Class.ServerDav.php

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<?php
/*
 * @author Anakeen
 * @package FDL
*/
/**
 * Virtual base class for implementing WebDAV servers
 *
 * WebDAV server base class, needs to be extended to do useful work
 *
 * @package FDL
 * @author  Hartmut Holzgraefe <hholzgra@php.net>
 * @version @package_version@
 */
/**
 */
//
// +----------------------------------------------------------------------+
// | PHP Version 4                                                        |
// +----------------------------------------------------------------------+
// | Copyright (c) 1997-2003 The PHP Group                                |
// +----------------------------------------------------------------------+
// | This source file is subject to version 2.02 of the PHP license,      |
// | that is bundled with this package in the file LICENSE, and is        |
// | available at through the world-wide-web at                           |
// | http://www.php.net/license/2_02.txt.                                 |
// | If you did not receive a copy of the PHP license and are unable to   |
// | obtain it through the world-wide-web, please send a note to          |
// | license@php.net so we can mail you a copy immediately.               |
// +----------------------------------------------------------------------+
// | Authors: Hartmut Holzgraefe <hholzgra@php.net>                       |
// |          Christian Stocker <chregu@bitflux.ch>                       |
// +----------------------------------------------------------------------+
//
// $Id: Class.ServerDav.php,v 1.8 2006/11/22 10:33:59 eric Exp $
//
require_once "DAV/_parse_propfind.php";
require_once "DAV/_parse_proppatch.php";
require_once "DAV/_parse_lockinfo.php";

class HTTP_WebDAV_Server
{
    /**
     * @var bool set to true to see xml response in error_log
     */
    public $debug = false;
    // {{{ Member Variables
    
    /**
     * complete URI for this request
     *
     * @var string
     */
    var $uri;
    /**
     * base URI for this request
     *
     * @var string
     */
    var $base_uri;
    /**
     * URI path for this request
     *
     * @var string
     */
    var $path;
    /**
     * Realm string to be used in authentification popups
     *
     * @var string
     */
    var $http_auth_realm = "PHP WebDAV";
    /**
     * String to be used in "X-Dav-Powered-By" header
     *
     * @var string
     */
    var $dav_powered_by = "";
    /**
     * Remember parsed If: (RFC2518/9.4) header conditions
     *
     * @var array
     */
    var $_if_header_uris = array();
    /**
     * HTTP response status/message
     *
     * @var string
     */
    var $_http_status = "200 OK";
    /**
     * encoding of property values passed in
     *
     * @var string
     */
    var $_prop_encoding = "utf-8";
    /**
     * Copy of $_SERVER superglobal array
     *
     * Derived classes may extend the constructor to
     * modify its contents
     *
     * @var array
     */
    var $_SERVER;
    // }}}
    // {{{ Constructor
    
    /** 
     * Constructor
     *
     * @param void
     */
    function __construct()
    {
        // PHP messages destroy XML output -> switch them off
        ini_set("display_errors", 0);
        // copy $_SERVER variables to local _SERVER array
        // so that derived classes can simply modify these
        $this->_SERVER = $_SERVER;
    }
    // }}}
    // {{{ ServeRequest()
    
    /** 
     * Serve WebDAV HTTP request
     *
     * dispatch WebDAV HTTP request to the apropriate method handler
     *
     * @param  void
     * @return void
     */
    function ServeRequest()
    {
        // prevent warning in litmus check 'delete_fragment'
        if (strstr($this->_SERVER["REQUEST_URI"], '#')) {
            $this->http_status("400 Bad Request");
            return;
        }
        // default uri is the complete request uri
        $uri = (@$this->_SERVER["HTTPS"] === "on" ? "https:" : "http:");
        $uri.= sprintf("//%s%s", $this->_SERVER["HTTP_HOST"], $this->_SERVER["SCRIPT_NAME"]);
        
        $path_info = empty($this->_SERVER["PATH_INFO"]) ? "/" : $this->_SERVER["PATH_INFO"];
        
        $this->base_uri = $uri;
        $this->uri = $uri . $path_info;
        // set path
        $this->path = $this->_urldecode($path_info);
        if (!strlen($this->path)) {
            if ($this->_SERVER["REQUEST_METHOD"] == "GET") {
                // redirect clients that try to GET a collection
                // WebDAV clients should never try this while
                // regular HTTP clients might ...
                header("Location: " . $this->base_uri . "/");
                return;
            } else {
                // if a WebDAV client didn't give a path we just assume '/'
                $this->path = "/";
            }
        }
        
        if (ini_get("magic_quotes_gpc")) {
            $this->path = stripslashes($this->path);
        }
        // identify ourselves
        if (empty($this->dav_powered_by)) {
            header("X-Dav-Powered-By: PHP class: " . get_class($this));
        } else {
            header("X-Dav-Powered-By: " . $this->dav_powered_by);
        }
        // check authentication
        // for the motivation for not checking OPTIONS requests on / see
        // http://pear.php.net/bugs/bug.php?id=5363
        if ((!(($this->_SERVER['REQUEST_METHOD'] == 'OPTIONS') && ($this->path == "/"))) && (!$this->_check_auth())) {
            // RFC2518 says we must use Digest instead of Basic
            // but Microsoft Clients do not support Digest
            // and we don't support NTLM and Kerberos
            // so we are stuck with Basic here
            header('WWW-Authenticate: Basic realm="' . ($this->http_auth_realm) . '"');
            // Windows seems to require this being the last header sent
            // (changed according to PECL bug #3138)
            $this->http_status('401 Unauthorized');
            
            return;
        }
        // check
        if (!$this->_check_if_header_conditions()) {
            return;
        }
        // detect requested method names
        $method = strtolower($this->_SERVER["REQUEST_METHOD"]);
        $wrapper = "http_" . $method;
        // activate HEAD emulation by GET if no HEAD method found
        if ($method == "head" && !method_exists($this, "head")) {
            $method = "get";
        }
        
        if (method_exists($this, $wrapper) && ($method == "options" || method_exists($this, $method))) {
            if ($this->debug) {
                ob_start();
                $this->$wrapper(); // call method by name
                $this->logContents();
                ob_end_flush();
            } else {
                $this->$wrapper(); // call method by name
                
            }
        } else { // method not found/implemented
            if ($this->_SERVER["REQUEST_METHOD"] == "LOCK") {
                $this->http_status("412 Precondition failed");
            } else {
                $this->http_status("405 Method not allowed");
                header("Allow: " . join(", ", $this->_allow())); // tell client what's allowed
                
