SFTP.php

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<?php

namespace phpseclib\Net;

use phpseclib\Net\SSH2;

class SFTP extends SSH2
{
    const CHANNEL = 0x100;

    const SOURCE_LOCAL_FILE = 1;
    // this value isn't really used anymore but i'm keeping it reserved for historical reasons
    const SOURCE_STRING = 2;
    const SOURCE_CALLBACK = 16;
    const RESUME = 4;
    const RESUME_START = 8;
    var $packet_types = array();

    var $status_codes = array();

    var $request_id = false;

    var $packet_type = -1;

    var $packet_buffer = '';

    var $extensions = array();

    var $version;

    var $pwd = false;

    var $packet_type_log = array();

    var $packet_log = array();

    var $sftp_errors = array();

    var $stat_cache = array();

    var $max_sftp_packet;

    var $use_stat_cache = true;

    var $sortOptions = array();

    function __construct($host, $port = 22, $timeout = 10)
    {
        parent::__construct($host, $port, $timeout);

        $this->max_sftp_packet = 1 << 15;

        $this->packet_types = array(
            1  => 'NET_SFTP_INIT',
            2  => 'NET_SFTP_VERSION',
            /* the format of SSH_FXP_OPEN changed between SFTPv4 and SFTPv5+:
                   SFTPv5+: http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.1.1
               pre-SFTPv5 : http://tools.ietf.org/html/draft-ietf-secsh-filexfer-04#section-6.3 */
            3  => 'NET_SFTP_OPEN',
            4  => 'NET_SFTP_CLOSE',
            5  => 'NET_SFTP_READ',
            6  => 'NET_SFTP_WRITE',
            7  => 'NET_SFTP_LSTAT',
            9  => 'NET_SFTP_SETSTAT',
            11 => 'NET_SFTP_OPENDIR',
            12 => 'NET_SFTP_READDIR',
            13 => 'NET_SFTP_REMOVE',
            14 => 'NET_SFTP_MKDIR',
            15 => 'NET_SFTP_RMDIR',
            16 => 'NET_SFTP_REALPATH',
            17 => 'NET_SFTP_STAT',
            /* the format of SSH_FXP_RENAME changed between SFTPv4 and SFTPv5+:
                   SFTPv5+: http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.3
               pre-SFTPv5 : http://tools.ietf.org/html/draft-ietf-secsh-filexfer-04#section-6.5 */
            18 => 'NET_SFTP_RENAME',
            19 => 'NET_SFTP_READLINK',
            20 => 'NET_SFTP_SYMLINK',

            101=> 'NET_SFTP_STATUS',
            102=> 'NET_SFTP_HANDLE',
            /* the format of SSH_FXP_NAME changed between SFTPv3 and SFTPv4+:
                   SFTPv4+: http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-9.4
               pre-SFTPv4 : http://tools.ietf.org/html/draft-ietf-secsh-filexfer-02#section-7 */
            103=> 'NET_SFTP_DATA',
            104=> 'NET_SFTP_NAME',
            105=> 'NET_SFTP_ATTRS',

            200=> 'NET_SFTP_EXTENDED'
        );
        $this->status_codes = array(
            0 => 'NET_SFTP_STATUS_OK',
            1 => 'NET_SFTP_STATUS_EOF',
            2 => 'NET_SFTP_STATUS_NO_SUCH_FILE',
            3 => 'NET_SFTP_STATUS_PERMISSION_DENIED',
            4 => 'NET_SFTP_STATUS_FAILURE',
            5 => 'NET_SFTP_STATUS_BAD_MESSAGE',
            6 => 'NET_SFTP_STATUS_NO_CONNECTION',
            7 => 'NET_SFTP_STATUS_CONNECTION_LOST',
            8 => 'NET_SFTP_STATUS_OP_UNSUPPORTED',
            9 => 'NET_SFTP_STATUS_INVALID_HANDLE',
            10 => 'NET_SFTP_STATUS_NO_SUCH_PATH',
            11 => 'NET_SFTP_STATUS_FILE_ALREADY_EXISTS',
            12 => 'NET_SFTP_STATUS_WRITE_PROTECT',
            13 => 'NET_SFTP_STATUS_NO_MEDIA',
            14 => 'NET_SFTP_STATUS_NO_SPACE_ON_FILESYSTEM',
            15 => 'NET_SFTP_STATUS_QUOTA_EXCEEDED',
            16 => 'NET_SFTP_STATUS_UNKNOWN_PRINCIPAL',
            17 => 'NET_SFTP_STATUS_LOCK_CONFLICT',
            18 => 'NET_SFTP_STATUS_DIR_NOT_EMPTY',
            19 => 'NET_SFTP_STATUS_NOT_A_DIRECTORY',
            20 => 'NET_SFTP_STATUS_INVALID_FILENAME',
            21 => 'NET_SFTP_STATUS_LINK_LOOP',
            22 => 'NET_SFTP_STATUS_CANNOT_DELETE',
            23 => 'NET_SFTP_STATUS_INVALID_PARAMETER',
            24 => 'NET_SFTP_STATUS_FILE_IS_A_DIRECTORY',
            25 => 'NET_SFTP_STATUS_BYTE_RANGE_LOCK_CONFLICT',
            26 => 'NET_SFTP_STATUS_BYTE_RANGE_LOCK_REFUSED',
            27 => 'NET_SFTP_STATUS_DELETE_PENDING',
            28 => 'NET_SFTP_STATUS_FILE_CORRUPT',
            29 => 'NET_SFTP_STATUS_OWNER_INVALID',
            30 => 'NET_SFTP_STATUS_GROUP_INVALID',
            31 => 'NET_SFTP_STATUS_NO_MATCHING_BYTE_RANGE_LOCK'
        );
        // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-7.1
        // the order, in this case, matters quite a lot - see \phpseclib\Net\SFTP::_parseAttributes() to understand why
        $this->attributes = array(
            0x00000001 => 'NET_SFTP_ATTR_SIZE',
            0x00000002 => 'NET_SFTP_ATTR_UIDGID', // defined in SFTPv3, removed in SFTPv4+
            0x00000004 => 'NET_SFTP_ATTR_PERMISSIONS',
            0x00000008 => 'NET_SFTP_ATTR_ACCESSTIME',
            // 0x80000000 will yield a floating point on 32-bit systems and converting floating points to integers
            // yields inconsistent behavior depending on how php is compiled.  so we left shift -1 (which, in
            // two's compliment, consists of all 1 bits) by 31.  on 64-bit systems this'll yield 0xFFFFFFFF80000000.
            // that's not a problem, however, and 'anded' and a 32-bit number, as all the leading 1 bits are ignored.
              -1 << 31 => 'NET_SFTP_ATTR_EXTENDED'
        );
        // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-04#section-6.3
        // the flag definitions change somewhat in SFTPv5+.  if SFTPv5+ support is added to this library, maybe name
        // the array for that $this->open5_flags and similarily alter the constant names.
        $this->open_flags = array(
            0x00000001 => 'NET_SFTP_OPEN_READ',
            0x00000002 => 'NET_SFTP_OPEN_WRITE',
            0x00000004 => 'NET_SFTP_OPEN_APPEND',
            0x00000008 => 'NET_SFTP_OPEN_CREATE',
            0x00000010 => 'NET_SFTP_OPEN_TRUNCATE',
            0x00000020 => 'NET_SFTP_OPEN_EXCL'
        );
        // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-04#section-5.2
        // see \phpseclib\Net\SFTP::_parseLongname() for an explanation
        $this->file_types = array(
            1 => 'NET_SFTP_TYPE_REGULAR',
            2 => 'NET_SFTP_TYPE_DIRECTORY',
            3 => 'NET_SFTP_TYPE_SYMLINK',
            4 => 'NET_SFTP_TYPE_SPECIAL',
            5 => 'NET_SFTP_TYPE_UNKNOWN',
            // the followin types were first defined for use in SFTPv5+
            // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-05#section-5.2
            6 => 'NET_SFTP_TYPE_SOCKET',
            7 => 'NET_SFTP_TYPE_CHAR_DEVICE',
            8 => 'NET_SFTP_TYPE_BLOCK_DEVICE',
            9 => 'NET_SFTP_TYPE_FIFO'
        );
        $this->_define_array(
            $this->packet_types,
            $this->status_codes,
            $this->attributes,
            $this->open_flags,
            $this->file_types
        );

        if (!defined('NET_SFTP_QUEUE_SIZE')) {
            define('NET_SFTP_QUEUE_SIZE', 50);
        }
    }

    function login($username)
    {
        $args = func_get_args();
        if (!call_user_func_array(array(&$this, '_login'), $args)) {
            return false;
        }

