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 "ext3.h"
  13 #include <linux/cryptohash.h>
  14
  15 #define DELTA 0x9E3779B9
  16
  17 static 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 */
  36 static __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
  52 static __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
  68 static 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
  96 static 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  */
 137 int 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 }