k[5] << 8;
 113                                 /* FALLTHROUGH */
 114                         case 5:
 115                                 b += k[4];
 116                                 /* FALLTHROUGH */
 117                         }
 118                         a += le32dec(k);
 119                 } else if (len) {
 120                         switch (len) {
 121                         case 4:
 122                                 a += (uint32_t)k[3] << 24;
 123                                 /* FALLTHROUGH */
 124                         case 3:
 125                                 a += (uint32_t)k[2] << 16;
 126                                 /* FALLTHROUGH */
 127                         case 2:
 128                                 a += (uint32_t)k[1] << 8;
 129                                 /* FALLTHROUGH */
 130                         case 1:
 131                                 a += k[0];
 132                                 /* FALLTHROUGH */
 133                         }
 134                 }
 135         } else {
 136                 const uint32_t *key32 = key;
 137                 while (len >= 12) {
 138                         a += le32toh(key32[0]);
 139                         b += le32toh(key32[1]);
 140                         c += le32toh(key32[2]);
 141                         mix(a, b, c);
 142                         key32 += 3;
 143                         len -= 12;
 144                 }
 145                 c += orig_len;
 146
 147                 if (len > 8) {
 148                         c += (le32toh(key32[2]) & mask[len - 9]) << 8;
 149                         b += le32toh(key32[1]);
 150                         a += le32toh(key32[0]);
 151                 } else if (len > 4) {
 152                         b += le32toh(key32[1]) & mask[len - 5];
 153                         a += le32toh(key32[0]);
 154                 } else if (len)
 155                         a += le32toh(key32[0]) & mask[len - 1];
 156         }
 157         mix(a, b, c);
 158         hashes[0] = a;
 159         hashes[1] = b;
 160         hashes[2] = c;
 161 }