        $this->window_size_server_to_client[self::CHANNEL] = $this->window_size;

        $packet = pack(
            'CNa*N3',
            NET_SSH2_MSG_CHANNEL_OPEN,
            strlen('session'),
            'session',
            self::CHANNEL,
            $this->window_size,
            0x4000
        );

        if (!$this->_send_binary_packet($packet)) {
            return false;
        }

        $this->channel_status[self::CHANNEL] = NET_SSH2_MSG_CHANNEL_OPEN;

        $response = $this->_get_channel_packet(self::CHANNEL);
        if ($response === false) {
            return false;
        }

        $packet = pack(
            'CNNa*CNa*',
            NET_SSH2_MSG_CHANNEL_REQUEST,
            $this->server_channels[self::CHANNEL],
            strlen('subsystem'),
            'subsystem',
            1,
            strlen('sftp'),
            'sftp'
        );
        if (!$this->_send_binary_packet($packet)) {
            return false;
        }

        $this->channel_status[self::CHANNEL] = NET_SSH2_MSG_CHANNEL_REQUEST;

        $response = $this->_get_channel_packet(self::CHANNEL);
        if ($response === false) {
            // from PuTTY's psftp.exe
            $command = "test -x /usr/lib/sftp-server && exec /usr/lib/sftp-server\n" .
                       "test -x /usr/local/lib/sftp-server && exec /usr/local/lib/sftp-server\n" .
                       "exec sftp-server";
            // we don't do $this->exec($command, false) because exec() operates on a different channel and plus the SSH_MSG_CHANNEL_OPEN that exec() does
            // is redundant
            $packet = pack(
                'CNNa*CNa*',
                NET_SSH2_MSG_CHANNEL_REQUEST,
                $this->server_channels[self::CHANNEL],
                strlen('exec'),
                'exec',
                1,
                strlen($command),
                $command
            );
            if (!$this->_send_binary_packet($packet)) {
                return false;
            }

            $this->channel_status[self::CHANNEL] = NET_SSH2_MSG_CHANNEL_REQUEST;

            $response = $this->_get_channel_packet(self::CHANNEL);
            if ($response === false) {
                return false;
            }
        }

        $this->channel_status[self::CHANNEL] = NET_SSH2_MSG_CHANNEL_DATA;

        if (!$this->_send_sftp_packet(NET_SFTP_INIT, "\0\0\0\3")) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        if ($this->packet_type != NET_SFTP_VERSION) {
            user_error('Expected SSH_FXP_VERSION');
            return false;
        }

        extract(unpack('Nversion', $this->_string_shift($response, 4)));
        $this->version = $version;
        while (!empty($response)) {
            extract(unpack('Nlength', $this->_string_shift($response, 4)));
            $key = $this->_string_shift($response, $length);
            extract(unpack('Nlength', $this->_string_shift($response, 4)));
            $value = $this->_string_shift($response, $length);
            $this->extensions[$key] = $value;
        }

        /*
         SFTPv4+ defines a 'newline' extension.  SFTPv3 seems to have unofficial support for it via 'newline@vandyke.com',
         however, I'm not sure what 'newline@vandyke.com' is supposed to do (the fact that it's unofficial means that it's
         not in the official SFTPv3 specs) and 'newline@vandyke.com' / 'newline' are likely not drop-in substitutes for
         one another due to the fact that 'newline' comes with a SSH_FXF_TEXT bitmask whereas it seems unlikely that
         'newline@vandyke.com' would.
        */
        /*
        if (isset($this->extensions['newline@vandyke.com'])) {
            $this->extensions['newline'] = $this->extensions['newline@vandyke.com'];
            unset($this->extensions['newline@vandyke.com']);
        }
        */

        $this->request_id = 1;

        /*
         A Note on SFTPv4/5/6 support:
         <http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-5.1> states the following:

         "If the client wishes to interoperate with servers that support noncontiguous version
          numbers it SHOULD send '3'"

         Given that the server only sends its version number after the client has already done so, the above
         seems to be suggesting that v3 should be the default version.  This makes sense given that v3 is the
         most popular.

         <http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-5.5> states the following;

         "If the server did not send the "versions" extension, or the version-from-list was not included, the
          server MAY send a status response describing the failure, but MUST then close the channel without
          processing any further requests."

         So what do you do if you have a client whose initial SSH_FXP_INIT packet says it implements v3 and
         a server whose initial SSH_FXP_VERSION reply says it implements v4 and only v4?  If it only implements
         v4, the "versions" extension is likely not going to have been sent so version re-negotiation as discussed
         in draft-ietf-secsh-filexfer-13 would be quite impossible.  As such, what \phpseclib\Net\SFTP would do is close the
         channel and reopen it with a new and updated SSH_FXP_INIT packet.
        */
        switch ($this->version) {
            case 2:
            case 3:
                break;
            default:
                return false;
        }

        $this->pwd = $this->_realpath('.');

        $this->_update_stat_cache($this->pwd, array());

        return true;
    }

    function disableStatCache()
    {
        $this->use_stat_cache = false;
    }

    function enableStatCache()
    {
        $this->use_stat_cache = true;
    }

    function clearStatCache()
    {
        $this->stat_cache = array();
    }

    function pwd()
    {
        return $this->pwd;
    }

    function _logError($response, $status = -1)
    {
        if ($status == -1) {
            extract(unpack('Nstatus', $this->_string_shift($response, 4)));
        }

        $error = $this->status_codes[$status];

        if ($this->version > 2) {
            extract(unpack('Nlength', $this->_string_shift($response, 4)));
            $this->sftp_errors[] = $error . ': ' . $this->_string_shift($response, $length);
        } else {
            $this->sftp_errors[] = $error;
        }
    }

    function _realpath($path)
    {
        if ($this->pwd === false) {
            // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.9
            if (!$this->_send_sftp_packet(NET_SFTP_REALPATH, pack('Na*', strlen($path), $path))) {
                return false;
            }

            $response = $this->_get_sftp_packet();
            switch ($this->packet_type) {
                case NET_SFTP_NAME:
                    // although SSH_FXP_NAME is implemented differently in SFTPv3 than it is in SFTPv4+, the following
                    // should work on all SFTP versions since the only part of the SSH_FXP_NAME packet the following looks
                    // at is the first part and that part is defined the same in SFTP versions 3 through 6.
                    $this->_string_shift($response, 4); // skip over the count - it should be 1, anyway
                    extract(unpack('Nlength', $this->_string_shift($response, 4)));
                    return $this->_string_shift($response, $length);
                case NET_SFTP_STATUS:
                    $this->_logError($response);
                    return false;
                default:
                    user_error('Expected SSH_FXP_NAME or SSH_FXP_STATUS');
                    return false;
            }
        }

        if ($path[0] != '/') {
            $path = $this->pwd . '/' . $path;
        }

        $path = explode('/', $path);
        $new = array();
        foreach ($path as $dir) {
            if (!strlen($dir)) {
                continue;
            }
            switch ($dir) {
                case '..':
                    array_pop($new);
                case '.':
                    break;
                default:
                    $new[] = $dir;
            }
        }

        return '/' . implode('/', $new);
    }

    function chdir($dir)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        // assume current dir if $dir is empty
        if ($dir === '') {
            $dir = './';
        // suffix a slash if needed
        } elseif ($dir[strlen($dir) - 1] != '/') {
            $dir.= '/';
        }

