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 = ( $source === $dest ) ? true : 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 = ( $source === $dest ) ? true : 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
    }

    public 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(
        FSFileBackend $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 $e ) { // bad permissions? deleted?
            throw new FileBackendError( "File iterator gave UnexpectedValueException." );
        }
        ++$this->pos;
    }

    public function rewind() {
        $this->pos = 0;
        try {
            $this->iter->rewind();
            $this->filterViaNext();
        } catch ( UnexpectedValueException $e ) { // bad permissions? deleted?
            throw new FileBackendError( "File iterator gave UnexpectedValueException." );
        }
    }

    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;
            }
        }
    }
}