            }
        }
    }
    
    private function logContents()
    {
        $a = ob_get_contents();
        if (substr($a, 0, 5) == '<?xml') {
            $c = explode("\n", $a);
            foreach ($c as $s) {
                error_log($s);
            }
        }
    }
    /**
     * OPTIONS method handler
     *
     * The OPTIONS method handler creates a valid OPTIONS reply
     * including Dav: and Allowed: heaers
     * based on the implemented methods found in the actual instance
     *
     * @param  void
     * @return void
     */
    function http_OPTIONS()
    {
        // Microsoft clients default to the Frontpage protocol
        // unless we tell them to use WebDAV
        header("MS-Author-Via: DAV");
        // get allowed methods
        $allow = $this->_allow();
        // dav header
        $dav = array(
            1
        ); // assume we are always dav class 1 compliant
        if (isset($allow['LOCK'])) {
            $dav[] = 2; // dav class 2 requires that locking is supported
            
        }
        // tell clients what we found
        $this->http_status("200 OK");
        header("DAV: " . join(", ", $dav));
        header("Allow: " . join(", ", $allow));
        
        header("Content-length: 0");
    }
    // }}}
    // {{{ http_PROPFIND()
    
    /**
     * PROPFIND method handler
     *
     * @param  void
     * @return void
     */
    function http_PROPFIND()
    {
        $options = Array();
        $files = Array();
        
        $options["path"] = $this->path;
        // search depth from header (default is "infinity)
        if (isset($this->_SERVER['HTTP_DEPTH'])) {
            $options["depth"] = $this->_SERVER["HTTP_DEPTH"];
        } else {
            $options["depth"] = "infinity";
        }
        // analyze request payload
        $propinfo = new _parse_propfind("php://input");
        if (!$propinfo->success) {
            $this->http_status("400 Error");
            return;
        }
        $options['props'] = $propinfo->props;
        // call user handler
        if (!$this->PROPFIND($options, $files)) {
            $files = array(
                "files" => array()
            );
            if (method_exists($this, "checkLock")) {
                // is locked?
                $lock = $this->checkLock($this->path);
                
                if (is_array($lock) && count($lock)) {
                    $created = isset($lock['created']) ? $lock['created'] : time();
                    $modified = isset($lock['modified']) ? $lock['modified'] : time();
                    $files['files'][] = array(
                        "path" => $this->_slashify($this->path) ,
                        "props" => array(
                            $this->mkprop("displayname", $this->path) ,
                            $this->mkprop("creationdate", $created) ,
                            $this->mkprop("getlastmodified", $modified) ,
                            $this->mkprop("resourcetype", "") ,
                            $this->mkprop("getcontenttype", "") ,
                            $this->mkprop("getcontentlength", 0)
                        )
                    );
                }
            }
            
            if (empty($files['files'])) {
                $this->http_status("404 Not Found");
                return;
            }
        }
        // collect namespaces here
        $ns_hash = array();
        // Microsoft Clients need this special namespace for date and time values
        $ns_defs = "xmlns:ns0=\"urn:uuid:c2f41010-65b3-11d1-a29f-00aa00c14882/\"";
        // now we loop over all returned file entries
        foreach ($files["files"] as $filekey => $file) {
            // nothing to do if no properties were returend for a file
            if (!isset($file["props"]) || !is_array($file["props"])) {
                continue;
            }
            // now loop over all returned properties
            foreach ($file["props"] as $key => $prop) {
                // as a convenience feature we do not require that user handlers
                // restrict returned properties to the requested ones
                // here we strip all unrequested entries out of the response
                switch ($options['props']) {
                    case "all":
                        // nothing to remove
                        break;

                    case "names":
                        // only the names of all existing properties were requested
                        // so we remove all values
                        unset($files["files"][$filekey]["props"][$key]["val"]);
                        break;

                    default:
                        $found = false;
                        // search property name in requested properties
                        foreach ((array)$options["props"] as $reqprop) {
                            if ($reqprop["name"] == $prop["name"] && @$reqprop["xmlns"] == $prop["ns"]) {
                                $found = true;
                                break;
                            }
                        }
                        // unset property and continue with next one if not found/requested
                        if (!$found) {
                            $files["files"][$filekey]["props"][$key] = "";
                            continue(2);
                        }
                        break;
                }
                // namespace handling
                if (empty($prop["ns"])) continue; // no namespace
                $ns = $prop["ns"];
                if ($ns == "DAV:") continue; // default namespace
                if (isset($ns_hash[$ns])) continue; // already known
                // register namespace
                $ns_name = "ns" . (count($ns_hash) + 1);
                $ns_hash[$ns] = $ns_name;
                $ns_defs.= " xmlns:$ns_name=\"$ns\"";
            }
            // we also need to add empty entries for properties that were requested
            // but for which no values where returned by the user handler
            if (is_array($options['props'])) {
                foreach ($options["props"] as $reqprop) {
                    if ($reqprop['name'] == "") continue; // skip empty entries
                    $found = false;
                    // check if property exists in result
                    foreach ($file["props"] as $prop) {
                        if ($reqprop["name"] == $prop["name"] && @$reqprop["xmlns"] == $prop["ns"]) {
                            $found = true;
                            break;
                        }
                    }
                    
                    if (!$found) {
                        if ($reqprop["xmlns"] === "DAV:" && $reqprop["name"] === "lockdiscovery") {
                            // lockdiscovery is handled by the base class
                            $files["files"][$filekey]["props"][] = $this->mkprop("DAV:", "lockdiscovery", $this->lockdiscovery($files["files"][$filekey]['path']));
                        } else {
                            // add empty value for this property
                            $files["files"][$filekey]["noprops"][] = $this->mkprop($reqprop["xmlns"], $reqprop["name"], "");
                            // register property namespace if not known yet
                            if ($reqprop["xmlns"] != "DAV:" && !isset($ns_hash[$reqprop["xmlns"]])) {
                                $ns_name = "ns" . (count($ns_hash) + 1);
                                $ns_hash[$reqprop["xmlns"]] = $ns_name;
                                $ns_defs.= " xmlns:$ns_name=\"$reqprop[xmlns]\"";
                            }
                        }
                    }
                }
            }
        }
        // now we generate the reply header ...
        $this->http_status("207 Multi-Status");
        header('Content-Type: text/xml; charset="utf-8"');
        // ... and payload
        echo "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n";
        echo "<D:multistatus xmlns:D=\"DAV:\">\n";
        
