FSFileBackend.php

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<?php
class FSFileBackend extends FileBackendStore {
        protected $basePath; // string; directory holding the container directories
        protected $containerPaths = array(); // for custom container paths
        protected $fileMode; // integer; file permission mode
        protected $fileOwner; // string; required OS username to own files
        protected $currentUser; // string; OS username running this script

        protected $hadWarningErrors = array();

        public function __construct( array $config ) {
                parent::__construct( $config );

                // Remove any possible trailing slash from directories
                if ( isset( $config['basePath'] ) ) {
                        $this->basePath = rtrim( $config['basePath'], '/' ); // remove trailing slash
                } else {
                        $this->basePath = null; // none; containers must have explicit paths
                }

                if ( isset( $config['containerPaths'] ) ) {
                        $this->containerPaths = (array)$config['containerPaths'];
                        foreach ( $this->containerPaths as &$path ) {
                                $path = rtrim( $path, '/' ); // remove trailing slash
                        }
                }

                $this->fileMode = isset( $config['fileMode'] ) ? $config['fileMode'] : 0644;
                if ( isset( $config['fileOwner'] ) && function_exists( 'posix_getuid' ) ) {
                        $this->fileOwner = $config['fileOwner'];
                        $info = posix_getpwuid( posix_getuid() );
                        $this->currentUser = $info['name']; // cache this, assuming it doesn't change
                }
        }

        protected function resolveContainerPath( $container, $relStoragePath ) {
                // Check that container has a root directory
                if ( isset( $this->containerPaths[$container] ) || isset( $this->basePath ) ) {
                        // Check for sane relative paths (assume the base paths are OK)
                        if ( $this->isLegalRelPath( $relStoragePath ) ) {
                                return $relStoragePath;
                        }
                }
                return null;
        }

        protected function isLegalRelPath( $path ) {
                // Check for file names longer than 255 chars
                if ( preg_match( '![^/]{256}!', $path ) ) { // ext3/NTFS
                        return false;
                }
                if ( wfIsWindows() ) { // NTFS
                        return !preg_match( '![:*?"<>|]!', $path );
                } else {
                        return true;
                }
        }

        protected function containerFSRoot( $shortCont, $fullCont ) {
                if ( isset( $this->containerPaths[$shortCont] ) ) {
                        return $this->containerPaths[$shortCont];
                } elseif ( isset( $this->basePath ) ) {
                        return "{$this->basePath}/{$fullCont}";
                }
                return null; // no container base path defined
        }

        protected function resolveToFSPath( $storagePath ) {
                list( $fullCont, $relPath ) = $this->resolveStoragePathReal( $storagePath );
                if ( $relPath === null ) {
                        return null; // invalid
                }
                list( , $shortCont, ) = FileBackend::splitStoragePath( $storagePath );
                $fsPath = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
                if ( $relPath != '' ) {
                        $fsPath .= "/{$relPath}";
                }
                return $fsPath;
        }

        public function isPathUsableInternal( $storagePath ) {
                $fsPath = $this->resolveToFSPath( $storagePath );
                if ( $fsPath === null ) {
                        return false; // invalid
                }
                $parentDir = dirname( $fsPath );

                if ( file_exists( $fsPath ) ) {
                        $ok = is_file( $fsPath ) && is_writable( $fsPath );
                } else {
                        $ok = is_dir( $parentDir ) && is_writable( $parentDir );
                }

                if ( $this->fileOwner !== null && $this->currentUser !== $this->fileOwner ) {
                        $ok = false;
                        trigger_error( __METHOD__ . ": PHP process owner is not '{$this->fileOwner}'." );
                }

                return $ok;
        }

        protected function doCreateInternal( array $params ) {
                $status = Status::newGood();

