1 /*
2  * ngIRCd -- The Next Generation IRC Daemon
3  * Copyright (c)2001,2002 by Alexander Barton (alex@barton.de)
4  *
5  * Dieses Programm ist freie Software. Sie koennen es unter den Bedingungen
6  * der GNU General Public License (GPL), wie von der Free Software Foundation
7  * herausgegeben, weitergeben und/oder modifizieren, entweder unter Version 2
8  * der Lizenz oder (wenn Sie es wuenschen) jeder spaeteren Version.
9  * Naehere Informationen entnehmen Sie bitter der Datei COPYING. Eine Liste
10  * der an ngIRCd beteiligten Autoren finden Sie in der Datei AUTHORS.
11  *
12  * $Id: hash.c,v 1.5 2002/05/27 12:54:07 alex Exp $
13  *
14  * hash.c: Hash-Werte berechnen
15  */
16 
17 
18 #include "portab.h"
19 
20 #include "imp.h"
21 #include <assert.h>
22 #include <string.h>
23 
24 #include "defines.h"
25 #include "log.h"
26 #include "tool.h"
27 
28 #include "exp.h"
29 #include "hash.h"
30 
31 
32 LOCAL UINT32 jenkins_hash PARAMS(( register UINT8 *k, register UINT32 length, register UINT32 initval ));
33 
34 
35 GLOBAL UINT32
36 Hash( CHAR *String )
37 {
38 	/* Hash-Wert ueber String berechnen */
39 
40 	CHAR buffer[LINE_LEN];
41 
42 	strncpy( buffer, String, LINE_LEN - 1 );
43 	buffer[LINE_LEN - 1] = '\0';
44 	
45 	return jenkins_hash( (UINT8 *)ngt_LowerStr( buffer ), strlen( buffer ), 42 );
46 } /* Hash */
47 
48 
49 /*
50  * Die hier verwendete Hash-Funktion stammt aus lookup2.c von Bob Jenkins
51  * (URL: <http://burtleburtle.net/bob/c/lookup2.c>). Aus dem Header:
52  * --------------------------------------------------------------------
53  * lookup2.c, by Bob Jenkins, December 1996, Public Domain.
54  * hash(), hash2(), hash3, and mix() are externally useful functions.
55  * Routines to test the hash are included if SELF_TEST is defined.
56  * You can use this free for any purpose.  It has no warranty.
57  * --------------------------------------------------------------------
58  * nicht alle seiner Funktionen werden hier genutzt.
59  */
60 
61 
62 #define hashsize(n) ((UINT32)1<<(n))
63 #define hashmask(n) (hashsize(n)-1)
64 
65 #define mix(a,b,c) \
66 { \
67 	a -= b; a -= c; a ^= (c>>13); \
68 	b -= c; b -= a; b ^= (a<<8);  \
69 	c -= a; c -= b; c ^= (b>>13); \
70 	a -= b; a -= c; a ^= (c>>12); \
71 	b -= c; b -= a; b ^= (a<<16); \
72 	c -= a; c -= b; c ^= (b>>5);  \
73 	a -= b; a -= c; a ^= (c>>3);  \
74 	b -= c; b -= a; b ^= (a<<10); \
75 	c -= a; c -= b; c ^= (b>>15); \
76 } /* mix */
77 
78 
79 LOCAL UINT32
80 jenkins_hash( register UINT8 *k, register UINT32 length, register UINT32 initval )
81 {
82 	/* k: the key
83 	 * length: length of the key
84 	 * initval: the previous hash, or an arbitrary value
85 	 */
86 
87 	register UINT32 a,b,c,len;
88 
89 	/* Set up the internal state */
90 	len = length;
91 	a = b = 0x9e3779b9;	/* the golden ratio; an arbitrary value */
92 	c = initval;		/* the previous hash value */
93 
94 	/* handle most of the key */
95 	while (len >= 12)
96 	{
97 		a += (k[0] +((UINT32)k[1]<<8) +((UINT32)k[2]<<16) +((UINT32)k[3]<<24));
98 		b += (k[4] +((UINT32)k[5]<<8) +((UINT32)k[6]<<16) +((UINT32)k[7]<<24));
99 		c += (k[8] +((UINT32)k[9]<<8) +((UINT32)k[10]<<16)+((UINT32)k[11]<<24));
100 		mix(a,b,c);
101 		k += 12; len -= 12;
102 	}
103 
104 	/* handle the last 11 bytes */
105 	c += length;
106 	switch(len)		/* all the case statements fall through */
107 	{
108 		case 11: c+=((UINT32)k[10]<<24);
109 		case 10: c+=((UINT32)k[9]<<16);
110 		case 9 : c+=((UINT32)k[8]<<8);
111 		/* the first byte of c is reserved for the length */
112 		case 8 : b+=((UINT32)k[7]<<24);
113 		case 7 : b+=((UINT32)k[6]<<16);
114 		case 6 : b+=((UINT32)k[5]<<8);
115 		case 5 : b+=k[4];
116 		case 4 : a+=((UINT32)k[3]<<24);
117 		case 3 : a+=((UINT32)k[2]<<16);
118 		case 2 : a+=((UINT32)k[1]<<8);
119 		case 1 : a+=k[0];
120 		/* case 0: nothing left to add */
121 	}
122 	mix(a,b,c);
123 
124 	/* report the result */
125 	return c;
126 } /* jenkins_hash */
127 
128 
129 /* -eof- */