        foreach ($files["files"] as $file) {
            // ignore empty or incomplete entries
            if (!is_array($file) || empty($file) || !isset($file["path"])) continue;
            $path = $file['path'];
            if (!is_string($path) || $path === "") continue;
            
            echo " <D:response $ns_defs>\n";
            /* TODO right now the user implementation has to make sure
             collections end in a slash, this should be done in here
             by checking the resource attribute */
            $href = $this->_mergePathes($this->_SERVER['SCRIPT_NAME'], $path);
            
            echo "  <D:href>" . $this->_urlencode($href) . "</D:href>\n";
            // report all found properties and their values (if any)
            if (isset($file["props"]) && is_array($file["props"])) {
                echo "   <D:propstat>\n";
                echo "    <D:prop>\n";
                
                foreach ($file["props"] as $key => $prop) {
                    
                    if (!is_array($prop)) continue;
                    if (!isset($prop["name"])) continue;
                    
                    if (!isset($prop["val"]) || $prop["val"] === "" || $prop["val"] === false) {
                        // empty properties (cannot use empty() for check as "0" is a legal value here)
                        if ($prop["ns"] == "DAV:") {
                            echo "     <D:$prop[name]/>\n";
                        } else if (!empty($prop["ns"])) {
                            echo "     <" . $ns_hash[$prop["ns"]] . ":$prop[name]/>\n";
                        } else {
                            echo "     <$prop[name] xmlns=\"\"/>";
                        }
                    } else if ($prop["ns"] == "DAV:") {
                        // some WebDAV properties need special treatment
                        switch ($prop["name"]) {
                            case "creationdate":
                                echo "     <D:creationdate ns0:dt=\"dateTime.tz\">" . gmdate("Y-m-d\\TH:i:s\\Z", $prop['val']) . "</D:creationdate>\n";
                                break;

                            case "getlastmodified":
                                echo "     <D:getlastmodified ns0:dt=\"dateTime.rfc1123\">" . gmdate("D, d M Y H:i:s ", $prop['val']) . "GMT</D:getlastmodified>\n";
                                break;

                            case "resourcetype":
                                echo "     <D:resourcetype><D:$prop[val]/></D:resourcetype>\n";
                                break;

                            case "supportedlock":
                                echo "     <D:supportedlock>$prop[val]</D:supportedlock>\n";
                                break;

                            case "lockdiscovery":
                                echo "     <D:lockdiscovery>\n";
                                echo $prop["val"];
                                echo "     </D:lockdiscovery>\n";
                                break;

                            default:
                                echo "     <D:$prop[name]>" . $this->_prop_encode(htmlspecialchars($prop['val'])) . "</D:$prop[name]>\n";
                                break;
                        }
                    } else {
                        // properties from namespaces != "DAV:" or without any namespace
                        if ($prop["ns"]) {
                            echo "     <" . $ns_hash[$prop["ns"]] . ":$prop[name]>" . $this->_prop_encode(htmlspecialchars($prop['val'])) . "</" . $ns_hash[$prop["ns"]] . ":$prop[name]>\n";
                        } else {
                            echo "     <$prop[name] xmlns=\"\">" . $this->_prop_encode(htmlspecialchars($prop['val'])) . "</$prop[name]>\n";
                        }
                    }
                }
                
                echo "   </D:prop>\n";
                echo "   <D:status>HTTP/1.1 200 OK</D:status>\n";
                echo "  </D:propstat>\n";
            }
            // now report all properties requested but not found
            if (isset($file["noprops"])) {
                echo "   <D:propstat>\n";
                echo "    <D:prop>\n";
                
                foreach ($file["noprops"] as $key => $prop) {
                    if ($prop["ns"] == "DAV:") {
                        echo "     <D:$prop[name]/>\n";
                    } else if ($prop["ns"] == "") {
                        echo "     <$prop[name] xmlns=\"\"/>\n";
                    } else {
                        echo "     <" . $ns_hash[$prop["ns"]] . ":$prop[name]/>\n";
                    }
                }
                
                echo "   </D:prop>\n";
                echo "   <D:status>HTTP/1.1 404 Not Found</D:status>\n";
                echo "  </D:propstat>\n";
            }
            
            echo " </D:response>\n";
        }
        
        echo "</D:multistatus>\n";
    }
    // }}}
    // {{{ http_PROPPATCH()
    
    /**
     * PROPPATCH method handler
     *
     * @param  void
     * @return void
     */
    function http_PROPPATCH()
    {
        if ($this->_check_lock_status($this->path)) {
            $options = Array();
            
            $options["path"] = $this->path;
            
            $propinfo = new _parse_proppatch("php://input");
            
            if (!$propinfo->success) {
                $this->http_status("400 Error");
                return;
            }
            
            $options['props'] = $propinfo->props;
            
            $responsedescr = $this->PROPPATCH($options);
            
            $this->http_status("207 Multi-Status");
            header('Content-Type: text/xml; charset="utf-8"');
            
            echo "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n";
            
            echo "<D:multistatus xmlns:D=\"DAV:\">\n";
            echo " <D:response>\n";
            echo "  <D:href>" . $this->_urlencode($this->_mergePathes($this->_SERVER["SCRIPT_NAME"], $this->path)) . "</D:href>\n";
            
            foreach ($options["props"] as $prop) {
                echo "   <D:propstat>\n";
                echo "    <D:prop><$prop[name] xmlns=\"$prop[ns]\"/></D:prop>\n";
                echo "    <D:status>HTTP/1.1 $prop[status]</D:status>\n";
                echo "   </D:propstat>\n";
            }
            
            if ($responsedescr) {
                echo "  <D:responsedescription>" . $this->_prop_encode(htmlspecialchars($responsedescr)) . "</D:responsedescription>\n";
            }
            
            echo " </D:response>\n";
            echo "</D:multistatus>\n";
        } else {
            $this->http_status("423 Locked");
        }
    }
    // }}}
    // {{{ http_MKCOL()
    
    /**
     * MKCOL method handler
     *
     * @param  void
     * @return void
     */
    function http_MKCOL()
    {
        $options = Array();
        
        $options["path"] = $this->path;
        
        $stat = $this->MKCOL($options);
        