                $dest = $this->resolveToFSPath( $params['dst'] );
                if ( $dest === null ) {
                        $status->fatal( 'backend-fail-invalidpath', $params['dst'] );
                        return $status;
                }

                if ( !empty( $params['async'] ) ) { // deferred
                        $tempFile = TempFSFile::factory( 'create_', 'tmp' );
                        if ( !$tempFile ) {
                                $status->fatal( 'backend-fail-create', $params['dst'] );
                                return $status;
                        }
                        $this->trapWarnings();
                        $bytes = file_put_contents( $tempFile->getPath(), $params['content'] );
                        $this->untrapWarnings();
                        if ( $bytes === false ) {
                                $status->fatal( 'backend-fail-create', $params['dst'] );
                                return $status;
                        }
                        $cmd = implode( ' ', array(
                                wfIsWindows() ? 'COPY /B /Y' : 'cp', // (binary, overwrite)
                                wfEscapeShellArg( $this->cleanPathSlashes( $tempFile->getPath() ) ),
                                wfEscapeShellArg( $this->cleanPathSlashes( $dest ) )
                        ) );
                        $status->value = new FSFileOpHandle( $this, $params, 'Create', $cmd, $dest );
                        $tempFile->bind( $status->value );
                } else { // immediate write
                        $this->trapWarnings();
                        $bytes = file_put_contents( $dest, $params['content'] );
                        $this->untrapWarnings();
                        if ( $bytes === false ) {
                                $status->fatal( 'backend-fail-create', $params['dst'] );
                                return $status;
                        }
                        $this->chmod( $dest );
                }

                return $status;
        }

        protected function _getResponseCreate( $errors, Status $status, array $params, $cmd ) {
                if ( $errors !== '' && !( wfIsWindows() && $errors[0] === " " ) ) {
                        $status->fatal( 'backend-fail-create', $params['dst'] );
                        trigger_error( "$cmd\n$errors", E_USER_WARNING ); // command output
                }
        }

        protected function doStoreInternal( array $params ) {
                $status = Status::newGood();

                $dest = $this->resolveToFSPath( $params['dst'] );
                if ( $dest === null ) {
                        $status->fatal( 'backend-fail-invalidpath', $params['dst'] );
                        return $status;
                }

                if ( !empty( $params['async'] ) ) { // deferred
                        $cmd = implode( ' ', array(
                                wfIsWindows() ? 'COPY /B /Y' : 'cp', // (binary, overwrite)
                                wfEscapeShellArg( $this->cleanPathSlashes( $params['src'] ) ),
                                wfEscapeShellArg( $this->cleanPathSlashes( $dest ) )
                        ) );
                        $status->value = new FSFileOpHandle( $this, $params, 'Store', $cmd, $dest );
                } else { // immediate write
                        $this->trapWarnings();
                        $ok = copy( $params['src'], $dest );
                        $this->untrapWarnings();
                        // In some cases (at least over NFS), copy() returns true when it fails
                        if ( !$ok || ( filesize( $params['src'] ) !== filesize( $dest ) ) ) {
                                if ( $ok ) { // PHP bug
                                        unlink( $dest ); // remove broken file
                                        trigger_error( __METHOD__ . ": copy() failed but returned true." );
                                }
                                $status->fatal( 'backend-fail-store', $params['src'], $params['dst'] );
                                return $status;
                        }
                        $this->chmod( $dest );
                }

                return $status;
        }

        protected function _getResponseStore( $errors, Status $status, array $params, $cmd ) {
                if ( $errors !== '' && !( wfIsWindows() && $errors[0] === " " ) ) {
                        $status->fatal( 'backend-fail-store', $params['src'], $params['dst'] );
                        trigger_error( "$cmd\n$errors", E_USER_WARNING ); // command output
                }
        }

        protected function doCopyInternal( array $params ) {
                $status = Status::newGood();

                $source = $this->resolveToFSPath( $params['src'] );
                if ( $source === null ) {
                        $status->fatal( 'backend-fail-invalidpath', $params['src'] );
                        return $status;
                }

