fs/reiserfs/hashes.c

   1
   2 /*
   3  * Keyed 32-bit hash function using TEA in a Davis-Meyer function
   4  *   H0 = Key
   5  *   Hi = E Mi(Hi-1) + Hi-1
   6  *
   7  * (see Applied Cryptography, 2nd edition, p448).
   8  *
   9  * Jeremy Fitzhardinge <jeremy@zip.com.au> 1998
  10  *
  11  * Jeremy has agreed to the contents of reiserfs/README. -Hans
  12  * Yura's function is added (04/07/2000)
  13  */
  14
  15 #include <linux/kernel.h>
  16 #include "reiserfs.h"
  17 #include <asm/types.h>
  18
  19 #define DELTA 0x9E3779B9
  20 #define FULLROUNDS 10           /* 32 is overkill, 16 is strong crypto */
  21 #define PARTROUNDS 6            /* 6 gets complete mixing */
  22
  23 /* a, b, c, d - data; h0, h1 - accumulated hash */
  24 #define TEACORE(rounds)                                                 \
  25         do {                                                            \
  26                 u32 sum = 0;                                            \
  27                 int n = rounds;                                         \
  28                 u32 b0, b1;                                             \
  29                                                                         \
  30                 b0 = h0;                                                \
  31                 b1 = h1;                                                \
  32                                                                         \
  33                 do                                                      \
  34                 {                                                       \
  35                         sum += DELTA;                                   \
  36                         b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b); \
  37                         b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d); \
  38                 } while(--n);                                           \
  39                                                                         \
  40                 h0 += b0;                                               \
  41                 h1 += b1;                                               \
  42         } while(0)
  43
  44 u32 keyed_hash(const signed char *msg, int len)
  45 {
  46         u32 k[] = { 0x9464a485, 0x542e1a94, 0x3e846bff, 0xb75bcfc3 };
  47
  48         u32 h0 = k[0], h1 = k[1];
  49         u32 a, b, c, d;
  50         u32 pad;
  51         int i;
  52
  53         /*      assert(len >= 0 && len < 256); */
  54
  55         pad = (u32) len | ((u32) len << 8);
  56         pad |= pad << 16;
  57
  58         while (len >= 16) {
  59                 a = (u32) msg[0] |
  60                     (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
  61                 b = (u32) msg[4] |
  62                     (u32) msg[5] << 8 | (u32) msg[6] << 16 | (u32) msg[7] << 24;
  63                 c = (u32) msg[8] |
  64                     (u32) msg[9] << 8 |
  65                     (u32) msg[10] << 16 | (u32) msg[11] << 24;
  66                 d = (u32) msg[12] |
  67                     (u32) msg[13] << 8 |
  68                     (u32) msg[14] << 16 | (u32) msg[15] << 24;
  69
  70                 TEACORE(PARTROUNDS);
  71
  72                 len -= 16;
  73                 msg += 16;
  74         }
  75
  76         if (len >= 12) {
  77                 a = (u32) msg[0] |
  78                     (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
  79                 b = (u32) msg[4] |
  80                     (u32) msg[5] << 8 | (u32) msg[6] << 16 | (u32) msg[7] << 24;
  81                 c = (u32) msg[8] |
  82                     (u32) msg[9] << 8 |
  83                     (u32) msg[10] << 16 | (u32) msg[11] << 24;
  84
  85                 d = pad;
  86                 for (i = 12; i < len; i++) {
  87                         d <<= 8;
  88                         d |= msg[i];
  89                 }
  90         } else if (len >= 8) {
  91                 a = (u32) msg[0] |
  92                     (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
  93                 b = (u32) msg[4] |
  94                     (u32) msg[5] << 8 | (u32) msg[6] << 16 | (u32) msg[7] << 24;
  95
  96                 c = d = pad;
  97                 for (i = 8; i < len; i++) {
  98                         c <<= 8;
  99                         c |= msg[i];
 100                 }
 101         } else if (len >= 4) {
 102                 a = (u32) msg[0] |
 103                     (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
 104
 105                 b = c = d = pad;
 106                 for (i = 4; i < len; i++) {
 107                         b <<= 8;
 108                         b |= msg[i];
 109                 }
 110         } else {
 111                 a = b = c = d = pad;
 112                 for (i = 0; i < len; i++) {
 113                         a <<= 8;
 114                         a |= msg[i];
 115                 }
 116         }
 117
 118         TEACORE(FULLROUNDS);
 119
 120 /*      return 0;*/
 121         return h0 ^ h1;
 122 }
 123
 124 /*
 125  * What follows in this file is copyright 2000 by Hans Reiser, and the
 126  * licensing of what follows is governed by reiserfs/README
 127  */
 128 u32 yura_hash(const signed char *msg, int len)
 129 {
 130         int j, pow;
 131         u32 a, c;
 132         int i;
 133
 134         for (pow = 1, i = 1; i < len; i++)
 135                 pow = pow * 10;
 136
 137         if (len == 1)
 138                 a = msg[0] - 48;
 139         else
 140                 a = (msg[0] - 48) * pow;
 141
 142         for (i = 1; i < len; i++) {
 143                 c = msg[i] - 48;
 144                 for (pow = 1, j = i; j < len - 1; j++)
 145                         pow = pow * 10;
 146                 a = a + c * pow;
 147         }
 148
 149         for (; i < 40; i++) {
 150                 c = '0' - 48;
 151                 for (pow = 1, j = i; j < len - 1; j++)
 152                         pow = pow * 10;
 153                 a = a + c * pow;
 154         }
 155
 156         for (; i < 256; i++) {
 157                 c = i;
 158                 for (pow = 1, j = i; j < len - 1; j++)
 159                         pow = pow * 10;
 160                 a = a + c * pow;
 161         }
 162
 163         a = a << 7;
 164         return a;
 165 }
 166
 167 u32 r5_hash(const signed char *msg, int len)
 168 {
 169         u32 a = 0;
 170         while (*msg) {
 171                 a += *msg << 4;
 172                 a += *msg >> 4;
 173                 a *= 11;
 174                 msg++;
 175         }
 176         return a;
 177 }