        $dir = $this->_realpath($dir);

        // confirm that $dir is, in fact, a valid directory
        if ($this->use_stat_cache && is_array($this->_query_stat_cache($dir))) {
            $this->pwd = $dir;
            return true;
        }

        // we could do a stat on the alleged $dir to see if it's a directory but that doesn't tell us
        // the currently logged in user has the appropriate permissions or not. maybe you could see if
        // the file's uid / gid match the currently logged in user's uid / gid but how there's no easy
        // way to get those with SFTP

        if (!$this->_send_sftp_packet(NET_SFTP_OPENDIR, pack('Na*', strlen($dir), $dir))) {
            return false;
        }

        // see \phpseclib\Net\SFTP::nlist() for a more thorough explanation of the following
        $response = $this->_get_sftp_packet();
        switch ($this->packet_type) {
            case NET_SFTP_HANDLE:
                $handle = substr($response, 4);
                break;
            case NET_SFTP_STATUS:
                $this->_logError($response);
                return false;
            default:
                user_error('Expected SSH_FXP_HANDLE or SSH_FXP_STATUS');
                return false;
        }

        if (!$this->_close_handle($handle)) {
            return false;
        }

        $this->_update_stat_cache($dir, array());

        $this->pwd = $dir;
        return true;
    }

    function nlist($dir = '.', $recursive = false)
    {
        return $this->_nlist_helper($dir, $recursive, '');
    }

    function _nlist_helper($dir, $recursive, $relativeDir)
    {
        $files = $this->_list($dir, false);

        if (!$recursive) {
            return $files;
        }

        $result = array();
        foreach ($files as $value) {
            if ($value == '.' || $value == '..') {
                if ($relativeDir == '') {
                    $result[] = $value;
                }
                continue;
            }
            if (is_array($this->_query_stat_cache($this->_realpath($dir . '/' . $value)))) {
                $temp = $this->_nlist_helper($dir . '/' . $value, true, $relativeDir . $value . '/');
                $result = array_merge($result, $temp);
            } else {
                $result[] = $relativeDir . $value;
            }
        }

        return $result;
    }

    function rawlist($dir = '.', $recursive = false)
    {
        $files = $this->_list($dir, true);
        if (!$recursive || $files === false) {
            return $files;
        }

        static $depth = 0;

        foreach ($files as $key => $value) {
            if ($depth != 0 && $key == '..') {
                unset($files[$key]);
                continue;
            }
            if ($key != '.' && $key != '..' && is_array($this->_query_stat_cache($this->_realpath($dir . '/' . $key)))) {
                $depth++;
                $files[$key] = $this->rawlist($dir . '/' . $key, true);
                $depth--;
            } else {
                $files[$key] = (object) $value;
            }
        }

        return $files;
    }

    function _list($dir, $raw = true)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $dir = $this->_realpath($dir . '/');
        if ($dir === false) {
            return false;
        }

        // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.1.2
        if (!$this->_send_sftp_packet(NET_SFTP_OPENDIR, pack('Na*', strlen($dir), $dir))) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        switch ($this->packet_type) {
            case NET_SFTP_HANDLE:
                // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-9.2
                // since 'handle' is the last field in the SSH_FXP_HANDLE packet, we'll just remove the first four bytes that
                // represent the length of the string and leave it at that
                $handle = substr($response, 4);
                break;
            case NET_SFTP_STATUS:
                // presumably SSH_FX_NO_SUCH_FILE or SSH_FX_PERMISSION_DENIED
                $this->_logError($response);
                return false;
            default:
                user_error('Expected SSH_FXP_HANDLE or SSH_FXP_STATUS');
                return false;
        }

        $this->_update_stat_cache($dir, array());

        $contents = array();
        while (true) {
            // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.2.2
            // why multiple SSH_FXP_READDIR packets would be sent when the response to a single one can span arbitrarily many
            // SSH_MSG_CHANNEL_DATA messages is not known to me.
            if (!$this->_send_sftp_packet(NET_SFTP_READDIR, pack('Na*', strlen($handle), $handle))) {
                return false;
            }

            $response = $this->_get_sftp_packet();
            switch ($this->packet_type) {
                case NET_SFTP_NAME:
                    extract(unpack('Ncount', $this->_string_shift($response, 4)));
                    for ($i = 0; $i < $count; $i++) {
                        extract(unpack('Nlength', $this->_string_shift($response, 4)));
                        $shortname = $this->_string_shift($response, $length);
                        extract(unpack('Nlength', $this->_string_shift($response, 4)));
                        $longname = $this->_string_shift($response, $length);
                        $attributes = $this->_parseAttributes($response);
                        if (!isset($attributes['type'])) {
                            $fileType = $this->_parseLongname($longname);
                            if ($fileType) {
                                $attributes['type'] = $fileType;
                            }
                        }
                        $contents[$shortname] = $attributes + array('filename' => $shortname);

                        if (isset($attributes['type']) && $attributes['type'] == NET_SFTP_TYPE_DIRECTORY && ($shortname != '.' && $shortname != '..')) {
                            $this->_update_stat_cache($dir . '/' . $shortname, array());
                        } else {
                            if ($shortname == '..') {
                                $temp = $this->_realpath($dir . '/..') . '/.';
                            } else {
                                $temp = $dir . '/' . $shortname;
                            }
                            $this->_update_stat_cache($temp, (object) array('lstat' => $attributes));
                        }
                        // SFTPv6 has an optional boolean end-of-list field, but we'll ignore that, since the
                        // final SSH_FXP_STATUS packet should tell us that, already.
                    }
                    break;
                case NET_SFTP_STATUS:
                    extract(unpack('Nstatus', $this->_string_shift($response, 4)));
                    if ($status != NET_SFTP_STATUS_EOF) {
                        $this->_logError($response, $status);
                        return false;
                    }
                    break 2;
                default:
                    user_error('Expected SSH_FXP_NAME or SSH_FXP_STATUS');
                    return false;
            }
        }

        if (!$this->_close_handle($handle)) {
            return false;
        }

        if (count($this->sortOptions)) {
            uasort($contents, array(&$this, '_comparator'));
        }

        return $raw ? $contents : array_keys($contents);
    }

    function _comparator($a, $b)
    {
        switch (true) {
            case $a['filename'] === '.' || $b['filename'] === '.':
                if ($a['filename'] === $b['filename']) {
                    return 0;
                }
                return $a['filename'] === '.' ? -1 : 1;
            case $a['filename'] === '..' || $b['filename'] === '..':
                if ($a['filename'] === $b['filename']) {
                    return 0;
                }
                return $a['filename'] === '..' ? -1 : 1;
            case isset($a['type']) && $a['type'] === NET_SFTP_TYPE_DIRECTORY:
                if (!isset($b['type'])) {
                    return 1;
                }
                if ($b['type'] !== $a['type']) {
                    return -1;
                }
                break;
            case isset($b['type']) && $b['type'] === NET_SFTP_TYPE_DIRECTORY:
                return 1;
        }
        foreach ($this->sortOptions as $sort => $order) {
            if (!isset($a[$sort]) || !isset($b[$sort])) {
                if (isset($a[$sort])) {
                    return -1;
                }
                if (isset($b[$sort])) {
                    return 1;
                }
                return 0;
            }
            switch ($sort) {
                case 'filename':
                    $result = strcasecmp($a['filename'], $b['filename']);
                    if ($result) {
                        return $order === SORT_DESC ? -$result : $result;
                    }
                    break;
                case 'permissions':
                case 'mode':
                    $a[$sort]&= 07777;
                    $b[$sort]&= 07777;
                default:
                    if ($a[$sort] === $b[$sort]) {
                        break;
                    }
                    return $order === SORT_ASC ? $a[$sort] - $b[$sort] : $b[$sort] - $a[$sort];
            }
        }
    }

    function setListOrder()
    {
        $this->sortOptions = array();
        $args = func_get_args();
        if (empty($args)) {
            return;
        }
        $len = count($args) & 0x7FFFFFFE;
        for ($i = 0; $i < $len; $i+=2) {
            $this->sortOptions[$args[$i]] = $args[$i + 1];
        }
        if (!count($this->sortOptions)) {
            $this->sortOptions = array('bogus' => true);
        }
    }

    function size($filename)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $result = $this->stat($filename);
        if ($result === false) {
            return false;
        }
        return isset($result['size']) ? $result['size'] : -1;
    }

    function _update_stat_cache($path, $value)
    {
        if ($this->use_stat_cache === false) {
            return;
        }

