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 //
  16 // keyed_hash
  17 // yura_hash
  18 // r5_hash
  19 //
  20
  21 #include <linux/kernel.h>
  22 #include <linux/reiserfs_fs.h>
  23 #include <asm/types.h>
  24 #include <asm/bug.h>
  25
  26 #define DELTA 0x9E3779B9
  27 #define FULLROUNDS 10           /* 32 is overkill, 16 is strong crypto */
  28 #define PARTROUNDS 6            /* 6 gets complete mixing */
  29
  30 /* a, b, c, d - data; h0, h1 - accumulated hash */
  31 #define TEACORE(rounds)                                                 \
  32         do {                                                            \
  33                 u32 sum = 0;                                            \
  34                 int n = rounds;                                         \
  35                 u32 b0, b1;                                             \
  36                                                                         \
  37                 b0 = h0;                                                \
  38                 b1 = h1;                                                \
  39                                                                         \
  40                 do                                                      \
  41                 {                                                       \
  42                         sum += DELTA;                                   \
  43                         b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b); \
  44                         b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d); \
  45                 } while(--n);                                           \
  46                                                                         \
  47                 h0 += b0;                                               \
  48                 h1 += b1;                                               \
  49         } while(0)
  50
  51 u32 keyed_hash(const signed char *msg, int len)
  52 {
  53         u32 k[] = { 0x9464a485, 0x542e1a94, 0x3e846bff, 0xb75bcfc3 };
  54
  55         u32 h0 = k[0], h1 = k[1];
  56         u32 a, b, c, d;
  57         u32 pad;
  58         int i;
  59
  60         //      assert(len >= 0 && len < 256);
  61
  62         pad = (u32) len | ((u32) len << 8);
  63         pad |= pad << 16;
  64
  65         while (len >= 16) {
  66                 a = (u32) msg[0] |
  67                     (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
  68                 b = (u32) msg[4] |
  69                     (u32) msg[5] << 8 | (u32) msg[6] << 16 | (u32) msg[7] << 24;
  70                 c = (u32) msg[8] |
  71                     (u32) msg[9] << 8 |
  72                     (u32) msg[10] << 16 | (u32) msg[11] << 24;
  73                 d = (u32) msg[12] |
  74                     (u32) msg[13] << 8 |
  75                     (u32) msg[14] << 16 | (u32) msg[15] << 24;
  76
  77                 TEACORE(PARTROUNDS);
  78
  79                 len -= 16;
  80                 msg += 16;
  81         }
  82
  83         if (len >= 12) {
  84                 a = (u32) msg[0] |
  85                     (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
  86                 b = (u32) msg[4] |
  87                     (u32) msg[5] << 8 | (u32) msg[6] << 16 | (u32) msg[7] << 24;
  88                 c = (u32) msg[8] |
  89                     (u32) msg[9] << 8 |
  90                     (u32) msg[10] << 16 | (u32) msg[11] << 24;
  91
  92                 d = pad;
  93                 for (i = 12; i < len; i++) {
  94                         d <<= 8;
  95                         d |= msg[i];
  96                 }
  97         } else if (len >= 8) {
  98                 a = (u32) msg[0] |
  99                     (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
 100                 b = (u32) msg[4] |
 101                     (u32) msg[5] << 8 | (u32) msg[6] << 16 | (u32) msg[7] << 24;
 102
 103                 c = d = pad;
 104                 for (i = 8; i < len; i++) {
 105                         c <<= 8;
 106                         c |= msg[i];
 107                 }
 108         } else if (len >= 4) {
 109                 a = (u32) msg[0] |
 110                     (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
 111
 112                 b = c = d = pad;
 113                 for (i = 4; i < len; i++) {
 114                         b <<= 8;
 115                         b |= msg[i];
 116                 }
 117         } else {
 118                 a = b = c = d = pad;
 119                 for (i = 0; i < len; i++) {
 120                         a <<= 8;
 121                         a |= msg[i];
 122                 }
 123         }
 124
 125         TEACORE(FULLROUNDS);
 126
 127 /*      return 0;*/
 128         return h0 ^ h1;
 129 }
 130
 131 /* What follows in this file is copyright 2000 by Hans Reiser, and the
 132  * licensing of what follows is governed by reiserfs/README */
 133
 134 u32 yura_hash(const signed char *msg, int len)
 135 {
 136         int j, pow;
 137         u32 a, c;
 138         int i;
 139
 140         for (pow = 1, i = 1; i < len; i++)
 141                 pow = pow * 10;
 142
 143         if (len == 1)
 144                 a = msg[0] - 48;
 145         else
 146                 a = (msg[0] - 48) * pow;
 147
 148         for (i = 1; i < len; i++) {
 149                 c = msg[i] - 48;
 150                 for (pow = 1, j = i; j < len - 1; j++)
 151                         pow = pow * 10;
 152                 a = a + c * pow;
 153         }
 154
 155         for (; i < 40; i++) {
 156                 c = '0' - 48;
 157                 for (pow = 1, j = i; j < len - 1; j++)
 158                         pow = pow * 10;
 159                 a = a + c * pow;
 160         }
 161
 162         for (; i < 256; i++) {
 163                 c = i;
 164                 for (pow = 1, j = i; j < len - 1; j++)
 165                         pow = pow * 10;
 166                 a = a + c * pow;
 167         }
 168
 169         a = a << 7;
 170         return a;
 171 }
 172
 173 u32 r5_hash(const signed char *msg, int len)
 174 {
 175         u32 a = 0;
 176         while (*msg) {
 177                 a += *msg << 4;
 178                 a += *msg >> 4;
 179                 a *= 11;
 180                 msg++;
 181         }
 182         return a;
 183 }