        $this->http_status($stat);
    }
    // }}}
    // {{{ http_GET()
    
    /**
     * GET method handler
     *
     * @param void
     * @returns void
     */
    function http_GET()
    {
        // TODO check for invalid stream
        $options = Array();
        $options["path"] = $this->path;
        
        $this->_get_ranges($options);
        
        if (true === ($status = $this->GET($options))) {
            if (!headers_sent()) {
                $status = "200 OK";
                
                if (!isset($options['mimetype'])) {
                    $options['mimetype'] = "application/octet-stream";
                }
                header("Content-type: $options[mimetype]");
                
                if (isset($options['mtime'])) {
                    header("Last-modified:" . gmdate("D, d M Y H:i:s ", $options['mtime']) . "GMT");
                }
                
                if (isset($options['stream'])) {
                    // GET handler returned a stream
                    if (!empty($options['ranges']) && (0 === fseek($options['stream'], 0, SEEK_SET))) {
                        // partial request and stream is seekable
                        if (count($options['ranges']) === 1) {
                            $range = $options['ranges'][0];
                            
                            if (isset($range['start'])) {
                                fseek($options['stream'], $range['start'], SEEK_SET);
                                if (feof($options['stream'])) {
                                    $this->http_status("416 Requested range not satisfiable");
                                    return;
                                }
                                
                                if (isset($range['end'])) {
                                    $size = $range['end'] - $range['start'] + 1;
                                    $this->http_status("206 partial");
                                    header("Content-length: $size");
                                    header("Content-range: $range[start]-$range[end]/" . (isset($options['size']) ? $options['size'] : "*"));
                                    while ($size && !feof($options['stream'])) {
                                        $buffer = fread($options['stream'], 4096);
                                        $size-= strlen($buffer);
                                        echo $buffer;
                                    }
                                } else {
                                    $this->http_status("206 partial");
                                    if (isset($options['size'])) {
                                        header("Content-length: " . ($options['size'] - $range['start']));
                                        header("Content-range: " . $range['start'] . "-" . $range['end'] . "/" . (isset($options['size']) ? $options['size'] : "*"));
                                    }
                                    fpassthru($options['stream']);
                                }
                            } else {
                                header("Content-length: " . $range['last']);
                                fseek($options['stream'], -$range['last'], SEEK_END);
                                fpassthru($options['stream']);
                            }
                        } else {
                            $this->_multipart_byterange_header(); // init multipart
                            foreach ($options['ranges'] as $range) {
                                // TODO what if size unknown? 500?
                                if (isset($range['start'])) {
                                    $from = $range['start'];
                                    $to = !empty($range['end']) ? $range['end'] : $options['size'] - 1;
                                } else {
                                    $from = $options['size'] - $range['last'] - 1;
                                    $to = $options['size'] - 1;
                                }
                                $total = isset($options['size']) ? $options['size'] : "*";
                                $size = $to - $from + 1;
                                $this->_multipart_byterange_header($options['mimetype'], $from, $to, $total);
                                
                                fseek($options['stream'], $from, SEEK_SET);
                                while ($size && !feof($options['stream'])) {
                                    $buffer = fread($options['stream'], 4096);
                                    $size-= strlen($buffer);
                                    echo $buffer;
                                }
                            }
                            $this->_multipart_byterange_header(); // end multipart
                            
                        }
                    } else {
                        // normal request or stream isn't seekable, return full content
                        if (isset($options['size'])) {
                            header("Content-length: " . $options['size']);
                        }
                        fpassthru($options['stream']);
                        return; // no more headers
                        
                    }
                } elseif (isset($options['data'])) {
                    if (is_array($options['data'])) {
                        // reply to partial request
                        
                    } else {
                        header("Content-length: " . strlen($options['data']));
                        echo $options['data'];
                    }
                }
            }
        }
        
        if (!headers_sent()) {
            if (false === $status) {
                $this->http_status("404 not found");
            } else {
                // TODO: check setting of headers in various code pathes above
                $this->http_status("$status");
            }
        }
    }
    /**
     * parse HTTP Range: header
     *
     * @param  array options array to store result in
     * @return void
     */
    function _get_ranges(&$options)
    {
        // process Range: header if present
        if (isset($this->_SERVER['HTTP_RANGE'])) {
            // we only support standard "bytes" range specifications for now
            if (preg_match('/bytes\s*=\s*(.+)/', $this->_SERVER['HTTP_RANGE'], $matches)) {
                $options["ranges"] = array();
                // ranges are comma separated
                foreach (explode(",", $matches[1]) as $range) {
                    // ranges are either from-to pairs or just end positions
                    list($start, $end) = explode("-", $range);
                    $options["ranges"][] = ($start === "") ? array(
                        "last" => $end
                    ) : array(
                        "start" => $start,
                        "end" => $end
                    );
                }
            }
        }
    }
    /**
     * generate separator headers for multipart response
     *
     * first and last call happen without parameters to generate
     * the initial header and closing sequence, all calls inbetween
     * require content mimetype, start and end byte position and
     * optionaly the total byte length of the requested resource
     *
     * @param  string  mimetype
     * @param  int     start byte position
     * @param  int     end   byte position
     * @param  int     total resource byte size
     */
    function _multipart_byterange_header($mimetype = false, $from = false, $to = false, $total = false)
    {
        if ($mimetype === false) {
            if (!isset($this->multipart_separator)) {
                // initial
                // a little naive, this sequence *might* be part of the content
                // but it's really not likely and rather expensive to check
                $this->multipart_separator = "SEPARATOR_" . md5(microtime());
                // generate HTTP header
                header("Content-type: multipart/byteranges; boundary=" . $this->multipart_separator);
            } else {
                // final
                // generate closing multipart sequence
                echo "\n--{$this->multipart_separator}--";
            }
        } else {
            // generate separator and header for next part
            echo "\n--{$this->multipart_separator}\n";
            echo "Content-type: $mimetype\n";
            echo "Content-range: $from-$to/" . ($total === false ? "*" : $total);
            echo "\n\n";
        }
    }
    // }}}
    // {{{ http_HEAD()
    