        // preg_replace('#^/|/(?=/)|/$#', '', $dir) == str_replace('//', '/', trim($path, '/'))
        $dirs = explode('/', preg_replace('#^/|/(?=/)|/$#', '', $path));

        $temp = &$this->stat_cache;
        $max = count($dirs) - 1;
        foreach ($dirs as $i => $dir) {
            // if $temp is an object that means one of two things.
            //  1. a file was deleted and changed to a directory behind phpseclib's back
            //  2. it's a symlink. when lstat is done it's unclear what it's a symlink to
            if (is_object($temp)) {
                $temp = array();
            }
            if (!isset($temp[$dir])) {
                $temp[$dir] = array();
            }
            if ($i === $max) {
                if (is_object($temp[$dir])) {
                    if (!isset($value->stat) && isset($temp[$dir]->stat)) {
                        $value->stat = $temp[$dir]->stat;
                    }
                    if (!isset($value->lstat) && isset($temp[$dir]->lstat)) {
                        $value->lstat = $temp[$dir]->lstat;
                    }
                }
                $temp[$dir] = $value;
                break;
            }
            $temp = &$temp[$dir];
        }
    }

    function _remove_from_stat_cache($path)
    {
        $dirs = explode('/', preg_replace('#^/|/(?=/)|/$#', '', $path));

        $temp = &$this->stat_cache;
        $max = count($dirs) - 1;
        foreach ($dirs as $i => $dir) {
            if ($i === $max) {
                unset($temp[$dir]);
                return true;
            }
            if (!isset($temp[$dir])) {
                return false;
            }
            $temp = &$temp[$dir];
        }
    }

    function _query_stat_cache($path)
    {
        $dirs = explode('/', preg_replace('#^/|/(?=/)|/$#', '', $path));

        $temp = &$this->stat_cache;
        foreach ($dirs as $dir) {
            if (!isset($temp[$dir])) {
                return null;
            }
            $temp = &$temp[$dir];
        }
        return $temp;
    }

    function stat($filename)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $filename = $this->_realpath($filename);
        if ($filename === false) {
            return false;
        }

        if ($this->use_stat_cache) {
            $result = $this->_query_stat_cache($filename);
            if (is_array($result) && isset($result['.']) && isset($result['.']->stat)) {
                return $result['.']->stat;
            }
            if (is_object($result) && isset($result->stat)) {
                return $result->stat;
            }
        }

        $stat = $this->_stat($filename, NET_SFTP_STAT);
        if ($stat === false) {
            $this->_remove_from_stat_cache($filename);
            return false;
        }
        if (isset($stat['type'])) {
            if ($stat['type'] == NET_SFTP_TYPE_DIRECTORY) {
                $filename.= '/.';
            }
            $this->_update_stat_cache($filename, (object) array('stat' => $stat));
            return $stat;
        }

        $pwd = $this->pwd;
        $stat['type'] = $this->chdir($filename) ?
            NET_SFTP_TYPE_DIRECTORY :
            NET_SFTP_TYPE_REGULAR;
        $this->pwd = $pwd;

        if ($stat['type'] == NET_SFTP_TYPE_DIRECTORY) {
            $filename.= '/.';
        }
        $this->_update_stat_cache($filename, (object) array('stat' => $stat));

        return $stat;
    }

    function lstat($filename)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $filename = $this->_realpath($filename);
        if ($filename === false) {
            return false;
        }

        if ($this->use_stat_cache) {
            $result = $this->_query_stat_cache($filename);
            if (is_array($result) && isset($result['.']) && isset($result['.']->lstat)) {
                return $result['.']->lstat;
            }
            if (is_object($result) && isset($result->lstat)) {
                return $result->lstat;
            }
        }

        $lstat = $this->_stat($filename, NET_SFTP_LSTAT);
        if ($lstat === false) {
            $this->_remove_from_stat_cache($filename);
            return false;
        }
        if (isset($lstat['type'])) {
            if ($lstat['type'] == NET_SFTP_TYPE_DIRECTORY) {
                $filename.= '/.';
            }
            $this->_update_stat_cache($filename, (object) array('lstat' => $lstat));
            return $lstat;
        }

        $stat = $this->_stat($filename, NET_SFTP_STAT);

        if ($lstat != $stat) {
            $lstat = array_merge($lstat, array('type' => NET_SFTP_TYPE_SYMLINK));
            $this->_update_stat_cache($filename, (object) array('lstat' => $lstat));
            return $stat;
        }

        $pwd = $this->pwd;
        $lstat['type'] = $this->chdir($filename) ?
            NET_SFTP_TYPE_DIRECTORY :
            NET_SFTP_TYPE_REGULAR;
        $this->pwd = $pwd;

        if ($lstat['type'] == NET_SFTP_TYPE_DIRECTORY) {
            $filename.= '/.';
        }
        $this->_update_stat_cache($filename, (object) array('lstat' => $lstat));

        return $lstat;
    }

    function _stat($filename, $type)
    {
        // SFTPv4+ adds an additional 32-bit integer field - flags - to the following:
        $packet = pack('Na*', strlen($filename), $filename);
        if (!$this->_send_sftp_packet($type, $packet)) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        switch ($this->packet_type) {
            case NET_SFTP_ATTRS:
                return $this->_parseAttributes($response);
            case NET_SFTP_STATUS:
                $this->_logError($response);
                return false;
        }

        user_error('Expected SSH_FXP_ATTRS or SSH_FXP_STATUS');
        return false;
    }

    function truncate($filename, $new_size)
    {
        $attr = pack('N3', NET_SFTP_ATTR_SIZE, $new_size / 4294967296, $new_size); // 4294967296 == 0x100000000 == 1<<32

        return $this->_setstat($filename, $attr, false);
    }

    function touch($filename, $time = null, $atime = null)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $filename = $this->_realpath($filename);
        if ($filename === false) {
            return false;
        }

        if (!isset($time)) {
            $time = time();
        }
        if (!isset($atime)) {
            $atime = $time;
        }

        $flags = NET_SFTP_OPEN_WRITE | NET_SFTP_OPEN_CREATE | NET_SFTP_OPEN_EXCL;
        $attr = pack('N3', NET_SFTP_ATTR_ACCESSTIME, $time, $atime);
        $packet = pack('Na*Na*', strlen($filename), $filename, $flags, $attr);
        if (!$this->_send_sftp_packet(NET_SFTP_OPEN, $packet)) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        switch ($this->packet_type) {
            case NET_SFTP_HANDLE:
                return $this->_close_handle(substr($response, 4));
            case NET_SFTP_STATUS:
                $this->_logError($response);
                break;
            default:
                user_error('Expected SSH_FXP_HANDLE or SSH_FXP_STATUS');
                return false;
        }

        return $this->_setstat($filename, $attr, false);
    }

    function chown($filename, $uid, $recursive = false)
    {
        // quoting from <http://www.kernel.org/doc/man-pages/online/pages/man2/chown.2.html>,
        // "if the owner or group is specified as -1, then that ID is not changed"
        $attr = pack('N3', NET_SFTP_ATTR_UIDGID, $uid, -1);

        return $this->_setstat($filename, $attr, $recursive);
    }

    function chgrp($filename, $gid, $recursive = false)
    {
        $attr = pack('N3', NET_SFTP_ATTR_UIDGID, -1, $gid);

        return $this->_setstat($filename, $attr, $recursive);
    }

    function chmod($mode, $filename, $recursive = false)
    {
        if (is_string($mode) && is_int($filename)) {
            $temp = $mode;
            $mode = $filename;
            $filename = $temp;
        }

