LXR linux/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
  28static 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
  45static void str2hashbuf(const unsigned char *msg, size_t len,
  46                                unsigned int *buf, int num)
  47{
  48        unsigned pad, val;
  49        int i;
  50
  51        pad = (__u32)len | ((__u32)len << 8);
  52        pad |= pad << 16;
  53
  54        val = pad;
  55        if (len > num * 4)
  56                len = num * 4;
  57        for (i = 0; i < len; i++) {
  58                if ((i % 4) == 0)
  59                        val = pad;
  60                val = msg[i] + (val << 8);
  61                if ((i % 4) == 3) {
  62                        *buf++ = val;
  63                        val = pad;
  64                        num--;
  65                }
  66        }
  67        if (--num >= 0)
  68                *buf++ = val;
  69        while (--num >= 0)
  70                *buf++ = pad;
  71}
  72
  73f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info)
  74{
  75        __u32 hash;
  76        f2fs_hash_t f2fs_hash;
  77        const unsigned char *p;
  78        __u32 in[8], buf[4];
  79        const unsigned char *name = name_info->name;
  80        size_t len = name_info->len;
  81
  82        if (is_dot_dotdot(name_info))
  83                return 0;
  84
  85        /* Initialize the default seed for the hash checksum functions */
  86        buf[0] = 0x67452301;
  87        buf[1] = 0xefcdab89;
  88        buf[2] = 0x98badcfe;
  89        buf[3] = 0x10325476;
  90
  91        p = name;
  92        while (1) {
  93                str2hashbuf(p, len, in, 4);
  94                TEA_transform(buf, in);
  95                p += 16;
  96                if (len <= 16)
  97                        break;
  98                len -= 16;
  99        }
 100        hash = buf[0];
 101        f2fs_hash = cpu_to_le32(hash & ~F2FS_HASH_COL_BIT);
 102        return f2fs_hash;
 103}
 104