linux/fs/ext3/hash.c
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   1/*
   2 *  linux/fs/ext3/hash.c
   3 *
   4 * Copyright (C) 2002 by Theodore Ts'o
   5 *
   6 * This file is released under the GPL v2.
   7 *
   8 * This file may be redistributed under the terms of the GNU Public
   9 * License.
  10 */
  11
  12#include "ext3.h"
  13#include <linux/cryptohash.h>
  14
  15#define DELTA 0x9E3779B9
  16
  17static void TEA_transform(__u32 buf[4], __u32 const in[])
  18{
  19        __u32   sum = 0;
  20        __u32   b0 = buf[0], b1 = buf[1];
  21        __u32   a = in[0], b = in[1], c = in[2], d = in[3];
  22        int     n = 16;
  23
  24        do {
  25                sum += DELTA;
  26                b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
  27                b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
  28        } while(--n);
  29
  30        buf[0] += b0;
  31        buf[1] += b1;
  32}
  33
  34
  35/* The old legacy hash */
  36static __u32 dx_hack_hash_unsigned(const char *name, int len)
  37{
  38        __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
  39        const unsigned char *ucp = (const unsigned char *) name;
  40
  41        while (len--) {
  42                hash = hash1 + (hash0 ^ (((int) *ucp++) * 7152373));
  43
  44                if (hash & 0x80000000)
  45                        hash -= 0x7fffffff;
  46                hash1 = hash0;
  47                hash0 = hash;
  48        }
  49        return hash0 << 1;
  50}
  51
  52static __u32 dx_hack_hash_signed(const char *name, int len)
  53{
  54        __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
  55        const signed char *scp = (const signed char *) name;
  56
  57        while (len--) {
  58                hash = hash1 + (hash0 ^ (((int) *scp++) * 7152373));
  59
  60                if (hash & 0x80000000)
  61                        hash -= 0x7fffffff;
  62                hash1 = hash0;
  63                hash0 = hash;
  64        }
  65        return hash0 << 1;
  66}
  67
  68static void str2hashbuf_signed(const char *msg, int len, __u32 *buf, int num)
  69{
  70        __u32   pad, val;
  71        int     i;
  72        const signed char *scp = (const signed char *) msg;
  73
  74        pad = (__u32)len | ((__u32)len << 8);
  75        pad |= pad << 16;
  76
  77        val = pad;
  78        if (len > num*4)
  79                len = num * 4;
  80        for (i = 0; i < len; i++) {
  81                if ((i % 4) == 0)
  82                        val = pad;
  83                val = ((int) scp[i]) + (val << 8);
  84                if ((i % 4) == 3) {
  85                        *buf++ = val;
  86                        val = pad;
  87                        num--;
  88                }
  89        }
  90        if (--num >= 0)
  91                *buf++ = val;
  92        while (--num >= 0)
  93                *buf++ = pad;
  94}
  95
  96static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num)
  97{
  98        __u32   pad, val;
  99        int     i;
 100        const unsigned char *ucp = (const unsigned char *) msg;
 101
 102        pad = (__u32)len | ((__u32)len << 8);
 103        pad |= pad << 16;
 104
 105        val = pad;
 106        if (len > num*4)
 107                len = num * 4;
 108        for (i=0; i < len; i++) {
 109                if ((i % 4) == 0)
 110                        val = pad;
 111                val = ((int) ucp[i]) + (val << 8);
 112                if ((i % 4) == 3) {
 113                        *buf++ = val;
 114                        val = pad;
 115                        num--;
 116                }
 117        }
 118        if (--num >= 0)
 119                *buf++ = val;
 120        while (--num >= 0)
 121                *buf++ = pad;
 122}
 123
 124/*
 125 * Returns the hash of a filename.  If len is 0 and name is NULL, then
 126 * this function can be used to test whether or not a hash version is
 127 * supported.
 128 *
 129 * The seed is an 4 longword (32 bits) "secret" which can be used to
 130 * uniquify a hash.  If the seed is all zero's, then some default seed
 131 * may be used.
 132 *
 133 * A particular hash version specifies whether or not the seed is
 134 * represented, and whether or not the returned hash is 32 bits or 64
 135 * bits.  32 bit hashes will return 0 for the minor hash.
 136 */
 137int ext3fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
 138{
 139        __u32   hash;
 140        __u32   minor_hash = 0;
 141        const char      *p;
 142        int             i;
 143        __u32           in[8], buf[4];
 144        void            (*str2hashbuf)(const char *, int, __u32 *, int) =
 145                                str2hashbuf_signed;
 146
 147        /* Initialize the default seed for the hash checksum functions */
 148        buf[0] = 0x67452301;
 149        buf[1] = 0xefcdab89;
 150        buf[2] = 0x98badcfe;
 151        buf[3] = 0x10325476;
 152
 153        /* Check to see if the seed is all zero's */
 154        if (hinfo->seed) {
 155                for (i=0; i < 4; i++) {
 156                        if (hinfo->seed[i])
 157                                break;
 158                }
 159                if (i < 4)
 160                        memcpy(buf, hinfo->seed, sizeof(buf));
 161        }
 162
 163        switch (hinfo->hash_version) {
 164        case DX_HASH_LEGACY_UNSIGNED:
 165                hash = dx_hack_hash_unsigned(name, len);
 166                break;
 167        case DX_HASH_LEGACY:
 168                hash = dx_hack_hash_signed(name, len);
 169                break;
 170        case DX_HASH_HALF_MD4_UNSIGNED:
 171                str2hashbuf = str2hashbuf_unsigned;
 172        case DX_HASH_HALF_MD4:
 173                p = name;
 174                while (len > 0) {
 175                        (*str2hashbuf)(p, len, in, 8);
 176                        half_md4_transform(buf, in);
 177                        len -= 32;
 178                        p += 32;
 179                }
 180                minor_hash = buf[2];
 181                hash = buf[1];
 182                break;
 183        case DX_HASH_TEA_UNSIGNED:
 184                str2hashbuf = str2hashbuf_unsigned;
 185        case DX_HASH_TEA:
 186                p = name;
 187                while (len > 0) {
 188                        (*str2hashbuf)(p, len, in, 4);
 189                        TEA_transform(buf, in);
 190                        len -= 16;
 191                        p += 16;
 192                }
 193                hash = buf[0];
 194                minor_hash = buf[1];
 195                break;
 196        default:
 197                hinfo->hash = 0;
 198                return -1;
 199        }
 200        hash = hash & ~1;
 201        if (hash == (EXT3_HTREE_EOF_32BIT << 1))
 202                hash = (EXT3_HTREE_EOF_32BIT - 1) << 1;
 203        hinfo->hash = hash;
 204        hinfo->minor_hash = minor_hash;
 205        return 0;
 206}
 207
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