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 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
  72f2fs_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}
 102