    /**
     * HEAD method handler
     *
     * @param  void
     * @return void
     */
    function http_HEAD()
    {
        $status = false;
        $options = Array();
        $options["path"] = $this->path;
        
        if (method_exists($this, "HEAD")) {
            $status = $this->head($options);
        } else if (method_exists($this, "GET")) {
            ob_start();
            $status = $this->GET($options);
            if (!isset($options['size'])) {
                $options['size'] = ob_get_length();
            }
            ob_end_clean();
        }
        
        if (!isset($options['mimetype'])) {
            $options['mimetype'] = "application/octet-stream";
        }
        header("Content-type: $options[mimetype]");
        
        if (isset($options['mtime'])) {
            header("Last-modified:" . gmdate("D, d M Y H:i:s ", $options['mtime']) . "GMT");
        }
        
        if (isset($options['size'])) {
            header("Content-length: " . $options['size']);
        }
        
        if ($status === true) $status = "200 OK";
        if ($status === false) $status = "404 Not found";
        
        $this->http_status($status);
    }
    // }}}
    // {{{ http_PUT()
    
    /**
     * PUT method handler
     *
     * @param  void
     * @return void
     */
    function http_PUT()
    {
        if ($this->_check_lock_status($this->path)) {
            $options = Array();
            $options["path"] = $this->path;
            $options["content_length"] = $this->_SERVER["CONTENT_LENGTH"];
            // get the Content-type
            if (isset($this->_SERVER["CONTENT_TYPE"])) {
                // for now we do not support any sort of multipart requests
                if (!strncmp($this->_SERVER["CONTENT_TYPE"], "multipart/", 10)) {
                    $this->http_status("501 not implemented");
                    echo "The service does not support mulipart PUT requests";
                    return;
                }
                $options["content_type"] = $this->_SERVER["CONTENT_TYPE"];
            } else {
                // default content type if none given
                $options["content_type"] = "application/octet-stream";
            }
            /* RFC 2616 2.6 says: "The recipient of the entity MUST NOT
             ignore any Content-* (e.g. Content-Range) headers that it 
             does not understand or implement and MUST return a 501 
             (Not Implemented) response in such cases."
            */
            foreach ($this->_SERVER as $key => $val) {
                if (strncmp($key, "HTTP_CONTENT", 11)) continue;
                switch ($key) {
                    case 'HTTP_CONTENT_ENCODING': // RFC 2616 14.11
                        // TODO support this if ext/zlib filters are available
                        $this->http_status("501 not implemented");
                        echo "The service does not support '$val' content encoding";
                        return;
                    case 'HTTP_CONTENT_LANGUAGE': // RFC 2616 14.12
                        // we assume it is not critical if this one is ignored
                        // in the actual PUT implementation ...
                        $options["content_language"] = $val;
                        break;

                    case 'HTTP_CONTENT_LOCATION': // RFC 2616 14.14
                        /* The meaning of the Content-Location header in PUT
                        or POST requests is undefined; servers are free
                        to ignore it in those cases. */
                        break;

                    case 'HTTP_CONTENT_RANGE': // RFC 2616 14.16
                        // single byte range requests are supported
                        // the header format is also specified in RFC 2616 14.16
                        // TODO we have to ensure that implementations support this or send 501 instead
                        if (!preg_match('@bytes\s+(\d+)-(\d+)/((\d+)|\*)@', $val, $matches)) {
                            $this->http_status("400 bad request");
                            echo "The service does only support single byte ranges";
                            return;
                        }
                        
                        $range = array(
                            "start" => $matches[1],
                            "end" => $matches[2]
                        );
                        if (is_numeric($matches[3])) {
                            $range["total_length"] = $matches[3];
                        }
                        $option["ranges"][] = $range;
                        // TODO make sure the implementation supports partial PUT
                        // this has to be done in advance to avoid data being overwritten
                        // on implementations that do not support this ...
                        break;

                    case 'HTTP_CONTENT_MD5': // RFC 2616 14.15
                        // TODO: maybe we can just pretend here?
                        $this->http_status("501 not implemented");
                        echo "The service does not support content MD5 checksum verification";
                        return;
                    default:
                        // any other unknown Content-* headers
                        $this->http_status("501 not implemented");
                        echo "The service does not support '$key'";
                        return;
                }
            }
            
            $options["stream"] = fopen("php://input", "r");
            
            $stat = $this->PUT($options);
            
            if ($stat === false) {
                $stat = "403 Forbidden";
            } else if (is_resource($stat) && get_resource_type($stat) == "stream") {
                $stream = $stat;
                
                $stat = $options["new"] ? "201 Created" : "204 No Content";
                
                if (!empty($options["ranges"])) {
                    // TODO multipart support is missing (see also above)
                    if (0 == fseek($stream, $range[0]["start"], SEEK_SET)) {
                        $length = $range[0]["end"] - $range[0]["start"] + 1;
                        if (!fwrite($stream, fread($options["stream"], $length))) {
                            $stat = "403 Forbidden";
                        }
                    } else {
                        $stat = "403 Forbidden";
                    }
                } else {
                    while (!feof($options["stream"])) {
                        if (false === fwrite($stream, fread($options["stream"], 4096))) {
                            $stat = "403 Forbidden";
                            break;
                        }
                    }
                }
                
                fclose($stream);
            }
            
            $this->http_status($stat);
        } else {
            $this->http_status("423 Locked");
        }
    }
    // }}}
    // {{{ http_DELETE()
    
    /**
     * DELETE method handler
     *
     * @param  void
     * @return void
     */
    function http_DELETE()
    {
        // check RFC 2518 Section 9.2, last paragraph
        if (isset($this->_SERVER["HTTP_DEPTH"])) {
            if ($this->_SERVER["HTTP_DEPTH"] != "infinity") {
                $this->http_status("400 Bad Request");
                return;
            }
        }
        // check lock status
        if ($this->_check_lock_status($this->path)) {
            // ok, proceed
            $options = Array();
            $options["path"] = $this->path;
            
            $stat = $this->DELETE($options);
            
            $this->http_status($stat);
        } else {
            // sorry, its locked
            $this->http_status("423 Locked");
        }
    }
    // }}}
    // {{{ http_COPY()
    
    /**
     * COPY method handler
     *
     * @param  void
     * @return void
     */
    function http_COPY()
    {
        // no need to check source lock status here
        // destination lock status is always checked by the helper method
        $this->_copymove("copy");
    }
    // }}}
    // {{{ http_MOVE()
    
    /**
     * MOVE method handler
     *
     * @param  void
     * @return void
     */
    function http_MOVE()
    {
        if ($this->_check_lock_status($this->path)) {
            // destination lock status is always checked by the helper method
            $this->_copymove("move");
        } else {
            $this->http_status("423 Locked");
        }
    }
    // }}}
    // {{{ http_LOCK()
    
