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Annotation of ircnowd/src/ngircd/hash.c, Revision 1.1.1.1

1.1       tomglok     1: /*
                      2:  * ngIRCd -- The Next Generation IRC Daemon
                      3:  * Copyright (c)2001-2014 Alexander Barton (alex@barton.de) and Contributors.
                      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:
                     12: #include "portab.h"
                     13:
                     14: /**
                     15:  * @file
                     16:  * Hash calculation
                     17:  */
                     18:
                     19: #include <assert.h>
                     20: #include <string.h>
                     21:
                     22: #include "defines.h"
                     23: #include "tool.h"
                     24:
                     25: #include "hash.h"
                     26:
                     27: static UINT32 jenkins_hash PARAMS((UINT8 *k, UINT32 length, UINT32 initval));
                     28:
                     29: /**
                     30:  * Calculate hash value for a given string.
                     31:  *
                     32:  * @param String Input string
                     33:  * @return 32 bit hash value
                     34:  */
                     35: GLOBAL UINT32
                     36: Hash( const char *String )
                     37: {
                     38:        char buffer[COMMAND_LEN];
                     39:
                     40:        strlcpy(buffer, String, sizeof(buffer));
                     41:        return jenkins_hash((UINT8 *)ngt_LowerStr(buffer),
                     42:                            (UINT32)strlen(buffer), 42);
                     43: } /* Hash */
                     44:
                     45: /*
                     46:  * This hash function originates from lookup3.c of Bob Jenkins
                     47:  * (URL: <http://burtleburtle.net/bob/c/lookup3.c>):
                     48:  * --------------------------------------------------------------------
                     49:  * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
                     50:  * These are functions for producing 32-bit hashes for hash table lookup.
                     51:  * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
                     52:  * are externally useful functions.  Routines to test the hash are included
                     53:  * if SELF_TEST is defined.  You can use this free for any purpose.  It's in
                     54:  * the public domain.  It has no warranty.
                     55:  * --------------------------------------------------------------------
                     56:  * Not all of his functions are used here.
                     57:  */
                     58:
                     59: #define hashsize(n) ((UINT32)1<<(n))
                     60: #define hashmask(n) (hashsize(n)-1)
                     61: #define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
                     62:
                     63: #define mix(a,b,c) \
                     64: { \
                     65:        a -= c;  a ^= rot(c, 4);  c += b; \
                     66:        b -= a;  b ^= rot(a, 6);  a += c; \
                     67:        c -= b;  c ^= rot(b, 8);  b += a; \
                     68:        a -= c;  a ^= rot(c,16);  c += b; \
                     69:        b -= a;  b ^= rot(a,19);  a += c; \
                     70:        c -= b;  c ^= rot(b, 4);  b += a; \
                     71: } /* mix */
                     72:
                     73: #define final(a,b,c) \
                     74: { \
                     75:        c ^= b; c -= rot(b,14); \
                     76:        a ^= c; a -= rot(c,11); \
                     77:        b ^= a; b -= rot(a,25); \
                     78:        c ^= b; c -= rot(b,16); \
                     79:        a ^= c; a -= rot(c,4);  \
                     80:        b ^= a; b -= rot(a,14); \
                     81:        c ^= b; c -= rot(b,24); \
                     82: }
                     83:
                     84: static UINT32
                     85: jenkins_hash(UINT8 *k, UINT32 length, UINT32 initval)
                     86: {
                     87:        /* k: the key
                     88:         * length: length of the key
                     89:         * initval: the previous hash, or an arbitrary value
                     90:         */
                     91:        UINT32 a,b,c;
                     92:
                     93:        /* Set up the internal state */
                     94:        a = b = c = 0xdeadbeef + length + initval;
                     95:
                     96:        /* handle most of the key */
                     97:        while (length > 12) {
                     98:                a += (k[0] +((UINT32)k[1]<<8) +((UINT32)k[2]<<16) +((UINT32)k[3]<<24));
                     99:                b += (k[4] +((UINT32)k[5]<<8) +((UINT32)k[6]<<16) +((UINT32)k[7]<<24));
                    100:                c += (k[8] +((UINT32)k[9]<<8) +((UINT32)k[10]<<16)+((UINT32)k[11]<<24));
                    101:                mix(a,b,c);
                    102:                length -= 12;
                    103:                k += 12;
                    104:        }
                    105:
                    106:        /*-------------------------------- last block: affect all 32 bits of (c) */
                    107:        switch(length)                   /* all the case statements fall through */
                    108:
                    109:        {
                    110:                case 12: c+=((UINT32)k[11])<<24;
                    111:                case 11: c+=((UINT32)k[10]<<16);
                    112:                case 10: c+=((UINT32)k[9]<<8);
                    113:                case 9 : c+=k[8];
                    114:                case 8 : b+=((UINT32)k[7]<<24);
                    115:                case 7 : b+=((UINT32)k[6]<<16);
                    116:                case 6 : b+=((UINT32)k[5]<<8);
                    117:                case 5 : b+=k[4];
                    118:                case 4 : a+=((UINT32)k[3]<<24);
                    119:                case 3 : a+=((UINT32)k[2]<<16);
                    120:                case 2 : a+=((UINT32)k[1]<<8);
                    121:                case 1 : a+=k[0];
                    122:                         break;
                    123:                case 0 : return c;
                    124:        }
                    125:        final(a,b,c);
                    126:        return c;
                    127: } /* jenkins_hash */
                    128:
                    129: /* -eof- */