1/*
2 *  linux/fs/ext3/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/jbd.h>
14#include <linux/ext3_fs.h>
15#include <linux/cryptohash.h>
16
17#define DELTA 0x9E3779B9
18
19static void TEA_transform(__u32 buf[4], __u32 const in[])
20{
21	__u32	sum = 0;
22	__u32	b0 = buf[0], b1 = buf[1];
23	__u32	a = in[0], b = in[1], c = in[2], d = in[3];
24	int	n = 16;
25
26	do {
27		sum += DELTA;
28		b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
29		b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
30	} while(--n);
31
32	buf[0] += b0;
33	buf[1] += b1;
34}
35
36
37/* The old legacy hash */
38static __u32 dx_hack_hash (const char *name, int len)
39{
40	__u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
41	while (len--) {
42		__u32 hash = hash1 + (hash0 ^ (*name++ * 7152373));
43
44		if (hash & 0x80000000) hash -= 0x7fffffff;
45		hash1 = hash0;
46		hash0 = hash;
47	}
48	return (hash0 << 1);
49}
50
51static void str2hashbuf(const char *msg, int len, __u32 *buf, int num)
52{
53	__u32	pad, val;
54	int	i;
55
56	pad = (__u32)len | ((__u32)len << 8);
57	pad |= pad << 16;
58
59	val = pad;
60	if (len > num*4)
61		len = num * 4;
62	for (i=0; i < len; i++) {
63		if ((i % 4) == 0)
64			val = pad;
65		val = msg[i] + (val << 8);
66		if ((i % 4) == 3) {
67			*buf++ = val;
68			val = pad;
69			num--;
70		}
71	}
72	if (--num >= 0)
73		*buf++ = val;
74	while (--num >= 0)
75		*buf++ = pad;
76}
77
78/*
79 * Returns the hash of a filename.  If len is 0 and name is NULL, then
80 * this function can be used to test whether or not a hash version is
81 * supported.
82 *
83 * The seed is an 4 longword (32 bits) "secret" which can be used to
84 * uniquify a hash.  If the seed is all zero's, then some default seed
85 * may be used.
86 *
87 * A particular hash version specifies whether or not the seed is
88 * represented, and whether or not the returned hash is 32 bits or 64
89 * bits.  32 bit hashes will return 0 for the minor hash.
90 */
91int ext3fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
92{
93	__u32	hash;
94	__u32	minor_hash = 0;
95	const char	*p;
96	int		i;
97	__u32		in[8], buf[4];
98
99	/* Initialize the default seed for the hash checksum functions */
100	buf[0] = 0x67452301;
101	buf[1] = 0xefcdab89;
102	buf[2] = 0x98badcfe;
103	buf[3] = 0x10325476;
104
105	/* Check to see if the seed is all zero's */
106	if (hinfo->seed) {
107		for (i=0; i < 4; i++) {
108			if (hinfo->seed[i])
109				break;
110		}
111		if (i < 4)
112			memcpy(buf, hinfo->seed, sizeof(buf));
113	}
114
115	switch (hinfo->hash_version) {
116	case DX_HASH_LEGACY:
117		hash = dx_hack_hash(name, len);
118		break;
119	case DX_HASH_HALF_MD4:
120		p = name;
121		while (len > 0) {
122			str2hashbuf(p, len, in, 8);
123			half_md4_transform(buf, in);
124			len -= 32;
125			p += 32;
126		}
127		minor_hash = buf[2];
128		hash = buf[1];
129		break;
130	case DX_HASH_TEA:
131		p = name;
132		while (len > 0) {
133			str2hashbuf(p, len, in, 4);
134			TEA_transform(buf, in);
135			len -= 16;
136			p += 16;
137		}
138		hash = buf[0];
139		minor_hash = buf[1];
140		break;
141	default:
142		hinfo->hash = 0;
143		return -1;
144	}
145	hash = hash & ~1;
146	if (hash == (EXT3_HTREE_EOF << 1))
147		hash = (EXT3_HTREE_EOF-1) << 1;
148	hinfo->hash = hash;
149	hinfo->minor_hash = minor_hash;
150	return 0;
151}
152