        $attr = pack('N2', NET_SFTP_ATTR_PERMISSIONS, $mode & 07777);
        if (!$this->_setstat($filename, $attr, $recursive)) {
            return false;
        }
        if ($recursive) {
            return true;
        }

        $filename = $this->_realPath($filename);
        // rather than return what the permissions *should* be, we'll return what they actually are.  this will also
        // tell us if the file actually exists.
        // incidentally, SFTPv4+ adds an additional 32-bit integer field - flags - to the following:
        $packet = pack('Na*', strlen($filename), $filename);
        if (!$this->_send_sftp_packet(NET_SFTP_STAT, $packet)) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        switch ($this->packet_type) {
            case NET_SFTP_ATTRS:
                $attrs = $this->_parseAttributes($response);
                return $attrs['permissions'];
            case NET_SFTP_STATUS:
                $this->_logError($response);
                return false;
        }

        user_error('Expected SSH_FXP_ATTRS or SSH_FXP_STATUS');
        return false;
    }

    function _setstat($filename, $attr, $recursive)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $filename = $this->_realpath($filename);
        if ($filename === false) {
            return false;
        }

        $this->_remove_from_stat_cache($filename);

        if ($recursive) {
            $i = 0;
            $result = $this->_setstat_recursive($filename, $attr, $i);
            $this->_read_put_responses($i);
            return $result;
        }

        // SFTPv4+ has an additional byte field - type - that would need to be sent, as well. setting it to
        // SSH_FILEXFER_TYPE_UNKNOWN might work. if not, we'd have to do an SSH_FXP_STAT before doing an SSH_FXP_SETSTAT.
        if (!$this->_send_sftp_packet(NET_SFTP_SETSTAT, pack('Na*a*', strlen($filename), $filename, $attr))) {
            return false;
        }

        /*
         "Because some systems must use separate system calls to set various attributes, it is possible that a failure
          response will be returned, but yet some of the attributes may be have been successfully modified.  If possible,
          servers SHOULD avoid this situation; however, clients MUST be aware that this is possible."

          -- http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.6
        */
        $response = $this->_get_sftp_packet();
        if ($this->packet_type != NET_SFTP_STATUS) {
            user_error('Expected SSH_FXP_STATUS');
            return false;
        }

        extract(unpack('Nstatus', $this->_string_shift($response, 4)));
        if ($status != NET_SFTP_STATUS_OK) {
            $this->_logError($response, $status);
            return false;
        }

        return true;
    }

    function _setstat_recursive($path, $attr, &$i)
    {
        if (!$this->_read_put_responses($i)) {
            return false;
        }
        $i = 0;
        $entries = $this->_list($path, true);

        if ($entries === false) {
            return $this->_setstat($path, $attr, false);
        }

        // normally $entries would have at least . and .. but it might not if the directories
        // permissions didn't allow reading
        if (empty($entries)) {
            return false;
        }

        unset($entries['.'], $entries['..']);
        foreach ($entries as $filename => $props) {
            if (!isset($props['type'])) {
                return false;
            }

            $temp = $path . '/' . $filename;
            if ($props['type'] == NET_SFTP_TYPE_DIRECTORY) {
                if (!$this->_setstat_recursive($temp, $attr, $i)) {
                    return false;
                }
            } else {
                if (!$this->_send_sftp_packet(NET_SFTP_SETSTAT, pack('Na*a*', strlen($temp), $temp, $attr))) {
                    return false;
                }

                $i++;

                if ($i >= NET_SFTP_QUEUE_SIZE) {
                    if (!$this->_read_put_responses($i)) {
                        return false;
                    }
                    $i = 0;
                }
            }
        }

        if (!$this->_send_sftp_packet(NET_SFTP_SETSTAT, pack('Na*a*', strlen($path), $path, $attr))) {
            return false;
        }

        $i++;

        if ($i >= NET_SFTP_QUEUE_SIZE) {
            if (!$this->_read_put_responses($i)) {
                return false;
            }
            $i = 0;
        }

        return true;
    }

    function readlink($link)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $link = $this->_realpath($link);

        if (!$this->_send_sftp_packet(NET_SFTP_READLINK, pack('Na*', strlen($link), $link))) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        switch ($this->packet_type) {
            case NET_SFTP_NAME:
                break;
            case NET_SFTP_STATUS:
                $this->_logError($response);
                return false;
            default:
                user_error('Expected SSH_FXP_NAME or SSH_FXP_STATUS');
                return false;
        }

        extract(unpack('Ncount', $this->_string_shift($response, 4)));
        // the file isn't a symlink
        if (!$count) {
            return false;
        }

        extract(unpack('Nlength', $this->_string_shift($response, 4)));
        return $this->_string_shift($response, $length);
    }

    function symlink($target, $link)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $target = $this->_realpath($target);
        $link = $this->_realpath($link);

        $packet = pack('Na*Na*', strlen($target), $target, strlen($link), $link);
        if (!$this->_send_sftp_packet(NET_SFTP_SYMLINK, $packet)) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        if ($this->packet_type != NET_SFTP_STATUS) {
            user_error('Expected SSH_FXP_STATUS');
            return false;
        }

        extract(unpack('Nstatus', $this->_string_shift($response, 4)));
        if ($status != NET_SFTP_STATUS_OK) {
            $this->_logError($response, $status);
            return false;
        }

        return true;
    }

    function mkdir($dir, $mode = -1, $recursive = false)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $dir = $this->_realpath($dir);
        // by not providing any permissions, hopefully the server will use the logged in users umask - their
        // default permissions.
        $attr = $mode == -1 ? "\0\0\0\0" : pack('N2', NET_SFTP_ATTR_PERMISSIONS, $mode & 07777);

        if ($recursive) {
            $dirs = explode('/', preg_replace('#/(?=/)|/$#', '', $dir));
            if (empty($dirs[0])) {
                array_shift($dirs);
                $dirs[0] = '/' . $dirs[0];
            }
            for ($i = 0; $i < count($dirs); $i++) {
                $temp = array_slice($dirs, 0, $i + 1);
                $temp = implode('/', $temp);
                $result = $this->_mkdir_helper($temp, $attr);
            }
            return $result;
        }

        return $this->_mkdir_helper($dir, $attr);
    }

    function _mkdir_helper($dir, $attr)
    {
        if (!$this->_send_sftp_packet(NET_SFTP_MKDIR, pack('Na*a*', strlen($dir), $dir, $attr))) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        if ($this->packet_type != NET_SFTP_STATUS) {
            user_error('Expected SSH_FXP_STATUS');
            return false;
        }

        extract(unpack('Nstatus', $this->_string_shift($response, 4)));
        if ($status != NET_SFTP_STATUS_OK) {
            $this->_logError($response, $status);
            return false;
        }

        return true;
    }

    function rmdir($dir)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $dir = $this->_realpath($dir);
        if ($dir === false) {
            return false;
        }

        if (!$this->_send_sftp_packet(NET_SFTP_RMDIR, pack('Na*', strlen($dir), $dir))) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        if ($this->packet_type != NET_SFTP_STATUS) {
            user_error('Expected SSH_FXP_STATUS');
            return false;
        }

        extract(unpack('Nstatus', $this->_string_shift($response, 4)));
        if ($status != NET_SFTP_STATUS_OK) {
            // presumably SSH_FX_NO_SUCH_FILE or SSH_FX_PERMISSION_DENIED?
            $this->_logError($response, $status);
            return false;
        }

