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// Modified by Ingo Weinhold (bonefish), Jan. 2003:
16// Fixed r5_hash() and added key_offset_for_name().
17
18//
19// keyed_hash
20// yura_hash
21// r5_hash
22//
23
24#include "hashes.h"
25#include "reiserfs.h"
26
27#define DELTA 0x9E3779B9
28#define FULLROUNDS 10		/* 32 is overkill, 16 is strong crypto */
29#define PARTROUNDS 6		/* 6 gets complete mixing */
30
31/* a, b, c, d - data; h0, h1 - accumulated hash */
32#define TEACORE(rounds)							\
33	do {								\
34		uint32 sum = 0;						\
35		int n = rounds;						\
36		uint32 b0, b1;						\
37									\
38		b0 = h0;						\
39		b1 = h1;						\
40									\
41		do							\
42		{							\
43			sum += DELTA;					\
44			b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);	\
45			b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);	\
46		} while(--n);						\
47									\
48		h0 += b0;						\
49		h1 += b1;						\
50	} while(0)
51
52
53uint32 keyed_hash(const signed char *msg, int len)
54{
55	uint32 k[] = { 0x9464a485, 0x542e1a94, 0x3e846bff, 0xb75bcfc3};
56
57	uint32 h0 = k[0], h1 = k[1];
58	uint32 a, b, c, d;
59	uint32 pad;
60	int i;
61
62
63	//	assert(len >= 0 && len < 256);
64
65	pad = (uint32)len | ((uint32)len << 8);
66	pad |= pad << 16;
67
68	while(len >= 16)
69	{
70		a = (uint32)msg[ 0]      |
71		    (uint32)msg[ 1] << 8 |
72		    (uint32)msg[ 2] << 16|
73		    (uint32)msg[ 3] << 24;
74		b = (uint32)msg[ 4]      |
75		    (uint32)msg[ 5] << 8 |
76		    (uint32)msg[ 6] << 16|
77		    (uint32)msg[ 7] << 24;
78		c = (uint32)msg[ 8]      |
79		    (uint32)msg[ 9] << 8 |
80		    (uint32)msg[10] << 16|
81		    (uint32)msg[11] << 24;
82		d = (uint32)msg[12]      |
83		    (uint32)msg[13] << 8 |
84		    (uint32)msg[14] << 16|
85		    (uint32)msg[15] << 24;
86
87		TEACORE(PARTROUNDS);
88
89		len -= 16;
90		msg += 16;
91	}
92
93	if (len >= 12)
94	{
95	    	//assert(len < 16);
96		if (len >= 16)
97		    *(int *)0 = 0;
98
99		a = (uint32)msg[ 0]      |
100		    (uint32)msg[ 1] << 8 |
101		    (uint32)msg[ 2] << 16|
102		    (uint32)msg[ 3] << 24;
103		b = (uint32)msg[ 4]      |
104		    (uint32)msg[ 5] << 8 |
105		    (uint32)msg[ 6] << 16|
106		    (uint32)msg[ 7] << 24;
107		c = (uint32)msg[ 8]      |
108		    (uint32)msg[ 9] << 8 |
109		    (uint32)msg[10] << 16|
110		    (uint32)msg[11] << 24;
111
112		d = pad;
113		for(i = 12; i < len; i++)
114		{
115			d <<= 8;
116			d |= msg[i];
117		}
118	}
119	else if (len >= 8)
120	{
121	    	//assert(len < 12);
122		if (len >= 12)
123		    *(int *)0 = 0;
124		a = (uint32)msg[ 0]      |
125		    (uint32)msg[ 1] << 8 |
126		    (uint32)msg[ 2] << 16|
127		    (uint32)msg[ 3] << 24;
128		b = (uint32)msg[ 4]      |
129		    (uint32)msg[ 5] << 8 |
130		    (uint32)msg[ 6] << 16|
131		    (uint32)msg[ 7] << 24;
132
133		c = d = pad;
134		for(i = 8; i < len; i++)
135		{
136			c <<= 8;
137			c |= msg[i];
138		}
139	}
140	else if (len >= 4)
141	{
142	    	//assert(len < 8);
143		if (len >= 8)
144		    *(int *)0 = 0;
145		a = (uint32)msg[ 0]      |
146		    (uint32)msg[ 1] << 8 |
147		    (uint32)msg[ 2] << 16|
148		    (uint32)msg[ 3] << 24;
149
150		b = c = d = pad;
151		for(i = 4; i < len; i++)
152		{
153			b <<= 8;
154			b |= msg[i];
155		}
156	}
157	else
158	{
159	    	//assert(len < 4);
160		if (len >= 4)
161		    *(int *)0 = 0;
162		a = b = c = d = pad;
163		for(i = 0; i < len; i++)
164		{
165			a <<= 8;
166			a |= msg[i];
167		}
168	}
169
170	TEACORE(FULLROUNDS);
171
172/*	return 0;*/
173	return h0^h1;
174}
175
176/* What follows in this file is copyright 2000 by Hans Reiser, and the
177 * licensing of what follows is governed by reiserfs/README */
178
179uint32 yura_hash (const signed char *msg, int len)
180{
181    int j, pow;
182    uint32 a, c;
183    int i;
184
185    for (pow=1,i=1; i < len; i++) pow = pow * 10;
186
187    if (len == 1)
188	a = msg[0]-48;
189    else
190	a = (msg[0] - 48) * pow;
191
192    for (i=1; i < len; i++) {
193	c = msg[i] - 48;
194	for (pow=1,j=i; j < len-1; j++) pow = pow * 10;
195	a = a + c * pow;
196    }
197
198    for (; i < 40; i++) {
199	c = '0' - 48;
200	for (pow=1,j=i; j < len-1; j++) pow = pow * 10;
201	a = a + c * pow;
202    }
203
204    for (; i < 256; i++) {
205	c = i;
206	for (pow=1,j=i; j < len-1; j++) pow = pow * 10;
207	a = a + c * pow;
208    }
209
210    a = a << 7;
211    return a;
212}
213
214uint32 r5_hash (const signed char *msg, int len)
215{
216  uint32 a=0;
217// bonefish: len was ignored
218//  while(*msg) {
219  while(len--) {
220    a += *msg << 4;
221    a += *msg >> 4;
222    a *= 11;
223    msg++;
224   }
225  return a;
226}
227
228
229// bonefish:
230// from reiserfs_fs.h:
231/* hash value occupies bits from 7 up to 30 */
232#define GET_HASH_VALUE(offset) ((offset) & 0x7fffff80LL)
233#define MAX_GENERATION_NUMBER  127
234
235// bonefish:
236// derived from name.c: get_third_component()
237uint32
238key_offset_for_name(hash_function_t hash, const char *name, int len)
239{
240    uint32 res;
241
242	if (!len || (len == 1 && name[0] == '.'))
243		return DOT_OFFSET;
244	if (len == 2 && name[0] == '.' && name[1] == '.')
245		return DOT_DOT_OFFSET;
246
247	res = (*hash)((const signed char*)name, len);
248
249	// take bits from 7-th to 30-th including both bounds
250	res = GET_HASH_VALUE(res);
251	if (res == 0)
252		// needed to have no names before "." and ".." those have hash
253		// value == 0 and generation conters 1 and 2 accordingly
254		res = 128;
255	return res + MAX_GENERATION_NUMBER;
256}
257
258