1 /*
2  * ngIRCd -- The Next Generation IRC Daemon
3  * Copyright (c)2001,2002 by Alexander Barton (alex@barton.de)
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License as published by
7  * the Free Software Foundation; either version 2 of the License, or
8  * (at your option) any later version.
9  * Please read the file COPYING, README and AUTHORS for more information.
10  *
11  * Hash calculation
12  */
13 
14 
15 #include "portab.h"
16 
17 static char UNUSED id[] = "$Id: hash.c,v 1.9 2002/12/26 16:25:43 alex Exp $";
18 
19 #include "imp.h"
20 #include <assert.h>
21 #include <string.h>
22 
23 #include "defines.h"
24 #include "log.h"
25 #include "tool.h"
26 
27 #include "exp.h"
28 #include "hash.h"
29 
30 
31 LOCAL UINT32 jenkins_hash PARAMS(( register UINT8 *k, register UINT32 length, register UINT32 initval ));
32 
33 
34 GLOBAL UINT32
35 Hash( CHAR *String )
36 {
37 	/* Hash-Wert ueber String berechnen */
38 
39 	CHAR buffer[LINE_LEN];
40 
41 	strlcpy( buffer, String, sizeof( buffer ));
42 	return jenkins_hash( (UINT8 *)ngt_LowerStr( buffer ), strlen( buffer ), 42 );
43 } /* Hash */
44 
45 
46 /*
47  * Die hier verwendete Hash-Funktion stammt aus lookup2.c von Bob Jenkins
48  * (URL: <http://burtleburtle.net/bob/c/lookup2.c>). Aus dem Header:
49  * --------------------------------------------------------------------
50  * lookup2.c, by Bob Jenkins, December 1996, Public Domain.
51  * hash(), hash2(), hash3, and mix() are externally useful functions.
52  * Routines to test the hash are included if SELF_TEST is defined.
53  * You can use this free for any purpose.  It has no warranty.
54  * --------------------------------------------------------------------
55  * nicht alle seiner Funktionen werden hier genutzt.
56  */
57 
58 
59 #define hashsize(n) ((UINT32)1<<(n))
60 #define hashmask(n) (hashsize(n)-1)
61 
62 #define mix(a,b,c) \
63 { \
64 	a -= b; a -= c; a ^= (c>>13); \
65 	b -= c; b -= a; b ^= (a<<8);  \
66 	c -= a; c -= b; c ^= (b>>13); \
67 	a -= b; a -= c; a ^= (c>>12); \
68 	b -= c; b -= a; b ^= (a<<16); \
69 	c -= a; c -= b; c ^= (b>>5);  \
70 	a -= b; a -= c; a ^= (c>>3);  \
71 	b -= c; b -= a; b ^= (a<<10); \
72 	c -= a; c -= b; c ^= (b>>15); \
73 } /* mix */
74 
75 
76 LOCAL UINT32
77 jenkins_hash( register UINT8 *k, register UINT32 length, register UINT32 initval )
78 {
79 	/* k: the key
80 	 * length: length of the key
81 	 * initval: the previous hash, or an arbitrary value
82 	 */
83 
84 	register UINT32 a,b,c,len;
85 
86 	/* Set up the internal state */
87 	len = length;
88 	a = b = 0x9e3779b9;	/* the golden ratio; an arbitrary value */
89 	c = initval;		/* the previous hash value */
90 
91 	/* handle most of the key */
92 	while (len >= 12)
93 	{
94 		a += (k[0] +((UINT32)k[1]<<8) +((UINT32)k[2]<<16) +((UINT32)k[3]<<24));
95 		b += (k[4] +((UINT32)k[5]<<8) +((UINT32)k[6]<<16) +((UINT32)k[7]<<24));
96 		c += (k[8] +((UINT32)k[9]<<8) +((UINT32)k[10]<<16)+((UINT32)k[11]<<24));
97 		mix(a,b,c);
98 		k += 12; len -= 12;
99 	}
100 
101 	/* handle the last 11 bytes */
102 	c += length;
103 	switch( (INT)len )	/* all the case statements fall through */
104 	{
105 		case 11: c+=((UINT32)k[10]<<24);
106 		case 10: c+=((UINT32)k[9]<<16);
107 		case 9 : c+=((UINT32)k[8]<<8);
108 		/* the first byte of c is reserved for the length */
109 		case 8 : b+=((UINT32)k[7]<<24);
110 		case 7 : b+=((UINT32)k[6]<<16);
111 		case 6 : b+=((UINT32)k[5]<<8);
112 		case 5 : b+=k[4];
113 		case 4 : a+=((UINT32)k[3]<<24);
114 		case 3 : a+=((UINT32)k[2]<<16);
115 		case 2 : a+=((UINT32)k[1]<<8);
116 		case 1 : a+=k[0];
117 		/* case 0: nothing left to add */
118 	}
119 	mix(a,b,c);
120 
121 	/* report the result */
122 	return c;
123 } /* jenkins_hash */
124 
125 
126 /* -eof- */