        $this->_remove_from_stat_cache($dir);
        // the following will do a soft delete, which would be useful if you deleted a file
        // and then tried to do a stat on the deleted file. the above, in contrast, does
        // a hard delete
        //$this->_update_stat_cache($dir, false);

        return true;
    }

    function put($remote_file, $data, $mode = self::SOURCE_STRING, $start = -1, $local_start = -1, $progressCallback = null)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $remote_file = $this->_realpath($remote_file);
        if ($remote_file === false) {
            return false;
        }

        $this->_remove_from_stat_cache($remote_file);

        $flags = NET_SFTP_OPEN_WRITE | NET_SFTP_OPEN_CREATE;
        // according to the SFTP specs, NET_SFTP_OPEN_APPEND should "force all writes to append data at the end of the file."
        // in practice, it doesn't seem to do that.
        //$flags|= ($mode & self::RESUME) ? NET_SFTP_OPEN_APPEND : NET_SFTP_OPEN_TRUNCATE;

        if ($start >= 0) {
            $offset = $start;
        } elseif ($mode & self::RESUME) {
            // if NET_SFTP_OPEN_APPEND worked as it should _size() wouldn't need to be called
            $size = $this->size($remote_file);
            $offset = $size !== false ? $size : 0;
        } else {
            $offset = 0;
            $flags|= NET_SFTP_OPEN_TRUNCATE;
        }

        $packet = pack('Na*N2', strlen($remote_file), $remote_file, $flags, 0);
        if (!$this->_send_sftp_packet(NET_SFTP_OPEN, $packet)) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        switch ($this->packet_type) {
            case NET_SFTP_HANDLE:
                $handle = substr($response, 4);
                break;
            case NET_SFTP_STATUS:
                $this->_logError($response);
                return false;
            default:
                user_error('Expected SSH_FXP_HANDLE or SSH_FXP_STATUS');
                return false;
        }

        // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.2.3
        $dataCallback = false;
        switch (true) {
            case $mode & self::SOURCE_CALLBACK:
                if (!is_callable($data)) {
                    user_error("\$data should be is_callable() if you specify SOURCE_CALLBACK flag");
                }
                $dataCallback = $data;
                // do nothing
                break;
            case is_resource($data):
                $mode = $mode & ~self::SOURCE_LOCAL_FILE;
                $fp = $data;
                break;
            case $mode & self::SOURCE_LOCAL_FILE:
                if (!is_file($data)) {
                    user_error("$data is not a valid file");
                    return false;
                }
                $fp = @fopen($data, 'rb');
                if (!$fp) {
                    return false;
                }
        }

        if (isset($fp)) {
            $stat = fstat($fp);
            $size = $stat['size'];

            if ($local_start >= 0) {
                fseek($fp, $local_start);
                $size-= $local_start;
            }
        } elseif ($dataCallback) {
            $size = 0;
        } else {
            $size = strlen($data);
        }

        $sent = 0;
        $size = $size < 0 ? ($size & 0x7FFFFFFF) + 0x80000000 : $size;

        $sftp_packet_size = 4096; // PuTTY uses 4096
        // make the SFTP packet be exactly 4096 bytes by including the bytes in the NET_SFTP_WRITE packets "header"
        $sftp_packet_size-= strlen($handle) + 25;
        $i = 0;
        while ($dataCallback || $sent < $size) {
            if ($dataCallback) {
                $temp = call_user_func($dataCallback, $sftp_packet_size);
                if (is_null($temp)) {
                    break;
                }
            } else {
                $temp = isset($fp) ? fread($fp, $sftp_packet_size) : substr($data, $sent, $sftp_packet_size);
            }
            $subtemp = $offset + $sent;
            $packet = pack('Na*N3a*', strlen($handle), $handle, $subtemp / 4294967296, $subtemp, strlen($temp), $temp);
            if (!$this->_send_sftp_packet(NET_SFTP_WRITE, $packet)) {
                if ($mode & self::SOURCE_LOCAL_FILE) {
                    fclose($fp);
                }
                return false;
            }
            $sent+= strlen($temp);
            if (is_callable($progressCallback)) {
                call_user_func($progressCallback, $sent);
            }

            $i++;

            if ($i == NET_SFTP_QUEUE_SIZE) {
                if (!$this->_read_put_responses($i)) {
                    $i = 0;
                    break;
                }
                $i = 0;
            }
        }

        if (!$this->_read_put_responses($i)) {
            if ($mode & self::SOURCE_LOCAL_FILE) {
                fclose($fp);
            }
            $this->_close_handle($handle);
            return false;
        }

        if ($mode & self::SOURCE_LOCAL_FILE) {
            fclose($fp);
        }

        return $this->_close_handle($handle);
    }

    function _read_put_responses($i)
    {
        while ($i--) {
            $response = $this->_get_sftp_packet();
            if ($this->packet_type != NET_SFTP_STATUS) {
                user_error('Expected SSH_FXP_STATUS');
                return false;
            }

            extract(unpack('Nstatus', $this->_string_shift($response, 4)));
            if ($status != NET_SFTP_STATUS_OK) {
                $this->_logError($response, $status);
                break;
            }
        }

        return $i < 0;
    }

    function _close_handle($handle)
    {
        if (!$this->_send_sftp_packet(NET_SFTP_CLOSE, pack('Na*', strlen($handle), $handle))) {
            return false;
        }

        // "The client MUST release all resources associated with the handle regardless of the status."
        //  -- http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.1.3
        $response = $this->_get_sftp_packet();
        if ($this->packet_type != NET_SFTP_STATUS) {
            user_error('Expected SSH_FXP_STATUS');
            return false;
        }

        extract(unpack('Nstatus', $this->_string_shift($response, 4)));
        if ($status != NET_SFTP_STATUS_OK) {
            $this->_logError($response, $status);
            return false;
        }

        return true;
    }

    function get($remote_file, $local_file = false, $offset = 0, $length = -1)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $remote_file = $this->_realpath($remote_file);
        if ($remote_file === false) {
            return false;
        }

        $packet = pack('Na*N2', strlen($remote_file), $remote_file, NET_SFTP_OPEN_READ, 0);
        if (!$this->_send_sftp_packet(NET_SFTP_OPEN, $packet)) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        switch ($this->packet_type) {
            case NET_SFTP_HANDLE:
                $handle = substr($response, 4);
                break;
            case NET_SFTP_STATUS: // presumably SSH_FX_NO_SUCH_FILE or SSH_FX_PERMISSION_DENIED
                $this->_logError($response);
                return false;
            default:
                user_error('Expected SSH_FXP_HANDLE or SSH_FXP_STATUS');
                return false;
        }

        if (is_resource($local_file)) {
            $fp = $local_file;
            $stat = fstat($fp);
            $res_offset = $stat['size'];
        } else {
            $res_offset = 0;
            if ($local_file !== false) {
                $fp = fopen($local_file, 'wb');
                if (!$fp) {
                    return false;
                }
            } else {
                $content = '';
            }
        }

        $fclose_check = $local_file !== false && !is_resource($local_file);

        $start = $offset;
        $size = $this->max_sftp_packet < $length || $length < 0 ? $this->max_sftp_packet : $length;
        while (true) {
            $packet = pack('Na*N3', strlen($handle), $handle, $offset / 4294967296, $offset, $size);
            if (!$this->_send_sftp_packet(NET_SFTP_READ, $packet)) {
                if ($fclose_check) {
                    fclose($fp);
                }
                return false;
            }