                $dest = $this->resolveToFSPath( $params['dst'] );
                if ( $dest === null ) {
                        $status->fatal( 'backend-fail-invalidpath', $params['dst'] );
                        return $status;
                }

                if ( !is_file( $source ) ) {
                        if ( empty( $params['ignoreMissingSource'] ) ) {
                                $status->fatal( 'backend-fail-copy', $params['src'] );
                        }
                        return $status; // do nothing; either OK or bad status
                }

                if ( !empty( $params['async'] ) ) { // deferred
                        $cmd = implode( ' ', array(
                                wfIsWindows() ? 'COPY /B /Y' : 'cp', // (binary, overwrite)
                                wfEscapeShellArg( $this->cleanPathSlashes( $source ) ),
                                wfEscapeShellArg( $this->cleanPathSlashes( $dest ) )
                        ) );
                        $status->value = new FSFileOpHandle( $this, $params, 'Copy', $cmd, $dest );
                } else { // immediate write
                        $this->trapWarnings();
                        $ok = copy( $source, $dest );
                        $this->untrapWarnings();
                        // In some cases (at least over NFS), copy() returns true when it fails
                        if ( !$ok || ( filesize( $source ) !== filesize( $dest ) ) ) {
                                if ( $ok ) { // PHP bug
                                        $this->trapWarnings();
                                        unlink( $dest ); // remove broken file
                                        $this->untrapWarnings();
                                        trigger_error( __METHOD__ . ": copy() failed but returned true." );
                                }
                                $status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
                                return $status;
                        }
                        $this->chmod( $dest );
                }

                return $status;
        }

        protected function _getResponseCopy( $errors, Status $status, array $params, $cmd ) {
                if ( $errors !== '' && !( wfIsWindows() && $errors[0] === " " ) ) {
                        $status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
                        trigger_error( "$cmd\n$errors", E_USER_WARNING ); // command output
                }
        }

        protected function doMoveInternal( array $params ) {
                $status = Status::newGood();

                $source = $this->resolveToFSPath( $params['src'] );
                if ( $source === null ) {
                        $status->fatal( 'backend-fail-invalidpath', $params['src'] );
                        return $status;
                }

                $dest = $this->resolveToFSPath( $params['dst'] );
                if ( $dest === null ) {
                        $status->fatal( 'backend-fail-invalidpath', $params['dst'] );
                        return $status;
                }

                if ( !is_file( $source ) ) {
                        if ( empty( $params['ignoreMissingSource'] ) ) {
                                $status->fatal( 'backend-fail-move', $params['src'] );
                        }
                        return $status; // do nothing; either OK or bad status
                }

                if ( !empty( $params['async'] ) ) { // deferred
                        $cmd = implode( ' ', array(
                                wfIsWindows() ? 'MOVE /Y' : 'mv', // (overwrite)
                                wfEscapeShellArg( $this->cleanPathSlashes( $source ) ),
                                wfEscapeShellArg( $this->cleanPathSlashes( $dest ) )
                        ) );
                        $status->value = new FSFileOpHandle( $this, $params, 'Move', $cmd );
                } else { // immediate write
                        $this->trapWarnings();
                        $ok = rename( $source, $dest );
                        $this->untrapWarnings();
                        clearstatcache(); // file no longer at source
                        if ( !$ok ) {
                                $status->fatal( 'backend-fail-move', $params['src'], $params['dst'] );
                                return $status;
                        }
                }

                return $status;
        }

        protected function _getResponseMove( $errors, Status $status, array $params, $cmd ) {
                if ( $errors !== '' && !( wfIsWindows() && $errors[0] === " " ) ) {
                        $status->fatal( 'backend-fail-move', $params['src'], $params['dst'] );
                        trigger_error( "$cmd\n$errors", E_USER_WARNING ); // command output
                }
        }

        protected function doDeleteInternal( array $params ) {
                $status = Status::newGood();

