function onDir( error, files ) {
	var fpath;
	var f;
	var i;
	if ( error ) {
		debug( 'Encountered an error when attempting to read directory contents: %s', error.message );
		throw error;
	}
	debug( 'Successfully read directory contents: %s', files.join( ' ' ) );
	NUM_FILES = files.length;
	for ( i = 0; i < files.length; i++ ) {
		f = files[ i ];
		if ( extname( f ) === RAW_EXTNAME && RE.test( f ) ) {
			fpath = join( dataDir, f );
			debug( 'Possible raw data file: %s', fpath );
			fs.stat( fpath, onStatClbk( files[ i ] ) );
		} else {
			NUM_FILES -= 1;
		}
	}
}
Callback invoked upon reading a directory.

@private
@param {(Error|null)} error - error object
@param {StringArray} files - file list