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 ((len <= 2) && (name[0] == '.') &&
83		(name[1] == '.' || name[1] == '\0'))
84		return 0;
85
86	/* Initialize the default seed for the hash checksum functions */
87	buf[0] = 0x67452301;
88	buf[1] = 0xefcdab89;
89	buf[2] = 0x98badcfe;
90	buf[3] = 0x10325476;
91
92	p = name;
93	while (1) {
94		str2hashbuf(p, len, in, 4);
95		TEA_transform(buf, in);
96		p += 16;
97		if (len <= 16)
98			break;
99		len -= 16;
100	}
101	hash = buf[0];
102	f2fs_hash = cpu_to_le32(hash & ~F2FS_HASH_COL_BIT);
103	return f2fs_hash;
104}
105