                $source = $this->resolveToFSPath( $params['src'] );
                if ( $source === null ) {
                        $status->fatal( 'backend-fail-invalidpath', $params['src'] );
                        return $status;
                }

                if ( !is_file( $source ) ) {
                        if ( empty( $params['ignoreMissingSource'] ) ) {
                                $status->fatal( 'backend-fail-delete', $params['src'] );
                        }
                        return $status; // do nothing; either OK or bad status
                }

                if ( !empty( $params['async'] ) ) { // deferred
                        $cmd = implode( ' ', array(
                                wfIsWindows() ? 'DEL' : 'unlink',
                                wfEscapeShellArg( $this->cleanPathSlashes( $source ) )
                        ) );
                        $status->value = new FSFileOpHandle( $this, $params, 'Copy', $cmd );
                } else { // immediate write
                        $this->trapWarnings();
                        $ok = unlink( $source );
                        $this->untrapWarnings();
                        if ( !$ok ) {
                                $status->fatal( 'backend-fail-delete', $params['src'] );
                                return $status;
                        }
                }

                return $status;
        }

        protected function _getResponseDelete( $errors, Status $status, array $params, $cmd ) {
                if ( $errors !== '' && !( wfIsWindows() && $errors[0] === " " ) ) {
                        $status->fatal( 'backend-fail-delete', $params['src'] );
                        trigger_error( "$cmd\n$errors", E_USER_WARNING ); // command output
                }
        }

        protected function doPrepareInternal( $fullCont, $dirRel, array $params ) {
                $status = Status::newGood();
                list( , $shortCont, ) = FileBackend::splitStoragePath( $params['dir'] );
                $contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
                $dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
                $existed = is_dir( $dir ); // already there?
                // Create the directory and its parents as needed...
                $this->trapWarnings();
                if ( !wfMkdirParents( $dir ) ) {
                        $status->fatal( 'directorycreateerror', $params['dir'] ); // fails on races
                } elseif ( !is_writable( $dir ) ) {
                        $status->fatal( 'directoryreadonlyerror', $params['dir'] );
                } elseif ( !is_readable( $dir ) ) {
                        $status->fatal( 'directorynotreadableerror', $params['dir'] );
                }
                $this->untrapWarnings();
                // Respect any 'noAccess' or 'noListing' flags...
                if ( is_dir( $dir ) && !$existed ) {
                        $status->merge( $this->doSecureInternal( $fullCont, $dirRel, $params ) );
                }
                return $status;
        }

        protected function doSecureInternal( $fullCont, $dirRel, array $params ) {
                $status = Status::newGood();
                list( , $shortCont, ) = FileBackend::splitStoragePath( $params['dir'] );
                $contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
                $dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
                // Seed new directories with a blank index.html, to prevent crawling...
                if ( !empty( $params['noListing'] ) && !file_exists( "{$dir}/index.html" ) ) {
                        $this->trapWarnings();
                        $bytes = file_put_contents( "{$dir}/index.html", $this->indexHtmlPrivate() );
                        $this->untrapWarnings();
                        if ( $bytes === false ) {
                                $status->fatal( 'backend-fail-create', $params['dir'] . '/index.html' );
                        }
                }
                // Add a .htaccess file to the root of the container...
                if ( !empty( $params['noAccess'] ) && !file_exists( "{$contRoot}/.htaccess" ) ) {
                        $this->trapWarnings();
                        $bytes = file_put_contents( "{$contRoot}/.htaccess", $this->htaccessPrivate() );
                        $this->untrapWarnings();
                        if ( $bytes === false ) {
                                $storeDir = "mwstore://{$this->name}/{$shortCont}";
                                $status->fatal( 'backend-fail-create', "{$storeDir}/.htaccess" );
                        }
                }
                return $status;
        }