    /**
     * LOCK method handler
     *
     * @param  void
     * @return void
     */
    function http_LOCK()
    {
        $options = Array();
        $options["path"] = $this->path;
        
        if (isset($this->_SERVER['HTTP_DEPTH'])) {
            $options["depth"] = $this->_SERVER["HTTP_DEPTH"];
        } else {
            $options["depth"] = "infinity";
        }
        
        if (isset($this->_SERVER["HTTP_TIMEOUT"])) {
            $options["timeout"] = explode(",", $this->_SERVER["HTTP_TIMEOUT"]);
        }
        
        if (empty($this->_SERVER['CONTENT_LENGTH']) && !empty($this->_SERVER['HTTP_IF'])) {
            // check if locking is possible
            if (!$this->_check_lock_status($this->path)) {
                $this->http_status("423 Locked");
                return;
            }
            // refresh lock
            $options["locktoken"] = substr($this->_SERVER['HTTP_IF'], 2, -2);
            $options["update"] = $options["locktoken"];
            // setting defaults for required fields, LOCK() SHOULD overwrite these
            $options['owner'] = "unknown";
            $options['scope'] = "exclusive";
            $options['type'] = "write";
            
            $stat = $this->LOCK($options);
        } else {
            // extract lock request information from request XML payload
            $lockinfo = new _parse_lockinfo("php://input");
            if (!$lockinfo->success) {
                $this->http_status("400 bad request");
            }
            // check if locking is possible
            if (!$this->_check_lock_status($this->path, $lockinfo->lockscope === "shared")) {
                $this->http_status("423 Locked");
                return;
            }
            // new lock
            $options["scope"] = $lockinfo->lockscope;
            $options["type"] = $lockinfo->locktype;
            $options["owner"] = $lockinfo->owner;
            $options["locktoken"] = $this->_new_locktoken();
            
            $stat = $this->LOCK($options);
        }
        
        if (is_bool($stat)) {
            $http_stat = $stat ? "200 OK" : "423 Locked";
        } else {
            $http_stat = $stat;
        }
        $this->http_status($http_stat);
        
        if ($http_stat{0} == 2) { // 2xx states are ok
            if ($options["timeout"]) {
                // more than a million is considered an absolute timestamp
                // less is more likely a relative value
                if ($options["timeout"] > 1000000) {
                    $timeout = "Second-" . ($options['timeout'] - time());
                } else {
                    $timeout = "Second-$options[timeout]";
                }
            } else {
                $timeout = "Infinite";
            }
            
            header('Content-Type: text/xml; charset="utf-8"');
            header("Lock-Token: <$options[locktoken]>");
            echo "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n";
            echo "<D:prop xmlns:D=\"DAV:\">\n";
            echo " <D:lockdiscovery>\n";
            echo "  <D:activelock>\n";
            echo "   <D:lockscope><D:$options[scope]/></D:lockscope>\n";
            echo "   <D:locktype><D:$options[type]/></D:locktype>\n";
            echo "   <D:depth>$options[depth]</D:depth>\n";
            echo "   <D:owner>$options[owner]</D:owner>\n";
            echo "   <D:timeout>$timeout</D:timeout>\n";
            echo "   <D:locktoken><D:href>$options[locktoken]</D:href></D:locktoken>\n";
            echo "  </D:activelock>\n";
            echo " </D:lockdiscovery>\n";
            echo "</D:prop>\n\n";
        }
    }
    // }}}
    // {{{ http_UNLOCK()
    
    /**
     * UNLOCK method handler
     *
     * @param  void
     * @return void
     */
    function http_UNLOCK()
    {
        $options = Array();
        $options["path"] = $this->path;
        
        if (isset($this->_SERVER['HTTP_DEPTH'])) {
            $options["depth"] = $this->_SERVER["HTTP_DEPTH"];
        } else {
            $options["depth"] = "infinity";
        }
        // strip surrounding <>
        $options["token"] = trim($this->_SERVER["HTTP_LOCK_TOKEN"], '<> ');
        // call user method
        $stat = $this->UNLOCK($options);
        
        $this->http_status($stat);
    }
    // }}}
    // }}}
    // {{{ _copymove()
    function _copymove($what)
    {
        $options = Array();
        $options["path"] = $this->path;
        
        if (isset($this->_SERVER["HTTP_DEPTH"])) {
            $options["depth"] = $this->_SERVER["HTTP_DEPTH"];
        } else {
            $options["depth"] = "infinity";
        }
        
        $urlInfo = parse_url($this->_SERVER["HTTP_DESTINATION"]);
        $path = str_replace("%25", "%", $urlInfo["path"]);
        $path = urldecode($path);
        $http_host = $urlInfo["host"];
        if (isset($port) && $port != 80) $http_host.= ":$port";
        
        $http_header_host = preg_replace("/:80$/", "", $this->_SERVER["HTTP_HOST"]);
        
        $basepath = dirname($_SERVER["PHP_SELF"]);
        if ($http_host == $http_header_host
        /*      !strncmp($_SERVER["SCRIPT_NAME"], $path,
         strlen($this->__SERVER["SCRIPT_NAME"]))*/) {
            //                  $options["dest"] = substr($path, strlen($this->__SERVER["SCRIPT_NAME"]));
            if (strlen($basepath) > 1) {
                $path = substr($path, strlen($basepath));
            }
            $options["dest"] = $path;
            
            if (!$this->_check_lock_status($options["dest"])) {
                $this->http_status("423 Locked");
                return;
            }
        } else {
            $options["dest_url"] = $this->_SERVER["HTTP_DESTINATION"];
        }
        // see RFC 2518 Sections 9.6, 8.8.4 and 8.9.3
        if (isset($this->_SERVER["HTTP_OVERWRITE"])) {
            $options["overwrite"] = $this->_SERVER["HTTP_OVERWRITE"] == "T";
        } else {
            $options["overwrite"] = true;
        }
        
        $stat = $this->$what($options);
        $this->http_status($stat);
    }
    // }}}
    // {{{ _allow()
    
