fs/ext4/hash.c

   1 /*
   2  *  linux/fs/ext4/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/cryptohash.h>
  14 #include "ext4.h"
  15
  16 #define DELTA 0x9E3779B9
  17
  18 static void TEA_transform(__u32 buf[4], __u32 const in[])
  19 {
  20         __u32   sum = 0;
  21         __u32   b0 = buf[0], b1 = buf[1];
  22         __u32   a = in[0], b = in[1], c = in[2], d = in[3];
  23         int     n = 16;
  24
  25         do {
  26                 sum += DELTA;
  27                 b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
  28                 b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
  29         } while (--n);
  30
  31         buf[0] += b0;
  32         buf[1] += b1;
  33 }
  34
  35
  36 /* The old legacy hash */
  37 static __u32 dx_hack_hash_unsigned(const char *name, int len)
  38 {
  39         __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
  40         const unsigned char *ucp = (const unsigned char *) name;
  41
  42         while (len--) {
  43                 hash = hash1 + (hash0 ^ (((int) *ucp++) * 7152373));
  44
  45                 if (hash & 0x80000000)
  46                         hash -= 0x7fffffff;
  47                 hash1 = hash0;
  48                 hash0 = hash;
  49         }
  50         return hash0 << 1;
  51 }
  52
  53 static __u32 dx_hack_hash_signed(const char *name, int len)
  54 {
  55         __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
  56         const signed char *scp = (const signed char *) name;
  57
  58         while (len--) {
  59                 hash = hash1 + (hash0 ^ (((int) *scp++) * 7152373));
  60
  61                 if (hash & 0x80000000)
  62                         hash -= 0x7fffffff;
  63                 hash1 = hash0;
  64                 hash0 = hash;
  65         }
  66         return hash0 << 1;
  67 }
  68
  69 static void str2hashbuf_signed(const char *msg, int len, __u32 *buf, int num)
  70 {
  71         __u32   pad, val;
  72         int     i;
  73         const signed char *scp = (const signed char *) msg;
  74
  75         pad = (__u32)len | ((__u32)len << 8);
  76         pad |= pad << 16;
  77
  78         val = pad;
  79         if (len > num*4)
  80                 len = num * 4;
  81         for (i = 0; i < len; i++) {
  82                 if ((i % 4) == 0)
  83                         val = pad;
  84                 val = ((int) scp[i]) + (val << 8);
  85                 if ((i % 4) == 3) {
  86                         *buf++ = val;
  87                         val = pad;
  88                         num--;
  89                 }
  90         }
  91         if (--num >= 0)
  92                 *buf++ = val;
  93         while (--num >= 0)
  94                 *buf++ = pad;
  95 }
  96
  97 static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num)
  98 {
  99         __u32   pad, val;
 100         int     i;
 101         const unsigned char *ucp = (const unsigned char *) msg;
 102
 103         pad = (__u32)len | ((__u32)len << 8);
 104         pad |= pad << 16;
 105
 106         val = pad;
 107         if (len > num*4)
 108                 len = num * 4;
 109         for (i = 0; i < len; i++) {
 110                 if ((i % 4) == 0)
 111                         val = pad;
 112                 val = ((int) ucp[i]) + (val << 8);
 113                 if ((i % 4) == 3) {
 114                         *buf++ = val;
 115                         val = pad;
 116                         num--;
 117                 }
 118         }
 119         if (--num >= 0)
 120                 *buf++ = val;
 121         while (--num >= 0)
 122                 *buf++ = pad;
 123 }
 124
 125 /*
 126  * Returns the hash of a filename.  If len is 0 and name is NULL, then
 127  * this function can be used to test whether or not a hash version is
 128  * supported.
 129  *
 130  * The seed is an 4 longword (32 bits) "secret" which can be used to
 131  * uniquify a hash.  If the seed is all zero's, then some default seed
 132  * may be used.
 133  *
 134  * A particular hash version specifies whether or not the seed is
 135  * represented, and whether or not the returned hash is 32 bits or 64
 136  * bits.  32 bit hashes will return 0 for the minor hash.
 137  */
 138 int ext4fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
 139 {
 140         __u32   hash;
 141         __u32   minor_hash = 0;
 142         const char      *p;
 143         int             i;
 144         __u32           in[8], buf[4];
 145         void            (*str2hashbuf)(const char *, int, __u32 *, int) =
 146                                 str2hashbuf_signed;
 147
 148         /* Initialize the default seed for the hash checksum functions */
 149         buf[0] = 0x67452301;
 150         buf[1] = 0xefcdab89;
 151         buf[2] = 0x98badcfe;
 152         buf[3] = 0x10325476;
 153
 154         /* Check to see if the seed is all zero's */
 155         if (hinfo->seed) {
 156                 for (i = 0; i < 4; i++) {
 157                         if (hinfo->seed[i]) {
 158                                 memcpy(buf, hinfo->seed, sizeof(buf));
 159                                 break;
 160                         }
 161                 }
 162         }
 163
 164         switch (hinfo->hash_version) {
 165         case DX_HASH_LEGACY_UNSIGNED:
 166                 hash = dx_hack_hash_unsigned(name, len);
 167                 break;
 168         case DX_HASH_LEGACY:
 169                 hash = dx_hack_hash_signed(name, len);
 170                 break;
 171         case DX_HASH_HALF_MD4_UNSIGNED:
 172                 str2hashbuf = str2hashbuf_unsigned;
 173         case DX_HASH_HALF_MD4:
 174                 p = name;
 175                 while (len > 0) {
 176                         (*str2hashbuf)(p, len, in, 8);
 177                         half_md4_transform(buf, in);
 178                         len -= 32;
 179                         p += 32;
 180                 }
 181                 minor_hash = buf[2];
 182                 hash = buf[1];
 183                 break;
 184         case DX_HASH_TEA_UNSIGNED:
 185                 str2hashbuf = str2hashbuf_unsigned;
 186         case DX_HASH_TEA:
 187                 p = name;
 188                 while (len > 0) {
 189                         (*str2hashbuf)(p, len, in, 4);
 190                         TEA_transform(buf, in);
 191                         len -= 16;
 192                         p += 16;
 193                 }
 194                 hash = buf[0];
 195                 minor_hash = buf[1];
 196                 break;
 197         default:
 198                 hinfo->hash = 0;
 199                 return -1;
 200         }
 201         hash = hash & ~1;
 202         if (hash == (EXT4_HTREE_EOF_32BIT << 1))
 203                 hash = (EXT4_HTREE_EOF_32BIT - 1) << 1;
 204         hinfo->hash = hash;
 205         hinfo->minor_hash = minor_hash;
 206         return 0;
 207 }