fs/f2fs/hash.c

   1 /*
   2  * fs/f2fs/hash.c
   3  *
   4  * Copyright (c) 2012 Samsung Electronics Co., Ltd.
   5  *             http://www.samsung.com/
   6  *
   7  * Portions of this code from linux/fs/ext3/hash.c
   8  *
   9  * Copyright (C) 2002 by Theodore Ts'o
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License version 2 as
  13  * published by the Free Software Foundation.
  14  */
  15 #include <linux/types.h>
  16 #include <linux/fs.h>
  17 #include <linux/f2fs_fs.h>
  18 #include <linux/cryptohash.h>
  19 #include <linux/pagemap.h>
  20
  21 #include "f2fs.h"
  22
  23 /*
  24  * Hashing code copied from ext3
  25  */
  26 #define DELTA 0x9E3779B9
  27
  28 static void TEA_transform(unsigned int buf[4], unsigned int const in[])
  29 {
  30         __u32 sum = 0;
  31         __u32 b0 = buf[0], b1 = buf[1];
  32         __u32 a = in[0], b = in[1], c = in[2], d = in[3];
  33         int n = 16;
  34
  35         do {
  36                 sum += DELTA;
  37                 b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
  38                 b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
  39         } while (--n);
  40
  41         buf[0] += b0;
  42         buf[1] += b1;
  43 }
  44
  45 static void str2hashbuf(const char *msg, size_t len, unsigned int *buf, int num)
  46 {
  47         unsigned pad, val;
  48         int i;
  49
  50         pad = (__u32)len | ((__u32)len << 8);
  51         pad |= pad << 16;
  52
  53         val = pad;
  54         if (len > num * 4)
  55                 len = num * 4;
  56         for (i = 0; i < len; i++) {
  57                 if ((i % 4) == 0)
  58                         val = pad;
  59                 val = msg[i] + (val << 8);
  60                 if ((i % 4) == 3) {
  61                         *buf++ = val;
  62                         val = pad;
  63                         num--;
  64                 }
  65         }
  66         if (--num >= 0)
  67                 *buf++ = val;
  68         while (--num >= 0)
  69                 *buf++ = pad;
  70 }
  71
  72 f2fs_hash_t f2fs_dentry_hash(const char *name, size_t len)
  73 {
  74         __u32 hash;
  75         f2fs_hash_t f2fs_hash;
  76         const char *p;
  77         __u32 in[8], buf[4];
  78
  79         if ((len <= 2) && (name[0] == '.') &&
  80                 (name[1] == '.' || name[1] == '\0'))
  81                 return 0;
  82
  83         /* Initialize the default seed for the hash checksum functions */
  84         buf[0] = 0x67452301;
  85         buf[1] = 0xefcdab89;
  86         buf[2] = 0x98badcfe;
  87         buf[3] = 0x10325476;
  88
  89         p = name;
  90         while (1) {
  91                 str2hashbuf(p, len, in, 4);
  92                 TEA_transform(buf, in);
  93                 p += 16;
  94                 if (len <= 16)
  95                         break;
  96                 len -= 16;
  97         }
  98         hash = buf[0];
  99         f2fs_hash = cpu_to_le32(hash & ~F2FS_HASH_COL_BIT);
 100         return f2fs_hash;
 101 }