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