        protected function doPublishInternal( $fullCont, $dirRel, array $params ) {
                $status = Status::newGood();
                list( , $shortCont, ) = FileBackend::splitStoragePath( $params['dir'] );
                $contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
                $dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
                // Unseed new directories with a blank index.html, to allow crawling...
                if ( !empty( $params['listing'] ) && is_file( "{$dir}/index.html" ) ) {
                        $exists = ( file_get_contents( "{$dir}/index.html" ) === $this->indexHtmlPrivate() );
                        $this->trapWarnings();
                        if ( $exists && !unlink( "{$dir}/index.html" ) ) { // reverse secure()
                                $status->fatal( 'backend-fail-delete', $params['dir'] . '/index.html' );
                        }
                        $this->untrapWarnings();
                }
                // Remove the .htaccess file from the root of the container...
                if ( !empty( $params['access'] ) && is_file( "{$contRoot}/.htaccess" ) ) {
                        $exists = ( file_get_contents( "{$contRoot}/.htaccess" ) === $this->htaccessPrivate() );
                        $this->trapWarnings();
                        if ( $exists && !unlink( "{$contRoot}/.htaccess" ) ) { // reverse secure()
                                $storeDir = "mwstore://{$this->name}/{$shortCont}";
                                $status->fatal( 'backend-fail-delete', "{$storeDir}/.htaccess" );
                        }
                        $this->untrapWarnings();
                }
                return $status;
        }

        protected function doCleanInternal( $fullCont, $dirRel, array $params ) {
                $status = Status::newGood();
                list( , $shortCont, ) = FileBackend::splitStoragePath( $params['dir'] );
                $contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
                $dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
                $this->trapWarnings();
                if ( is_dir( $dir ) ) {
                        rmdir( $dir ); // remove directory if empty
                }
                $this->untrapWarnings();
                return $status;
        }

        protected function doGetFileStat( array $params ) {
                $source = $this->resolveToFSPath( $params['src'] );
                if ( $source === null ) {
                        return false; // invalid storage path
                }

                $this->trapWarnings(); // don't trust 'false' if there were errors
                $stat = is_file( $source ) ? stat( $source ) : false; // regular files only
                $hadError = $this->untrapWarnings();

                if ( $stat ) {
                        return array(
                                'mtime' => wfTimestamp( TS_MW, $stat['mtime'] ),
                                'size'  => $stat['size']
                        );
                } elseif ( !$hadError ) {
                        return false; // file does not exist
                } else {
                        return null; // failure
                }
        }

        protected function doClearCache( array $paths = null ) {
                clearstatcache(); // clear the PHP file stat cache
        }

        protected function doDirectoryExists( $fullCont, $dirRel, array $params ) {
                list( , $shortCont, ) = FileBackend::splitStoragePath( $params['dir'] );
                $contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
                $dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;

                $this->trapWarnings(); // don't trust 'false' if there were errors
                $exists = is_dir( $dir );
                $hadError = $this->untrapWarnings();

                return $hadError ? null : $exists;
        }

        public function getDirectoryListInternal( $fullCont, $dirRel, array $params ) {
                list( , $shortCont, ) = FileBackend::splitStoragePath( $params['dir'] );
                $contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
                $dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
                $exists = is_dir( $dir );
                if ( !$exists ) {
                        wfDebug( __METHOD__ . "() given directory does not exist: '$dir'\n" );
                        return array(); // nothing under this dir
                } elseif ( !is_readable( $dir ) ) {
                        wfDebug( __METHOD__ . "() given directory is unreadable: '$dir'\n" );
                        return null; // bad permissions?
                }
                return new FSFileBackendDirList( $dir, $params );
        }

