<?php

function getchecksum($MerchantId,$Amount,$OrderId ,$URL,$WorkingKey)
{
	$str ="$MerchantId|$OrderId|$Amount|$URL|$WorkingKey";
	$adler = 1;
	$adler = adler32($adler,$str);
	return $adler;
}

function verifychecksum($MerchantId,$OrderId,$Amount,$AuthDesc,$CheckSum,$WorkingKey)
{
	$str = "$MerchantId|$OrderId|$Amount|$AuthDesc|$WorkingKey";
	$adler = 1;
	$adler = adler32($adler,$str);
	
	if($adler == $CheckSum)
		return "true" ;
	else
		return "false" ;
}

function adler32($adler , $str)
{
	$BASE =  65521 ;

	$s1 = $adler & 0xffff ;
	$s2 = ($adler >> 16) & 0xffff;
	for($i = 0 ; $i < strlen($str) ; $i++)
	{
		$s1 = ($s1 + Ord($str[$i])) % $BASE ;
		$s2 = ($s2 + $s1) % $BASE ;
			//echo "s1 : $s1 <BR> s2 : $s2 <BR>";

	}
	return leftshift($s2 , 16) + $s1;
}

function leftshift($str , $num)
{

	$str = DecBin($str);

	for( $i = 0 ; $i < (64 - strlen($str)) ; $i++)
		$str = "0".$str ;

	for($i = 0 ; $i < $num ; $i++) 
	{
		$str = $str."0";
		$str = substr($str , 1 ) ;
		//echo "str : $str <BR>";
	}
	return cdec($str) ;
}

function cdec($num)
{
	$dec = 0;
	for ($n = 0 ; $n < strlen($num) ; $n++)
	{
	   $temp = $num[$n] ;
	   $dec =  $dec + $temp*pow(2 , strlen($num) - $n - 1);
	}

	return $dec;
}
?>