            $response = $this->_get_sftp_packet();
            switch ($this->packet_type) {
                case NET_SFTP_DATA:
                    $temp = substr($response, 4);
                    $offset+= strlen($temp);
                    if ($local_file === false) {
                        $content.= $temp;
                    } else {
                        fputs($fp, $temp);
                    }
                    break;
                case NET_SFTP_STATUS:
                    // could, in theory, return false if !strlen($content) but we'll hold off for the time being
                    $this->_logError($response);
                    break 2;
                default:
                    user_error('Expected SSH_FXP_DATA or SSH_FXP_STATUS');
                    if ($fclose_check) {
                        fclose($fp);
                    }
                    return false;
            }

            if ($length > 0 && $length <= $offset - $start) {
                break;
            }
        }

        if ($length > 0 && $length <= $offset - $start) {
            if ($local_file === false) {
                $content = substr($content, 0, $length);
            } else {
                ftruncate($fp, $length + $res_offset);
            }
        }

        if ($fclose_check) {
            fclose($fp);
        }

        if (!$this->_close_handle($handle)) {
            return false;
        }

        // if $content isn't set that means a file was written to
        return isset($content) ? $content : true;
    }

    function delete($path, $recursive = true)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $path = $this->_realpath($path);
        if ($path === false) {
            return false;
        }

        // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.3
        if (!$this->_send_sftp_packet(NET_SFTP_REMOVE, pack('Na*', strlen($path), $path))) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        if ($this->packet_type != NET_SFTP_STATUS) {
            user_error('Expected SSH_FXP_STATUS');
            return false;
        }

        // if $status isn't SSH_FX_OK it's probably SSH_FX_NO_SUCH_FILE or SSH_FX_PERMISSION_DENIED
        extract(unpack('Nstatus', $this->_string_shift($response, 4)));
        if ($status != NET_SFTP_STATUS_OK) {
            $this->_logError($response, $status);
            if (!$recursive) {
                return false;
            }
            $i = 0;
            $result = $this->_delete_recursive($path, $i);
            $this->_read_put_responses($i);
            return $result;
        }

        $this->_remove_from_stat_cache($path);

        return true;
    }

    function _delete_recursive($path, &$i)
    {
        if (!$this->_read_put_responses($i)) {
            return false;
        }
        $i = 0;
        $entries = $this->_list($path, true);

        // normally $entries would have at least . and .. but it might not if the directories
        // permissions didn't allow reading
        if (empty($entries)) {
            return false;
        }

        unset($entries['.'], $entries['..']);
        foreach ($entries as $filename => $props) {
            if (!isset($props['type'])) {
                return false;
            }

            $temp = $path . '/' . $filename;
            if ($props['type'] == NET_SFTP_TYPE_DIRECTORY) {
                if (!$this->_delete_recursive($temp, $i)) {
                    return false;
                }
            } else {
                if (!$this->_send_sftp_packet(NET_SFTP_REMOVE, pack('Na*', strlen($temp), $temp))) {
                    return false;
                }
                $this->_remove_from_stat_cache($temp);

                $i++;

                if ($i >= NET_SFTP_QUEUE_SIZE) {
                    if (!$this->_read_put_responses($i)) {
                        return false;
                    }
                    $i = 0;
                }
            }
        }

        if (!$this->_send_sftp_packet(NET_SFTP_RMDIR, pack('Na*', strlen($path), $path))) {
            return false;
        }
        $this->_remove_from_stat_cache($path);

        $i++;

        if ($i >= NET_SFTP_QUEUE_SIZE) {
            if (!$this->_read_put_responses($i)) {
                return false;
            }
            $i = 0;
        }

        return true;
    }

    function file_exists($path)
    {
        if ($this->use_stat_cache) {
            $path = $this->_realpath($path);

            $result = $this->_query_stat_cache($path);

            if (isset($result)) {
                // return true if $result is an array or if it's an stdClass object
                return $result !== false;
            }
        }

        return $this->stat($path) !== false;
    }

    function is_dir($path)
    {
        $result = $this->_get_stat_cache_prop($path, 'type');
        if ($result === false) {
            return false;
        }
        return $result === NET_SFTP_TYPE_DIRECTORY;
    }

    function is_file($path)
    {
        $result = $this->_get_stat_cache_prop($path, 'type');
        if ($result === false) {
            return false;
        }
        return $result === NET_SFTP_TYPE_REGULAR;
    }

    function is_link($path)
    {
        $result = $this->_get_lstat_cache_prop($path, 'type');
        if ($result === false) {
            return false;
        }
        return $result === NET_SFTP_TYPE_SYMLINK;
    }

    function fileatime($path)
    {
        return $this->_get_stat_cache_prop($path, 'atime');
    }

    function filemtime($path)
    {
        return $this->_get_stat_cache_prop($path, 'mtime');
    }

    function fileperms($path)
    {
        return $this->_get_stat_cache_prop($path, 'permissions');
    }

    function fileowner($path)
    {
        return $this->_get_stat_cache_prop($path, 'uid');
    }

    function filegroup($path)
    {
        return $this->_get_stat_cache_prop($path, 'gid');
    }

    function filesize($path)
    {
        return $this->_get_stat_cache_prop($path, 'size');
    }

    function filetype($path)
    {
        $type = $this->_get_stat_cache_prop($path, 'type');
        if ($type === false) {
            return false;
        }

        switch ($type) {
            case NET_SFTP_TYPE_BLOCK_DEVICE:
                return 'block';
            case NET_SFTP_TYPE_CHAR_DEVICE:
                return 'char';
            case NET_SFTP_TYPE_DIRECTORY:
                return 'dir';
            case NET_SFTP_TYPE_FIFO:
                return 'fifo';
            case NET_SFTP_TYPE_REGULAR:
                return 'file';
            case NET_SFTP_TYPE_SYMLINK:
                return 'link';
            default:
                return false;
        }
    }

    function _get_stat_cache_prop($path, $prop)
    {
        return $this->_get_xstat_cache_prop($path, $prop, 'stat');
    }

    function _get_lstat_cache_prop($path, $prop)
    {
        return $this->_get_xstat_cache_prop($path, $prop, 'lstat');
    }

    function _get_xstat_cache_prop($path, $prop, $type)
    {
        if ($this->use_stat_cache) {
            $path = $this->_realpath($path);

            $result = $this->_query_stat_cache($path);

            if (is_object($result) && isset($result->$type)) {
                return $result->{$type}[$prop];
            }
        }

        $result = $this->$type($path);

        if ($result === false || !isset($result[$prop])) {
            return false;
        }

        return $result[$prop];
    }

    function rename($oldname, $newname)
    {
        if (!($this->bitmap & SSH2::MASK_LOGIN)) {
            return false;
        }

        $oldname = $this->_realpath($oldname);
        $newname = $this->_realpath($newname);
        if ($oldname === false || $newname === false) {
            return false;
        }

        // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#section-8.3
        $packet = pack('Na*Na*', strlen($oldname), $oldname, strlen($newname), $newname);
        if (!$this->_send_sftp_packet(NET_SFTP_RENAME, $packet)) {
            return false;
        }

        $response = $this->_get_sftp_packet();
        if ($this->packet_type != NET_SFTP_STATUS) {
            user_error('Expected SSH_FXP_STATUS');
            return false;
        }

        // if $status isn't SSH_FX_OK it's probably SSH_FX_NO_SUCH_FILE or SSH_FX_PERMISSION_DENIED
        extract(unpack('Nstatus', $this->_string_shift($response, 4)));
        if ($status != NET_SFTP_STATUS_OK) {
            $this->_logError($response, $status);
            return false;
        }