        public function getFileListInternal( $fullCont, $dirRel, array $params ) {
                list( , $shortCont, ) = FileBackend::splitStoragePath( $params['dir'] );
                $contRoot = $this->containerFSRoot( $shortCont, $fullCont ); // must be valid
                $dir = ( $dirRel != '' ) ? "{$contRoot}/{$dirRel}" : $contRoot;
                $exists = is_dir( $dir );
                if ( !$exists ) {
                        wfDebug( __METHOD__ . "() given directory does not exist: '$dir'\n" );
                        return array(); // nothing under this dir
                } elseif ( !is_readable( $dir ) ) {
                        wfDebug( __METHOD__ . "() given directory is unreadable: '$dir'\n" );
                        return null; // bad permissions?
                }
                return new FSFileBackendFileList( $dir, $params );
        }

        protected function doGetLocalReferenceMulti( array $params ) {
                $fsFiles = array(); // (path => FSFile)

                foreach ( $params['srcs'] as $src ) {
                        $source = $this->resolveToFSPath( $src );
                        if ( $source === null || !is_file( $source ) ) {
                                $fsFiles[$src] = null; // invalid path or file does not exist
                        } else {
                                $fsFiles[$src] = new FSFile( $source );
                        }
                }

                return $fsFiles;
        }

        protected function doGetLocalCopyMulti( array $params ) {
                $tmpFiles = array(); // (path => TempFSFile)

                foreach ( $params['srcs'] as $src ) {
                        $source = $this->resolveToFSPath( $src );
                        if ( $source === null ) {
                                $tmpFiles[$src] = null; // invalid path
                        } else {
                                // Create a new temporary file with the same extension...
                                $ext = FileBackend::extensionFromPath( $src );
                                $tmpFile = TempFSFile::factory( 'localcopy_', $ext );
                                if ( !$tmpFile ) {
                                        $tmpFiles[$src] = null;
                                } else {
                                        $tmpPath = $tmpFile->getPath();
                                        // Copy the source file over the temp file
                                        $this->trapWarnings();
                                        $ok = copy( $source, $tmpPath );
                                        $this->untrapWarnings();
                                        if ( !$ok ) {
                                                $tmpFiles[$src] = null;
                                        } else {
                                                $this->chmod( $tmpPath );
                                                $tmpFiles[$src] = $tmpFile;
                                        }
                                }
                        }
                }

                return $tmpFiles;
        }

        protected function directoriesAreVirtual() {
                return false;
        }

        protected function doExecuteOpHandlesInternal( array $fileOpHandles ) {
                $statuses = array();

                $pipes = array();
                foreach ( $fileOpHandles as $index => $fileOpHandle ) {
                        $pipes[$index] = popen( "{$fileOpHandle->cmd} 2>&1", 'r' );
                }

                $errs = array();
                foreach ( $pipes as $index => $pipe ) {
                        // Result will be empty on success in *NIX. On Windows,
                        // it may be something like "        1 file(s) [copied|moved].".
                        $errs[$index] = stream_get_contents( $pipe );
                        fclose( $pipe );
                }

                foreach ( $fileOpHandles as $index => $fileOpHandle ) {
                        $status = Status::newGood();
                        $function = '_getResponse' . $fileOpHandle->call;
                        $this->$function( $errs[$index], $status, $fileOpHandle->params, $fileOpHandle->cmd );
                        $statuses[$index] = $status;
                        if ( $status->isOK() && $fileOpHandle->chmodPath ) {
                                $this->chmod( $fileOpHandle->chmodPath );
                        }
                }

                clearstatcache(); // files changed
                return $statuses;
        }

        protected function chmod( $path ) {
                $this->trapWarnings();
                $ok = chmod( $path, $this->fileMode );
                $this->untrapWarnings();

                return $ok;
        }

        protected function indexHtmlPrivate() {
                return '';
        }

        protected function htaccessPrivate() {
                return "Deny from all\n";
        }

        protected function cleanPathSlashes( $path ) {
                return wfIsWindows() ? strtr( $path, '/', '\\' ) : $path;
        }

        protected function trapWarnings() {
                $this->hadWarningErrors[] = false; // push to stack
                set_error_handler( array( $this, 'handleWarning' ), E_WARNING );
        }

