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Date:	Fri, 2 Feb 2001 06:23:29 +0100 (CET)
From:	Dieter Demerre <ext DOT dieter DOT demerre AT siemens DOT be>
X-Sender:	<ddemerre AT anthony DOT siemens DOT ebp DOT ii3 DOT b-rail DOT be>
To:	<djgpp AT delorie DOT com>
Subject:	Re: Hash function
In-Reply-To:	<95cfee$m9h$1@venus.telepac.pt>
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On Thu, 1 Feb 2001, Frederico Jerónimo wrote:

>     Ex : Given 0x8ae29 the function would return 0x629
>
>     I know this is not a very efficient hash function so I was wondering if
> anyone has any ideas for a better one. Thanks in advance,

int hashpjw(const int seed, const char* s)
/*
  ACTION:
    perform some bit-operations upon the characters of s, to obtain a
    rather unique integer.  (chaotic behaviour)
    (n.b. chaotic means little changes within s chould cause huge changes
    in result)
    Refer to the Dragonbook.
 */
{
  const char* p;
  unsigned int hv = 0;
  unsigned int g;

  for ( p = s; *p; p++ ) {
    hv = (hv << 4) + (*p);
    if ((g = (hv & 0xf0000000U)) != 0U) {
      hv = hv ^ (g >> 24);
      hv = hv ^ g;
    } else {
    }
  }
  return hv % seed;
}


- -- Groetjes vanwege... Greetings from... --
- -- Dieter Demerre  ***  ddemerre AT acm DOT org --
- -- http://www.angelfire.com/de/ddemerre/ --

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