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Annotation of ircnowd/src/ngircd/hash.c, Revision 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- */