        protected function untrapWarnings() {
                restore_error_handler(); // restore previous handler
                return array_pop( $this->hadWarningErrors ); // pop from stack
        }

        private function handleWarning( $errno, $errstr ) {
                wfDebugLog( 'FSFileBackend', $errstr ); // more detailed error logging
                $this->hadWarningErrors[count( $this->hadWarningErrors ) - 1] = true;
                return true; // suppress from PHP handler
        }
}

class FSFileOpHandle extends FileBackendStoreOpHandle {
        public $cmd; // string; shell command
        public $chmodPath; // string; file to chmod

        public function __construct( $backend, array $params, $call, $cmd, $chmodPath = null ) {
                $this->backend = $backend;
                $this->params = $params;
                $this->call = $call;
                $this->cmd = $cmd;
                $this->chmodPath = $chmodPath;
        }
}

abstract class FSFileBackendList implements Iterator {
        protected $iter;
        protected $suffixStart; // integer
        protected $pos = 0; // integer
        protected $params = array();

        public function __construct( $dir, array $params ) {
                $path = realpath( $dir ); // normalize
                if( $path === false ) {
                        $path = $dir;
                }
                $this->suffixStart = strlen( $path ) + 1; // size of "path/to/dir/"
                $this->params = $params;

                try {
                        $this->iter = $this->initIterator( $path );
                } catch ( UnexpectedValueException $e ) {
                        $this->iter = null; // bad permissions? deleted?
                }
        }

        protected function initIterator( $dir ) {
                if ( !empty( $this->params['topOnly'] ) ) { // non-recursive
                        # Get an iterator that will get direct sub-nodes
                        return new DirectoryIterator( $dir );
                } else { // recursive
                        # Get an iterator that will return leaf nodes (non-directories)
                        # RecursiveDirectoryIterator extends FilesystemIterator.
                        # FilesystemIterator::SKIP_DOTS default is inconsistent in PHP 5.3.x.
                        $flags = FilesystemIterator::CURRENT_AS_SELF | FilesystemIterator::SKIP_DOTS;
                        return new RecursiveIteratorIterator(
                                new RecursiveDirectoryIterator( $dir, $flags ),
                                RecursiveIteratorIterator::CHILD_FIRST // include dirs
                        );
                }
        }

        public function key() {
                return $this->pos;
        }

        public function current() {
                return $this->getRelPath( $this->iter->current()->getPathname() );
        }

        public function next() {
                try {
                        $this->iter->next();
                        $this->filterViaNext();
                } catch ( UnexpectedValueException $e ) {
                        $this->iter = null;
                }
                ++$this->pos;
        }

        public function rewind() {
                $this->pos = 0;
                try {
                        $this->iter->rewind();
                        $this->filterViaNext();
                } catch ( UnexpectedValueException $e ) {
                        $this->iter = null;
                }
        }

        public function valid() {
                return $this->iter && $this->iter->valid();
        }

        protected function filterViaNext() {}

        protected function getRelPath( $dir ) {
                $path = realpath( $dir );
                if( $path === false ) {
                        $path = $dir;
                }
                return strtr( substr( $path, $this->suffixStart ), '\\', '/' );
        }
}

class FSFileBackendDirList extends FSFileBackendList {
        protected function filterViaNext() {
                while ( $this->iter->valid() ) {
                        if ( $this->iter->current()->isDot() || !$this->iter->current()->isDir() ) {
                                $this->iter->next(); // skip non-directories and dot files
                        } else {
                                break;
                        }
                }
        }
}

class FSFileBackendFileList extends FSFileBackendList {
        protected function filterViaNext() {
                while ( $this->iter->valid() ) {
                        if ( !$this->iter->current()->isFile() ) {
                                $this->iter->next(); // skip non-files and dot files
                        } else {
                                break;
                        }
                }
        }
}