    /**
     * check for implemented HTTP methods
     *
     * @param  void
     * @return array something
     */
    function _allow()
    {
        // OPTIONS is always there
        $allow = array(
            "OPTIONS" => "OPTIONS"
        );
        // all other METHODS need both a http_method() wrapper
        // and a method() implementation
        // the base class supplies wrappers only
        foreach (get_class_methods($this) as $method) {
            if (!strncmp("http_", $method, 5)) {
                $method = strtoupper(substr($method, 5));
                if (method_exists($this, $method)) {
                    $allow[$method] = $method;
                }
            }
        }
        // we can emulate a missing HEAD implemetation using GET
        if (isset($allow["GET"])) $allow["HEAD"] = "HEAD";
        // no LOCK without checklok()
        if (!method_exists($this, "checklock")) {
            unset($allow["LOCK"]);
            unset($allow["UNLOCK"]);
        }
        
        return $allow;
    }
    // }}}
    
    /**
     * helper for property element creation
     *
     * @param  string  XML namespace (optional)
     * @param  string  property name
     * @param  string  property value
     * @return array   property array
     */
    function mkprop()
    {
        $args = func_get_args();
        if (count($args) == 3) {
            return array(
                "ns" => $args[0],
                "name" => $args[1],
                "val" => $args[2]
            );
        } else {
            return array(
                "ns" => "DAV:",
                "name" => $args[0],
                "val" => $args[1]
            );
        }
    }
    // {{{ _check_auth
    
    /**
     * check authentication if check is implemented
     *
     * @param  void
     * @return bool  true if authentication succeded or not necessary
     */
    function _check_auth()
    {
        if (method_exists($this, "checkAuth")) {
            // PEAR style method name
            return $this->checkAuth(@$this->_SERVER["AUTH_TYPE"], @$this->_SERVER["PHP_AUTH_USER"], @$this->_SERVER["PHP_AUTH_PW"]);
        } else if (method_exists($this, "check_auth")) {
            // old (pre 1.0) method name
            return $this->check_auth(@$this->_SERVER["AUTH_TYPE"], @$this->_SERVER["PHP_AUTH_USER"], @$this->_SERVER["PHP_AUTH_PW"]);
        } else {
            // no method found -> no authentication required
            return true;
        }
    }
    // }}}
    // {{{ UUID stuff
    
    /**
     * generate Unique Universal IDentifier for lock token
     *
     * @param  void
     * @return string  a new UUID
     */
    function _new_uuid()
    {
        // use uuid extension from PECL if available
        if (function_exists("uuid_create")) {
            return uuid_create();
        }
        // fallback
        $uuid = md5(microtime() . getmypid()); // this should be random enough for now
        // set variant and version fields for 'true' random uuid
        $uuid{12} = "4";
        $n = 8 + (ord($uuid{16}) & 3);
        $hex = "0123456789abcdef";
        $uuid{16} = $hex{$n};
        // return formated uuid
        return substr($uuid, 0, 8) . "-" . substr($uuid, 8, 4) . "-" . substr($uuid, 12, 4) . "-" . substr($uuid, 16, 4) . "-" . substr($uuid, 20);
    }
    /**
     * create a new opaque lock token as defined in RFC2518
     *
     * @param  void
     * @return string  new RFC2518 opaque lock token
     */
    function _new_locktoken()
    {
        return "opaquelocktoken:" . $this->_new_uuid();
    }
    // }}}
    // {{{ WebDAV If: header parsing
    
    /**
     *
     *
     * @param  string  $string header string to parse
     * @param  int     $pos current parsing position
     * @return array|false   next token (type and value)
     */
    function _if_header_lexer($string, &$pos)
    {
        // skip whitespace
        while (ctype_space($string{$pos})) {
            ++$pos;
        }
        // already at end of string?
        if (strlen($string) <= $pos) {
            return false;
        }
        // get next character
        $c = $string{$pos++};
        // now it depends on what we found
        switch ($c) {
            case "<":
                // URIs are enclosed in <...>
                $pos2 = strpos($string, ">", $pos);
                $uri = substr($string, $pos, $pos2 - $pos);
                $pos = $pos2 + 1;
                return array(
                    "URI",
                    $uri
                );
            case "[":
                //Etags are enclosed in [...]
                if ($string{$pos} == "W") {
                    $type = "ETAG_WEAK";
                    $pos+= 2;
                } else {
                    $type = "ETAG_STRONG";
                }
                $pos2 = strpos($string, "]", $pos);
                $etag = substr($string, $pos + 1, $pos2 - $pos - 2);
                $pos = $pos2 + 1;
                return array(
                    $type,
                    $etag
                );
            case "N":
                // "N" indicates negation
                $pos+= 2;
                return array(
                    "NOT",
                    "Not"
                );
            default:
                // anything else is passed verbatim char by char
                return array(
                    "CHAR",
                    $c
                );
        }
    }
    /** 
     * parse If: header
     *
     * @param  string  header string
     * @return array|bool   URIs and their conditions
     */
    function _if_header_parser($str)
    {
        $pos = 0;
        $len = strlen($str);
        $uris = array();
        // parser loop
        while ($pos < $len) {
            // get next token
            $token = $this->_if_header_lexer($str, $pos);
            // check for URI
            if ($token[0] == "URI") {
                $uri = $token[1]; // remember URI
                $token = $this->_if_header_lexer($str, $pos); // get next token
                
            } else {
                $uri = "";
            }
            // sanity check
            if ($token[0] != "CHAR" || $token[1] != "(") {
                return false;
            }
            
            $list = array();
            $level = 1;
            $not = "";
            while ($level) {
                $token = $this->_if_header_lexer($str, $pos);
                if ($token[0] == "NOT") {
                    $not = "!";
                    continue;
                }
                switch ($token[0]) {
                    case "CHAR":
                        switch ($token[1]) {
                            case "(":
                                $level++;
                                break;

                            case ")":
                                $level--;
                                break;

