1
2/*
3 * Keyed 32-bit hash function using TEA in a Davis-Meyer function
4 *   H0 = Key
5 *   Hi = E Mi(Hi-1) + Hi-1
6 *
7 * (see Applied Cryptography, 2nd edition, p448).
8 *
9 * Jeremy Fitzhardinge <jeremy@zip.com.au> 1998
10 *
11 * Jeremy has agreed to the contents of reiserfs/README. -Hans
12 * Yura's function is added (04/07/2000)
13 */
14
15//
16// keyed_hash
17// yura_hash
18// r5_hash
19//
20
21#include <linux/kernel.h>
22#include <linux/reiserfs_fs.h>
23#include <asm/types.h>
24
25#define DELTA 0x9E3779B9
26#define FULLROUNDS 10		/* 32 is overkill, 16 is strong crypto */
27#define PARTROUNDS 6		/* 6 gets complete mixing */
28
29/* a, b, c, d - data; h0, h1 - accumulated hash */
30#define TEACORE(rounds)							\
31	do {								\
32		u32 sum = 0;						\
33		int n = rounds;						\
34		u32 b0, b1;						\
35									\
36		b0 = h0;						\
37		b1 = h1;						\
38									\
39		do							\
40		{							\
41			sum += DELTA;					\
42			b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);	\
43			b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);	\
44		} while(--n);						\
45									\
46		h0 += b0;						\
47		h1 += b1;						\
48	} while(0)
49
50u32 keyed_hash(const signed char *msg, int len)
51{
52	u32 k[] = { 0x9464a485, 0x542e1a94, 0x3e846bff, 0xb75bcfc3 };
53
54	u32 h0 = k[0], h1 = k[1];
55	u32 a, b, c, d;
56	u32 pad;
57	int i;
58
59	//      assert(len >= 0 && len < 256);
60
61	pad = (u32) len | ((u32) len << 8);
62	pad |= pad << 16;
63
64	while (len >= 16) {
65		a = (u32) msg[0] |
66		    (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
67		b = (u32) msg[4] |
68		    (u32) msg[5] << 8 | (u32) msg[6] << 16 | (u32) msg[7] << 24;
69		c = (u32) msg[8] |
70		    (u32) msg[9] << 8 |
71		    (u32) msg[10] << 16 | (u32) msg[11] << 24;
72		d = (u32) msg[12] |
73		    (u32) msg[13] << 8 |
74		    (u32) msg[14] << 16 | (u32) msg[15] << 24;
75
76		TEACORE(PARTROUNDS);
77
78		len -= 16;
79		msg += 16;
80	}
81
82	if (len >= 12) {
83		a = (u32) msg[0] |
84		    (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
85		b = (u32) msg[4] |
86		    (u32) msg[5] << 8 | (u32) msg[6] << 16 | (u32) msg[7] << 24;
87		c = (u32) msg[8] |
88		    (u32) msg[9] << 8 |
89		    (u32) msg[10] << 16 | (u32) msg[11] << 24;
90
91		d = pad;
92		for (i = 12; i < len; i++) {
93			d <<= 8;
94			d |= msg[i];
95		}
96	} else if (len >= 8) {
97		a = (u32) msg[0] |
98		    (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
99		b = (u32) msg[4] |
100		    (u32) msg[5] << 8 | (u32) msg[6] << 16 | (u32) msg[7] << 24;
101
102		c = d = pad;
103		for (i = 8; i < len; i++) {
104			c <<= 8;
105			c |= msg[i];
106		}
107	} else if (len >= 4) {
108		a = (u32) msg[0] |
109		    (u32) msg[1] << 8 | (u32) msg[2] << 16 | (u32) msg[3] << 24;
110
111		b = c = d = pad;
112		for (i = 4; i < len; i++) {
113			b <<= 8;
114			b |= msg[i];
115		}
116	} else {
117		a = b = c = d = pad;
118		for (i = 0; i < len; i++) {
119			a <<= 8;
120			a |= msg[i];
121		}
122	}
123
124	TEACORE(FULLROUNDS);
125
126/*	return 0;*/
127	return h0 ^ h1;
128}
129
130/* What follows in this file is copyright 2000 by Hans Reiser, and the
131 * licensing of what follows is governed by reiserfs/README */
132
133u32 yura_hash(const signed char *msg, int len)
134{
135	int j, pow;
136	u32 a, c;
137	int i;
138
139	for (pow = 1, i = 1; i < len; i++)
140		pow = pow * 10;
141
142	if (len == 1)
143		a = msg[0] - 48;
144	else
145		a = (msg[0] - 48) * pow;
146
147	for (i = 1; i < len; i++) {
148		c = msg[i] - 48;
149		for (pow = 1, j = i; j < len - 1; j++)
150			pow = pow * 10;
151		a = a + c * pow;
152	}
153
154	for (; i < 40; i++) {
155		c = '0' - 48;
156		for (pow = 1, j = i; j < len - 1; j++)
157			pow = pow * 10;
158		a = a + c * pow;
159	}
160
161	for (; i < 256; i++) {
162		c = i;
163		for (pow = 1, j = i; j < len - 1; j++)
164			pow = pow * 10;
165		a = a + c * pow;
166	}
167
168	a = a << 7;
169	return a;
170}
171
172u32 r5_hash(const signed char *msg, int len)
173{
174	u32 a = 0;
175	while (*msg) {
176		a += *msg << 4;
177		a += *msg >> 4;
178		a *= 11;
179		msg++;
180	}
181	return a;
182}
183