PHP - код для подсчета PR Checksum

Скрипт базируется на новом алгоритме от Гугла:

<?php

/*

        Written and contributed by

        Alex Stapleton,

        Andy Doctorow,

        Tarakan,

        Bill Zeller,

        Vijay "Cyberax" Bhatter

        traB

    This code is released into the public domain

*/

header("Content-Type: text/plain; charset=utf-8");

define('GOOGLE_MAGIC', 0xE6359A60);



//unsigned shift right

function zeroFill($a, $b)

{

    $z = hexdec(80000000);

        if ($z & $a)

        {

            $a = ($a>>1);

            $a &= (~$z);

            $a |= 0x40000000;

            $a = ($a>>($b-1));

        }

        else

        {

            $a = ($a>>$b);

        }

        return $a;

}





function mix($a,$b,$c) {

  $a -= $b; $a -= $c; $a ^= (zeroFill($c,13));

  $b -= $c; $b -= $a; $b ^= ($a<<8);

  $c -= $a; $c -= $b; $c ^= (zeroFill($b,13));

  $a -= $b; $a -= $c; $a ^= (zeroFill($c,12));

  $b -= $c; $b -= $a; $b ^= ($a<<16);

  $c -= $a; $c -= $b; $c ^= (zeroFill($b,5));

  $a -= $b; $a -= $c; $a ^= (zeroFill($c,3));  

  $b -= $c; $b -= $a; $b ^= ($a<<10);

  $c -= $a; $c -= $b; $c ^= (zeroFill($b,15));

  

  return array($a,$b,$c);

}



function GoogleCH($url, $length=null, $init=GOOGLE_MAGIC) {

    if(is_null($length)) {

        $length = sizeof($url);

    }

    $a = $b = 0x9E3779B9;

    $c = $init;

    $k = 0;

    $len = $length;

    while($len >= 12) {

        $a += ($url[$k+0] +($url[$k+1]<<8) +($url[$k+2]<<16) +($url[$k+3]<<24));

        $b += ($url[$k+4] +($url[$k+5]<<8) +($url[$k+6]<<16) +($url[$k+7]<<24));

        $c += ($url[$k+8] +($url[$k+9]<<8) +($url[$k+10]<<16)+($url[$k+11]<<24));

        $mix = mix($a,$b,$c);

        $a = $mix[0]; $b = $mix[1]; $c = $mix[2];

        $k += 12;

        $len -= 12;

    }



    $c += $length;

    switch($len)              /* all the case statements fall through */

    {

        case 11: $c+=($url[$k+10]<<24);

        case 10: $c+=($url[$k+9]<<16);

        case 9 : $c+=($url[$k+8]<<8);

          /* the first byte of c is reserved for the length */

        case 8 : $b+=($url[$k+7]<<24);

        case 7 : $b+=($url[$k+6]<<16);

        case 6 : $b+=($url[$k+5]<<8);

        case 5 : $b+=($url[$k+4]);

        case 4 : $a+=($url[$k+3]<<24);

        case 3 : $a+=($url[$k+2]<<16);

        case 2 : $a+=($url[$k+1]<<8);

        case 1 : $a+=($url[$k+0]);

         /* case 0: nothing left to add */

    }

    $mix = mix($a,$b,$c);

    /*-------------------------------------------- report the result */

    return $mix[2];

}



//converts a string into an array of integers containing 

//the numeric value of the char



function strord($string) {

    for($i=0;$i<strlen($string);$i++) {

        $result[$i] = ord($string{$i});

    }

    return $result;

}





// converts an array of 32 bit integers into an array with 

//8 bit values. Equivalent to (BYTE *)arr32



function c32to8bit($arr32) {

    for($i=0;$i<count($arr32);$i++) {

        for ($bitOrder=$i*4;$bitOrder<=$i*4+3;$bitOrder++) {

            $arr8[$bitOrder]=$arr32[$i]&255;

            $arr32[$i]=zeroFill($arr32[$i], 8);

        }    

    }

    return $arr8;

}





// http://www.example.com/ - Checksum: 6540747202

$url = 'info:'.$_GET['url'];

print("url:\t{$_GET['url']}\n");

$ch = GoogleCH(strord($url));

printf("Checksum <2.0.114:\t6%u\n",$ch);



$ch=sprintf("%u", $ch);

// new since Toolbar 2.0.114



$ch = ((($ch/7) << 2) | (((int)fmod($ch,13))&7));



$prbuf = array();

$prbuf[0] = $ch;

for($i = 1; $i < 20; $i++) {

      $prbuf[$i] = $prbuf[$i-1]-9;

}

$ch = GoogleCH(c32to8bit($prbuf), 80);

//



printf("Checksum >=2.0.114:\t6%u\n",$ch);

?>

Источник: http://blog.outer-court.com/archive/2004_09_16_index.html#109533285150852715