library/HTMLPurifier/URISchemeRegistry.php

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<?php

class HTMLPurifier_URISchemeRegistry
{
    
    public static function instance($prototype = null) {
        static $instance = null;
        if ($prototype !== null) {
            $instance = $prototype;
        } elseif ($instance === null || $prototype == true) {
            $instance = new HTMLPurifier_URISchemeRegistry();
        }
        return $instance;
    }
    
    protected $schemes = array();
    
    public function getScheme($scheme, $config, $context) {
        if (!$config) $config = HTMLPurifier_Config::createDefault();
        $null = null; // for the sake of passing by reference
        
        // important, otherwise attacker could include arbitrary file
        $allowed_schemes = $config->get('URI', 'AllowedSchemes');
        if (!$config->get('URI', 'OverrideAllowedSchemes') &&
            !isset($allowed_schemes[$scheme])
        ) {
            return $null;
        }
        
        if (isset($this->schemes[$scheme])) return $this->schemes[$scheme];
        if (!isset($allowed_schemes[$scheme])) return $null;
        
        $class = 'HTMLPurifier_URIScheme_' . $scheme;
        if (!class_exists($class)) return $null;
        $this->schemes[$scheme] = new $class();
        return $this->schemes[$scheme];
    }
    
    public function register($scheme, $scheme_obj) {
        $this->schemes[$scheme] = $scheme_obj;
    }
    
}

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