linux/fs/reiserfs/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>
  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
  50u32 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
 133u32 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
 172u32 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}
 183
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