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 <asm/types.h>
  23 #include <asm/bug.h>
  24
  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
  52 u32 keyed_hash(const signed char *msg, int len)
  53 {
  54         u32 k[] = { 0x9464a485, 0x542e1a94, 0x3e846bff, 0xb75bcfc3};
  55
  56         u32 h0 = k[0], h1 = k[1];
  57         u32 a, b, c, d;
  58         u32 pad;
  59         int i;
  60
  61         //      assert(len >= 0 && len < 256);
  62
  63         pad = (u32)len | ((u32)len << 8);
  64         pad |= pad << 16;
  65
  66         while(len >= 16)
  67         {
  68                 a = (u32)msg[ 0]      |
  69                     (u32)msg[ 1] << 8 |
  70                     (u32)msg[ 2] << 16|
  71                     (u32)msg[ 3] << 24;
  72                 b = (u32)msg[ 4]      |
  73                     (u32)msg[ 5] << 8 |
  74                     (u32)msg[ 6] << 16|
  75                     (u32)msg[ 7] << 24;
  76                 c = (u32)msg[ 8]      |
  77                     (u32)msg[ 9] << 8 |
  78                     (u32)msg[10] << 16|
  79                     (u32)msg[11] << 24;
  80                 d = (u32)msg[12]      |
  81                     (u32)msg[13] << 8 |
  82                     (u32)msg[14] << 16|
  83                     (u32)msg[15] << 24;
  84
  85                 TEACORE(PARTROUNDS);
  86
  87                 len -= 16;
  88                 msg += 16;
  89         }
  90
  91         if (len >= 12)
  92         {
  93                 a = (u32)msg[ 0]      |
  94                     (u32)msg[ 1] << 8 |
  95                     (u32)msg[ 2] << 16|
  96                     (u32)msg[ 3] << 24;
  97                 b = (u32)msg[ 4]      |
  98                     (u32)msg[ 5] << 8 |
  99                     (u32)msg[ 6] << 16|
 100                     (u32)msg[ 7] << 24;
 101                 c = (u32)msg[ 8]      |
 102                     (u32)msg[ 9] << 8 |
 103                     (u32)msg[10] << 16|
 104                     (u32)msg[11] << 24;
 105
 106                 d = pad;
 107                 for(i = 12; i < len; i++)
 108                 {
 109                         d <<= 8;
 110                         d |= msg[i];
 111                 }
 112         }
 113         else if (len >= 8)
 114         {
 115                 a = (u32)msg[ 0]      |
 116                     (u32)msg[ 1] << 8 |
 117                     (u32)msg[ 2] << 16|
 118                     (u32)msg[ 3] << 24;
 119                 b = (u32)msg[ 4]      |
 120                     (u32)msg[ 5] << 8 |
 121                     (u32)msg[ 6] << 16|
 122                     (u32)msg[ 7] << 24;
 123
 124                 c = d = pad;
 125                 for(i = 8; i < len; i++)
 126                 {
 127                         c <<= 8;
 128                         c |= msg[i];
 129                 }
 130         }
 131         else if (len >= 4)
 132         {
 133                 a = (u32)msg[ 0]      |
 134                     (u32)msg[ 1] << 8 |
 135                     (u32)msg[ 2] << 16|
 136                     (u32)msg[ 3] << 24;
 137
 138                 b = c = d = pad;
 139                 for(i = 4; i < len; i++)
 140                 {
 141                         b <<= 8;
 142                         b |= msg[i];
 143                 }
 144         }
 145         else
 146         {
 147                 a = b = c = d = pad;
 148                 for(i = 0; i < len; i++)
 149                 {
 150                         a <<= 8;
 151                         a |= msg[i];
 152                 }
 153         }
 154
 155         TEACORE(FULLROUNDS);
 156
 157 /*      return 0;*/
 158         return h0^h1;
 159 }
 160
 161 /* What follows in this file is copyright 2000 by Hans Reiser, and the
 162  * licensing of what follows is governed by reiserfs/README */
 163
 164 u32 yura_hash (const signed char *msg, int len)
 165 {
 166     int j, pow;
 167     u32 a, c;
 168     int i;
 169
 170     for (pow=1,i=1; i < len; i++) pow = pow * 10;
 171
 172     if (len == 1)
 173         a = msg[0]-48;
 174     else
 175         a = (msg[0] - 48) * pow;
 176
 177     for (i=1; i < len; i++) {
 178         c = msg[i] - 48;
 179         for (pow=1,j=i; j < len-1; j++) pow = pow * 10;
 180         a = a + c * pow;
 181     }
 182
 183     for (; i < 40; i++) {
 184         c = '0' - 48;
 185         for (pow=1,j=i; j < len-1; j++) pow = pow * 10;
 186         a = a + c * pow;
 187     }
 188
 189     for (; i < 256; i++) {
 190         c = i;
 191         for (pow=1,j=i; j < len-1; j++) pow = pow * 10;
 192         a = a + c * pow;
 193     }
 194
 195     a = a << 7;
 196     return a;
 197 }
 198
 199 u32 r5_hash (const signed char *msg, int len)
 200 {
 201   u32 a=0;
 202   while(*msg) {
 203     a += *msg << 4;
 204     a += *msg >> 4;
 205     a *= 11;
 206     msg++;
 207    }
 208   return a;
 209 }