pierre@1: <?php
pierre@1: // $Id: ad_weight_probability.inc,v 1.1.4.3 2009/02/28 05:48:42 jeremy Exp $
pierre@1: 
pierre@1: /**
pierre@1:  * @file
pierre@1:  * A plug in for the ad.module, allowing an admin to set the probability that
pierre@1:  * a given advertisement will be displayed.
pierre@1:  *
pierre@1:  * Copyright (c) 2008-2009.
pierre@1:  *  Jeremy Andrews <jeremy@tag1consulting.com>.
pierre@1:  */
pierre@1: 
pierre@1: function ad_weight_probability_cache_filter($ads) {
pierre@1:   $display = array();
pierre@1:   if (is_array($ads)) {
pierre@1:     $probability = array();
pierre@1:     $cache = adserve_cache('get_cache', 'weight');
pierre@1:     foreach ($ads as $aid) {
pierre@1:       $probability[] = isset($cache['probability'][$aid]) ? $cache['probability'][$aid] : 0;
pierre@1:     }
pierre@1:     $gcd = ad_weight_probability_gcd($probability);
pierre@1:     _debug_echo("ad_weight_probability cache_filter gcd($gcd)");
pierre@1:     foreach ($ads as $aid) {
pierre@1:       $weight = (isset($cache['probability'][$aid]) && $gcd) ? $cache['probability'][$aid] / $gcd : 0;
pierre@1:       _debug_echo("ad_weight_probability cache_filter aid($aid) weight($weight)");
pierre@1:       for ($i = 1; $i <= $weight; $i++) {
pierre@1:         $display[] = $aid;
pierre@1:       }
pierre@1:     }
pierre@1:   }
pierre@1:   return $display;
pierre@1: }
pierre@1: 
pierre@1: /**
pierre@1:  * Returns the greatest common divisor of an array of integers.
pierre@1:  */
pierre@1: function ad_weight_probability_gcd($integers) {
pierre@1:   $gcd = array_shift($integers);
pierre@1: 
pierre@1:   while (!empty($integers)) {
pierre@1:     $gcd = _ad_weight_probability_gcd($gcd, array_shift($integers));
pierre@1:   }
pierre@1:   return $gcd;
pierre@1: }
pierre@1: 
pierre@1: /**
pierre@1:  * Helper function to calculate the greatest common divisor using the Euclidean
pierre@1:  * algorithm (http://en.wikipedia.org/wiki/Euclidean_algorithm).
pierre@1:  */
pierre@1: function _ad_weight_probability_gcd($a, $b) {
pierre@1:   if ($b == 0) {
pierre@1:     return $a;
pierre@1:   }
pierre@1:   else {
pierre@1:     return _ad_weight_probability_gcd($b, $a % $b);
pierre@1:   }
pierre@1: }