root/fs/reiserfs/hashes.c

DEFINITIONS

1. keyed_hash
2. yura_hash
3. r5_hash

/*
 * Keyed 32-bit hash function using TEA in a Davis-Meyer function
 *   H0 = Key
 *   Hi = E Mi(Hi-1) + Hi-1
 *
 * (see Applied Cryptography, 2nd edition, p448).
 *
 * Jeremy Fitzhardinge <jeremy@zip.com.au> 1998
 * 
 * Jeremy has agreed to the contents of reiserfs/README. -Hans
 * Yura's function is added (04/07/2000)
 */

//
// keyed_hash
// yura_hash
// r5_hash
//

#include <linux/kernel.h>
#include <linux/reiserfs_fs.h>
#include <asm/types.h>

#define DELTA 0x9E3779B9
#define FULLROUNDS 10           /* 32 is overkill, 16 is strong crypto */
#define PARTROUNDS 6            /* 6 gets complete mixing */

/* a, b, c, d - data; h0, h1 - accumulated hash */
#define TEACORE(rounds)                                                 \
        do {                                                            \
                u32 sum = 0;                                            \
                int n = rounds;                                         \
                u32 b0, b1;                                             \
                                                                        \
                b0 = h0;                                                \
                b1 = h1;                                                \
                                                                        \
                do                                                      \
                {                                                       \
                        sum += DELTA;                                   \
                        b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b); \
                        b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d); \
                } while(--n);                                           \
                                                                        \
                h0 += b0;                                               \
                h1 += b1;                                               \
        } while(0)

u32 keyed_hash(const signed char *msg, int len)
{
        u32 k[] = { 0x9464a485, 0x542e1a94, 0x3e846bff, 0xb75bcfc3 };

        u32 h0 = k[0], h1 = k[1];
        u32 a, b, c, d;
        u32 pad;
        int i;

        //      assert(len >= 0 && len < 256);

        pad = (u32) len | ((u32) len << 8);
        pad |= pad << 16;

        while (len >= 16) {
                a = (u32) msg[0] |
                    (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
                b = (u32) msg[4] |
                    (u32) msg[5] << 8 | (u32) msg[6] << 16 | (u32) msg[7] << 24;
                c = (u32) msg[8] |
                    (u32) msg[9] << 8 |
                    (u32) msg[10] << 16 | (u32) msg[11] << 24;
                d = (u32) msg[12] |
                    (u32) msg[13] << 8 |
                    (u32) msg[14] << 16 | (u32) msg[15] << 24;

                TEACORE(PARTROUNDS);

                len -= 16;
                msg += 16;
        }

        if (len >= 12) {
                a = (u32) msg[0] |
                    (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
                b = (u32) msg[4] |
                    (u32) msg[5] << 8 | (u32) msg[6] << 16 | (u32) msg[7] << 24;
                c = (u32) msg[8] |
                    (u32) msg[9] << 8 |
                    (u32) msg[10] << 16 | (u32) msg[11] << 24;

                d = pad;
                for (i = 12; i < len; i++) {
                        d <<= 8;
                        d |= msg[i];
                }
        } else if (len >= 8) {
                a = (u32) msg[0] |
                    (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
                b = (u32) msg[4] |
                    (u32) msg[5] << 8 | (u32) msg[6] << 16 | (u32) msg[7] << 24;

                c = d = pad;
                for (i = 8; i < len; i++) {
                        c <<= 8;
                        c |= msg[i];
                }
        } else if (len >= 4) {
                a = (u32) msg[0] |
                    (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;

                b = c = d = pad;
                for (i = 4; i < len; i++) {
                        b <<= 8;
                        b |= msg[i];
                }
        } else {
                a = b = c = d = pad;
                for (i = 0; i < len; i++) {
                        a <<= 8;
                        a |= msg[i];
                }
        }

        TEACORE(FULLROUNDS);

/*      return 0;*/
        return h0 ^ h1;
}

/* What follows in this file is copyright 2000 by Hans Reiser, and the
 * licensing of what follows is governed by reiserfs/README */

u32 yura_hash(const signed char *msg, int len)
{
        int j, pow;
        u32 a, c;
        int i;

        for (pow = 1, i = 1; i < len; i++)
                pow = pow * 10;

        if (len == 1)
                a = msg[0] - 48;
        else
                a = (msg[0] - 48) * pow;

        for (i = 1; i < len; i++) {
                c = msg[i] - 48;
                for (pow = 1, j = i; j < len - 1; j++)
                        pow = pow * 10;
                a = a + c * pow;
        }

        for (; i < 40; i++) {
                c = '0' - 48;
                for (pow = 1, j = i; j < len - 1; j++)
                        pow = pow * 10;
                a = a + c * pow;
        }

        for (; i < 256; i++) {
                c = i;
                for (pow = 1, j = i; j < len - 1; j++)
                        pow = pow * 10;
                a = a + c * pow;
        }

        a = a << 7;
        return a;
}

u32 r5_hash(const signed char *msg, int len)
{
        u32 a = 0;
        while (*msg) {
                a += *msg << 4;
                a += *msg >> 4;
                a *= 11;
                msg++;
        }
        return a;
}