                            default:
                                return false;
                        }
                        break;

                    case "URI":
                        $list[] = $not . "<$token[1]>";
                        break;

                    case "ETAG_WEAK":
                        $list[] = $not . "[W/'$token[1]']>";
                        break;

                    case "ETAG_STRONG":
                        $list[] = $not . "['$token[1]']>";
                        break;

                    default:
                        return false;
                }
                $not = "";
            }
            
            if (@is_array($uris[$uri])) {
                $uris[$uri] = array_merge($uris[$uri], $list);
            } else {
                $uris[$uri] = $list;
            }
        }
        
        return $uris;
    }
    /**
     * check if conditions from "If:" headers are meat
     *
     * the "If:" header is an extension to HTTP/1.1
     * defined in RFC 2518 section 9.4
     *
     * @param  void
     * @return string
     */
    function _check_if_header_conditions()
    {
        if (isset($this->_SERVER["HTTP_IF"])) {
            $this->_if_header_uris = $this->_if_header_parser($this->_SERVER["HTTP_IF"]);
            
            foreach ($this->_if_header_uris as $uri => $conditions) {
                if ($uri == "") {
                    $uri = $this->uri;
                }
                // all must match
                $state = true;
                foreach ($conditions as $condition) {
                    // lock tokens may be free form (RFC2518 6.3)
                    // but if opaquelocktokens are used (RFC2518 6.4)
                    // we have to check the format (litmus tests this)
                    if (!strncmp($condition, "<opaquelocktoken:", strlen("<opaquelocktoken"))) {
                        if (!preg_match('/^<opaquelocktoken:[[:xdigit:]]{8}-[[:xdigit:]]{4}-[[:xdigit:]]{4}-[[:xdigit:]]{4}-[[:xdigit:]]{12}>$/', $condition)) {
                            $this->http_status("423 Locked");
                            return false;
                        }
                    }
                    if (!$this->_check_uri_condition($uri, $condition)) {
                        $this->http_status("412 Precondition failed");
                        $state = false;
                        break;
                    }
                }
                // any match is ok
                if ($state == true) {
                    return true;
                }
            }
            return false;
        }
        return true;
    }
    /**
     * Check a single URI condition parsed from an if-header
     *
     * Check a single URI condition parsed from an if-header
     *
     * @abstract
     * @param string $uri URI to check
     * @param string $condition Condition to check for this URI
     * @returns bool Condition check result
     */
    function _check_uri_condition($uri, $condition)
    {
        // not really implemented here,
        // implementations must override
        // a lock token can never be from the DAV: scheme
        // litmus uses DAV:no-lock in some tests
        if (!strncmp("<DAV:", $condition, 5)) {
            return false;
        }
        
        return true;
    }
    /**
     *
     *
     * @param  string  path of resource to check
     * @param  bool    exclusive lock?
     */
    function _check_lock_status($path, $exclusive_only = false)
    {
        // FIXME depth -> ignored for now
        if (method_exists($this, "checkLock")) {
            // is locked?
            $lock = $this->checkLock($path);
            // ... and lock is not owned?
            if (is_array($lock) && count($lock)) {
                // FIXME doesn't check uri restrictions yet
                if (!isset($this->_SERVER["HTTP_IF"]) || !strstr($this->_SERVER["HTTP_IF"], $lock["token"])) {
                    if (!$exclusive_only || ($lock["scope"] !== "shared")) return false;
                }
            }
        }
        return true;
    }
    // }}}
    
    
    /**
     * Generate lockdiscovery reply from checklock() result
     *
     * @param   string  resource path to check
     * @return  string  lockdiscovery response
     */
    function lockdiscovery($path)
    {
        // no lock support without checklock() method
        if (!method_exists($this, "checklock")) {
            return "";
        }
        // collect response here
        $activelocks = "";
        // get checklock() reply
        $lock = $this->checklock($path);
        // generate <activelock> block for returned data
        if (is_array($lock) && count($lock)) {
            // check for 'timeout' or 'expires'
            if (!empty($lock["expires"])) {
                $timeout = "Second-" . ($lock["expires"] - time());
            } else if (!empty($lock["timeout"])) {
                $timeout = "Second-$lock[timeout]";
            } else {
                $timeout = "Infinite";
            }
            // genreate response block
            $activelocks.= "
              <D:activelock>
               <D:lockscope><D:$lock[scope]/></D:lockscope>
               <D:locktype><D:$lock[type]/></D:locktype>
               <D:depth>$lock[depth]</D:depth>
               <D:owner>$lock[owner]</D:owner>
               <D:timeout>$timeout</D:timeout>
               <D:locktoken><D:href>$lock[token]</D:href></D:locktoken>
              </D:activelock>
             ";
        }
        // return generated response
        return $activelocks;
    }
    /**
     * set HTTP return status and mirror it in a private header
     *
     * @param  string  status code and message
     * @return void
     */
    function http_status($status)
    {
        // simplified success case
        if ($status === true) {
            $status = "200 OK";
        }
        // remember status
        $this->_http_status = $status;
        // generate HTTP status response
        header("HTTP/1.1 $status");
        header("X-WebDAV-Status: $status", true);
    }
    /**
     * private minimalistic version of PHP urlencode()
     *
     * only blanks and XML special chars must be encoded here
     * full urlencode() encoding confuses some clients ...
     *
     * @param  string  URL to encode
     * @return string  encoded URL
     */
    function _urlencode($url)
    {
        $r = rawurlencode($url);
        return str_replace("%2F", "/", $r);
    }
    /**
     * private version of PHP urldecode
     *
     * not really needed but added for completenes
     *
     * @param  string  URL to decode
     * @return string  decoded URL
     */
    function _urldecode($path)
    {
        return urldecode($path);
    }
    /**
     * UTF-8 encode property values if not already done so
     *
     * @param  string  text to encode
     * @return string  utf-8 encoded text
     */
    function _prop_encode($text)
    {
        switch (strtolower($this->_prop_encoding)) {
            case "utf-8":
                return $text;
            case "iso-8859-1":
            case "iso-8859-15":
            case "latin-1":
            default:
                return utf8_encode($text);
        }
    }
    /**
     * Slashify - make sure path ends in a slash
     *
     * @param   string directory path
     * @returns string directory path wiht trailing slash
     */
    function _slashify($path)
    {
        if ($path[strlen($path) - 1] != '/') {
            $path = $path . "/";
        }
        return $path;
    }
    /**
     * Unslashify - make sure path doesn't in a slash
     *
     * @param   string directory path
     * @returns string directory path wihtout trailing slash
     */
    function _unslashify($path)
    {
        if ($path[strlen($path) - 1] == '/') {
            $path = substr($path, 0, -1);
        }
        return $path;
    }
    /**
     * Merge two pathes, make sure there is exactly one slash between them
     *
     * @param  string  $parent parent path
     * @param  string  $child child path
     * @return string  merged path
     */
    function _mergePathes($parent, $child)
    {
        if ($child{0} == '/') {
            return $this->_unslashify($parent) . $child;
        } else {
            return $this->_slashify($parent) . $child;
        }
    }
}