fs/ext3/hash.c

   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 <linux/fs.h>
  13 #include <linux/jbd.h>
  14 #include <linux/sched.h>
  15 #include <linux/ext3_fs.h>
  16 #include <linux/cryptohash.h>
  17
  18 #define DELTA 0x9E3779B9
  19
  20 static void TEA_transform(__u32 buf[4], __u32 const in[])
  21 {
  22         __u32   sum = 0;
  23         __u32   b0 = buf[0], b1 = buf[1];
  24         __u32   a = in[0], b = in[1], c = in[2], d = in[3];
  25         int     n = 16;
  26
  27         do {
  28                 sum += DELTA;
  29                 b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
  30                 b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
  31         } while(--n);
  32
  33         buf[0] += b0;
  34         buf[1] += b1;
  35 }
  36
  37
  38 /* The old legacy hash */
  39 static __u32 dx_hack_hash (const char *name, int len)
  40 {
  41         __u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
  42         while (len--) {
  43                 __u32 hash = hash1 + (hash0 ^ (*name++ * 7152373));
  44
  45                 if (hash & 0x80000000) hash -= 0x7fffffff;
  46                 hash1 = hash0;
  47                 hash0 = hash;
  48         }
  49         return (hash0 << 1);
  50 }
  51
  52 static void str2hashbuf(const char *msg, int len, __u32 *buf, int num)
  53 {
  54         __u32   pad, val;
  55         int     i;
  56
  57         pad = (__u32)len | ((__u32)len << 8);
  58         pad |= pad << 16;
  59
  60         val = pad;
  61         if (len > num*4)
  62                 len = num * 4;
  63         for (i=0; i < len; i++) {
  64                 if ((i % 4) == 0)
  65                         val = pad;
  66                 val = msg[i] + (val << 8);
  67                 if ((i % 4) == 3) {
  68                         *buf++ = val;
  69                         val = pad;
  70                         num--;
  71                 }
  72         }
  73         if (--num >= 0)
  74                 *buf++ = val;
  75         while (--num >= 0)
  76                 *buf++ = pad;
  77 }
  78
  79 /*
  80  * Returns the hash of a filename.  If len is 0 and name is NULL, then
  81  * this function can be used to test whether or not a hash version is
  82  * supported.
  83  *
  84  * The seed is an 4 longword (32 bits) "secret" which can be used to
  85  * uniquify a hash.  If the seed is all zero's, then some default seed
  86  * may be used.
  87  *
  88  * A particular hash version specifies whether or not the seed is
  89  * represented, and whether or not the returned hash is 32 bits or 64
  90  * bits.  32 bit hashes will return 0 for the minor hash.
  91  */
  92 int ext3fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
  93 {
  94         __u32   hash;
  95         __u32   minor_hash = 0;
  96         const char      *p;
  97         int             i;
  98         __u32           in[8], buf[4];
  99
 100         /* Initialize the default seed for the hash checksum functions */
 101         buf[0] = 0x67452301;
 102         buf[1] = 0xefcdab89;
 103         buf[2] = 0x98badcfe;
 104         buf[3] = 0x10325476;
 105
 106         /* Check to see if the seed is all zero's */
 107         if (hinfo->seed) {
 108                 for (i=0; i < 4; i++) {
 109                         if (hinfo->seed[i])
 110                                 break;
 111                 }
 112                 if (i < 4)
 113                         memcpy(buf, hinfo->seed, sizeof(buf));
 114         }
 115
 116         switch (hinfo->hash_version) {
 117         case DX_HASH_LEGACY:
 118                 hash = dx_hack_hash(name, len);
 119                 break;
 120         case DX_HASH_HALF_MD4:
 121                 p = name;
 122                 while (len > 0) {
 123                         str2hashbuf(p, len, in, 8);
 124                         half_md4_transform(buf, in);
 125                         len -= 32;
 126                         p += 32;
 127                 }
 128                 minor_hash = buf[2];
 129                 hash = buf[1];
 130                 break;
 131         case DX_HASH_TEA:
 132                 p = name;
 133                 while (len > 0) {
 134                         str2hashbuf(p, len, in, 4);
 135                         TEA_transform(buf, in);
 136                         len -= 16;
 137                         p += 16;
 138                 }
 139                 hash = buf[0];
 140                 minor_hash = buf[1];
 141                 break;
 142         default:
 143                 hinfo->hash = 0;
 144                 return -1;
 145         }
 146         hash = hash & ~1;
 147         if (hash == (EXT3_HTREE_EOF << 1))
 148                 hash = (EXT3_HTREE_EOF-1) << 1;
 149         hinfo->hash = hash;
 150         hinfo->minor_hash = minor_hash;
 151         return 0;
 152 }