hashes.c

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    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>       /* for printk() as called by BUG() */
   22 #include <asm/types.h>
   23 #include <asm/page.h>
   24 
   25 
   26 
   27 #define DELTA 0x9E3779B9
   28 #define FULLROUNDS 10           /* 32 is overkill, 16 is strong crypto */
   29 #define PARTROUNDS 6            /* 6 gets complete mixing */
   30 
   31 /* a, b, c, d - data; h0, h1 - accumulated hash */
   32 #define TEACORE(rounds)                                                 \
   33         do {                                                            \
   34                 u32 sum = 0;                                            \
   35                 int n = rounds;                                         \
   36                 u32 b0, b1;                                             \
   37                                                                         \
   38                 b0 = h0;                                                \
   39                 b1 = h1;                                                \
   40                                                                         \
   41                 do                                                      \
   42                 {                                                       \
   43                         sum += DELTA;                                   \
   44                         b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b); \
   45                         b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d); \
   46                 } while(--n);                                           \
   47                                                                         \
   48                 h0 += b0;                                               \
   49                 h1 += b1;                                               \
   50         } while(0)
   51 
   52 
   53 u32 keyed_hash(const signed char *msg, int len)
   54 {
   55         u32 k[] = { 0x9464a485, 0x542e1a94, 0x3e846bff, 0xb75bcfc3}; 
   56 
   57         u32 h0 = k[0], h1 = k[1];
   58         u32 a, b, c, d;
   59         u32 pad;
   60         int i;
   61  
   62         //      assert(len >= 0 && len < 256);
   63 
   64         pad = (u32)len | ((u32)len << 8);
   65         pad |= pad << 16;
   66 
   67         while(len >= 16)
   68         {
   69                 a = (u32)msg[ 0]      |
   70                     (u32)msg[ 1] << 8 |
   71                     (u32)msg[ 2] << 16|
   72                     (u32)msg[ 3] << 24;
   73                 b = (u32)msg[ 4]      |
   74                     (u32)msg[ 5] << 8 |
   75                     (u32)msg[ 6] << 16|
   76                     (u32)msg[ 7] << 24;
   77                 c = (u32)msg[ 8]      |
   78                     (u32)msg[ 9] << 8 |
   79                     (u32)msg[10] << 16|
   80                     (u32)msg[11] << 24;
   81                 d = (u32)msg[12]      |
   82                     (u32)msg[13] << 8 |
   83                     (u32)msg[14] << 16|
   84                     (u32)msg[15] << 24;
   85                 
   86                 TEACORE(PARTROUNDS);
   87 
   88                 len -= 16;
   89                 msg += 16;
   90         }
   91 
   92         if (len >= 12)
   93         {
   94                 //assert(len < 16);
   95                 if (len >= 16)
   96                     BUG();
   97 
   98                 a = (u32)msg[ 0]      |
   99                     (u32)msg[ 1] << 8 |
  100                     (u32)msg[ 2] << 16|
  101                     (u32)msg[ 3] << 24;
  102                 b = (u32)msg[ 4]      |
  103                     (u32)msg[ 5] << 8 |
  104                     (u32)msg[ 6] << 16|
  105                     (u32)msg[ 7] << 24;
  106                 c = (u32)msg[ 8]      |
  107                     (u32)msg[ 9] << 8 |
  108                     (u32)msg[10] << 16|
  109                     (u32)msg[11] << 24;
  110 
  111                 d = pad;
  112                 for(i = 12; i < len; i++)
  113                 {
  114                         d <<= 8;
  115                         d |= msg[i];
  116                 }
  117         }
  118         else if (len >= 8)
  119         {
  120                 //assert(len < 12);
  121                 if (len >= 12)
  122                     BUG();
  123                 a = (u32)msg[ 0]      |
  124                     (u32)msg[ 1] << 8 |
  125                     (u32)msg[ 2] << 16|
  126                     (u32)msg[ 3] << 24;
  127                 b = (u32)msg[ 4]      |
  128                     (u32)msg[ 5] << 8 |
  129                     (u32)msg[ 6] << 16|
  130                     (u32)msg[ 7] << 24;
  131 
  132                 c = d = pad;
  133                 for(i = 8; i < len; i++)
  134                 {
  135                         c <<= 8;
  136                         c |= msg[i];
  137                 }
  138         }
  139         else if (len >= 4)
  140         {
  141                 //assert(len < 8);
  142                 if (len >= 8)
  143                     BUG();
  144                 a = (u32)msg[ 0]      |
  145                     (u32)msg[ 1] << 8 |
  146                     (u32)msg[ 2] << 16|
  147                     (u32)msg[ 3] << 24;
  148 
  149                 b = c = d = pad;
  150                 for(i = 4; i < len; i++)
  151                 {
  152                         b <<= 8;
  153                         b |= msg[i];
  154                 }
  155         }
  156         else
  157         {
  158                 //assert(len < 4);
  159                 if (len >= 4)
  160                     BUG();
  161                 a = b = c = d = pad;
  162                 for(i = 0; i < len; i++)
  163                 {
  164                         a <<= 8;
  165                         a |= msg[i];
  166                 }
  167         }
  168 
  169         TEACORE(FULLROUNDS);
  170 
  171 /*      return 0;*/
  172         return h0^h1;
  173 }
  174 
  175 /* What follows in this file is copyright 2000-2002 by Hans Reiser, and the
  176  * licensing of what follows is governed by reiserfs/README */
  177 
  178 u32 yura_hash (const signed char *msg, int len)
  179 {
  180     int j, pow;
  181     u32 a, c;
  182     int i;
  183     
  184     for (pow=1,i=1; i < len; i++) pow = pow * 10; 
  185     
  186     if (len == 1) 
  187         a = msg[0]-48;
  188     else
  189         a = (msg[0] - 48) * pow;
  190     
  191     for (i=1; i < len; i++) {
  192         c = msg[i] - 48; 
  193         for (pow=1,j=i; j < len-1; j++) pow = pow * 10; 
  194         a = a + c * pow;
  195     }
  196     
  197     for (; i < 40; i++) {
  198         c = '' - 48; 
  199         for (pow=1,j=i; j < len-1; j++) pow = pow * 10; 
  200         a = a + c * pow;
  201     }
  202     
  203     for (; i < 256; i++) {
  204         c = i; 
  205         for (pow=1,j=i; j < len-1; j++) pow = pow * 10; 
  206         a = a + c * pow;
  207     }
  208     
  209     a = a << 7;
  210     return a;
  211 }
  212 
  213 u32 r5_hash (const signed char *msg, int len)
  214 {
  215   u32 a=0;
  216   while(*msg) { 
  217     a += *msg << 4;
  218     a += *msg >> 4;
  219     a *= 11;
  220     msg++;
  221    } 
  222   return a;
  223 }

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FreeBSD/Linux Kernel Cross Reference sys/fs/reiserfs/hashes.c

FreeBSD/Linux Kernel Cross Reference
sys/fs/reiserfs/hashes.c