        // don't move the stat cache entry over since this operation could very well change the
        // atime and mtime attributes
        //$this->_update_stat_cache($newname, $this->_query_stat_cache($oldname));
        $this->_remove_from_stat_cache($oldname);
        $this->_remove_from_stat_cache($newname);

        return true;
    }

    function _parseAttributes(&$response)
    {
        $attr = array();
        extract(unpack('Nflags', $this->_string_shift($response, 4)));
        // SFTPv4+ have a type field (a byte) that follows the above flag field
        foreach ($this->attributes as $key => $value) {
            switch ($flags & $key) {
                case NET_SFTP_ATTR_SIZE: // 0x00000001
                    // The size attribute is defined as an unsigned 64-bit integer.
                    // The following will use floats on 32-bit platforms, if necessary.
                    // As can be seen in the BigInteger class, floats are generally
                    // IEEE 754 binary64 "double precision" on such platforms and
                    // as such can represent integers of at least 2^50 without loss
                    // of precision. Interpreted in filesize, 2^50 bytes = 1024 TiB.
                    $attr['size'] = hexdec(bin2hex($this->_string_shift($response, 8)));
                    break;
                case NET_SFTP_ATTR_UIDGID: // 0x00000002 (SFTPv3 only)
                    $attr+= unpack('Nuid/Ngid', $this->_string_shift($response, 8));
                    break;
                case NET_SFTP_ATTR_PERMISSIONS: // 0x00000004
                    $attr+= unpack('Npermissions', $this->_string_shift($response, 4));
                    // mode == permissions; permissions was the original array key and is retained for bc purposes.
                    // mode was added because that's the more industry standard terminology
                    $attr+= array('mode' => $attr['permissions']);
                    $fileType = $this->_parseMode($attr['permissions']);
                    if ($fileType !== false) {
                        $attr+= array('type' => $fileType);
                    }
                    break;
                case NET_SFTP_ATTR_ACCESSTIME: // 0x00000008
                    $attr+= unpack('Natime/Nmtime', $this->_string_shift($response, 8));
                    break;
                case NET_SFTP_ATTR_EXTENDED: // 0x80000000
                    extract(unpack('Ncount', $this->_string_shift($response, 4)));
                    for ($i = 0; $i < $count; $i++) {
                        extract(unpack('Nlength', $this->_string_shift($response, 4)));
                        $key = $this->_string_shift($response, $length);
                        extract(unpack('Nlength', $this->_string_shift($response, 4)));
                        $attr[$key] = $this->_string_shift($response, $length);
                    }
            }
        }
        return $attr;
    }

    function _parseMode($mode)
    {
        // values come from http://lxr.free-electrons.com/source/include/uapi/linux/stat.h#L12
        // see, also, http://linux.die.net/man/2/stat
        switch ($mode & 0170000) {// ie. 1111 0000 0000 0000
            case 0000000: // no file type specified - figure out the file type using alternative means
                return false;
            case 0040000:
                return NET_SFTP_TYPE_DIRECTORY;
            case 0100000:
                return NET_SFTP_TYPE_REGULAR;
            case 0120000:
                return NET_SFTP_TYPE_SYMLINK;
            // new types introduced in SFTPv5+
            // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-05#section-5.2
            case 0010000: // named pipe (fifo)
                return NET_SFTP_TYPE_FIFO;
            case 0020000: // character special
                return NET_SFTP_TYPE_CHAR_DEVICE;
            case 0060000: // block special
                return NET_SFTP_TYPE_BLOCK_DEVICE;
            case 0140000: // socket
                return NET_SFTP_TYPE_SOCKET;
            case 0160000: // whiteout
                // "SPECIAL should be used for files that are of
                //  a known type which cannot be expressed in the protocol"
                return NET_SFTP_TYPE_SPECIAL;
            default:
                return NET_SFTP_TYPE_UNKNOWN;
        }
    }

    function _parseLongname($longname)
    {
        // http://en.wikipedia.org/wiki/Unix_file_types
        // http://en.wikipedia.org/wiki/Filesystem_permissions#Notation_of_traditional_Unix_permissions
        if (preg_match('#^[^/]([r-][w-][xstST-]){3}#', $longname)) {
            switch ($longname[0]) {
                case '-':
                    return NET_SFTP_TYPE_REGULAR;
                case 'd':
                    return NET_SFTP_TYPE_DIRECTORY;
                case 'l':
                    return NET_SFTP_TYPE_SYMLINK;
                default:
                    return NET_SFTP_TYPE_SPECIAL;
            }
        }

        return false;
    }

    function _send_sftp_packet($type, $data)
    {
        $packet = $this->request_id !== false ?
            pack('NCNa*', strlen($data) + 5, $type, $this->request_id, $data) :
            pack('NCa*',  strlen($data) + 1, $type, $data);

        $start = strtok(microtime(), ' ') + strtok(''); // http://php.net/microtime#61838
        $result = $this->_send_channel_packet(self::CHANNEL, $packet);
        $stop = strtok(microtime(), ' ') + strtok('');

        if (defined('NET_SFTP_LOGGING')) {
            $packet_type = '-> ' . $this->packet_types[$type] .
                           ' (' . round($stop - $start, 4) . 's)';
            if (NET_SFTP_LOGGING == NET_SFTP_LOG_REALTIME) {
                echo "<pre>\r\n" . $this->_format_log(array($data), array($packet_type)) . "\r\n</pre>\r\n";
                flush();
                ob_flush();
            } else {
                $this->packet_type_log[] = $packet_type;
                if (NET_SFTP_LOGGING == NET_SFTP_LOG_COMPLEX) {
                    $this->packet_log[] = $data;
                }
            }
        }

        return $result;
    }

    function _get_sftp_packet()
    {
        $this->curTimeout = false;

        $start = strtok(microtime(), ' ') + strtok(''); // http://php.net/microtime#61838

        // SFTP packet length
        while (strlen($this->packet_buffer) < 4) {
            $temp = $this->_get_channel_packet(self::CHANNEL);
            if (is_bool($temp)) {
                $this->packet_type = false;
                $this->packet_buffer = '';
                return false;
            }
            $this->packet_buffer.= $temp;
        }
        extract(unpack('Nlength', $this->_string_shift($this->packet_buffer, 4)));
        $tempLength = $length;
        $tempLength-= strlen($this->packet_buffer);

        // SFTP packet type and data payload
        while ($tempLength > 0) {
            $temp = $this->_get_channel_packet(self::CHANNEL);
            if (is_bool($temp)) {
                $this->packet_type = false;
                $this->packet_buffer = '';
                return false;
            }
            $this->packet_buffer.= $temp;
            $tempLength-= strlen($temp);
        }

        $stop = strtok(microtime(), ' ') + strtok('');

        $this->packet_type = ord($this->_string_shift($this->packet_buffer));

        if ($this->request_id !== false) {
            $this->_string_shift($this->packet_buffer, 4); // remove the request id
            $length-= 5; // account for the request id and the packet type
        } else {
            $length-= 1; // account for the packet type
        }

        $packet = $this->_string_shift($this->packet_buffer, $length);

        if (defined('NET_SFTP_LOGGING')) {
            $packet_type = '<- ' . $this->packet_types[$this->packet_type] .
                           ' (' . round($stop - $start, 4) . 's)';
            if (NET_SFTP_LOGGING == NET_SFTP_LOG_REALTIME) {
                echo "<pre>\r\n" . $this->_format_log(array($packet), array($packet_type)) . "\r\n</pre>\r\n";
                flush();
                ob_flush();
            } else {
                $this->packet_type_log[] = $packet_type;
                if (NET_SFTP_LOGGING == NET_SFTP_LOG_COMPLEX) {
                    $this->packet_log[] = $packet;
                }
            }
        }

        return $packet;
    }

    function getSFTPLog()
    {
        if (!defined('NET_SFTP_LOGGING')) {
            return false;
        }

        switch (NET_SFTP_LOGGING) {
            case NET_SFTP_LOG_COMPLEX:
                return $this->_format_log($this->packet_log, $this->packet_type_log);
                break;
            //case NET_SFTP_LOG_SIMPLE:
            default:
                return $this->packet_type_log;
        }
    }

    function getSFTPErrors()
    {
        return $this->sftp_errors;
    }

    function getLastSFTPError()
    {
        return count($this->sftp_errors) ? $this->sftp_errors[count($this->sftp_errors) - 1] : '';
    }

    function getSupportedVersions()
    {
        $temp = array('version' => $this->version);
        if (isset($this->extensions['versions'])) {
            $temp['extensions'] = $this->extensions['versions'];
        }
        return $temp;
    }

    function _disconnect($reason)
    {
        $this->pwd = false;
        parent::_disconnect($reason);
    }
}