Google PageRank的计算源代码

最近对google的PageRank(网页等级)比较感兴趣，一直想知道如何不用google toolbar来获取pr值。苦苦搜索之后,找到如下代码:

<?php

/

This code is released unto the public doma

/

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

defe('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, $it=GOOGLE_MAGIC) {

if(is_null($length)) {

$length = sizeof($url);

}

$a = $b = 0x9E3779B9;

$c = $it;

$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: nothg left to add /

}

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

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

return $mix[2];

}

//converts a strg to an array of tegers contag the numeric value of the char

function strord($strg) {

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

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

}

return $result;

}

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

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

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

$url='fo:'.urlencode($_GET['url']);

echo file_get_contents("http://.google./search?client=navclient-auto&ch=6$ch&ie=UTF-8&oe=UTF-8&features=Rank&q=$url");

/ use curl send the user angent

$curl = curl_it("http://.google./search?client=navclient-auto&ch=6$ch&ie=UTF-8&oe=UTF-8&features=Rank&q=$url");

curl_set ($curl, CURLOPT_USERAGENT, "Mozilla/4.0 (patible; GoogleToolbar 2.0.110-big; Wdows 2000 5.0)");

curl_exec($curl);

/

?>

</></>

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