function onStatClbk( file ) {
	return onStat;

	/**
	* Callback invoked upon reading file stats.
	*
	* @private
	* @param {(Error|null)} error - error object
	* @param {Object} stats object
	*/
	function onStat( error, stats ) {
		var fpath;
		if ( error ) {
			debug( 'Encountered an error when attempting to read file stats: %s', error.message );
			throw error;
		}
		if ( stats.isFile() ) {
			fpath = join( dataDir, file );
			debug( 'Found a raw data file: %s', file );
			readFile( fpath, OPTS, onFileClbk( file ) );
		} else {
			NUM_FILES -= 1;
		}
	}
}
Returns a callback to be invoked upon reading file stats.

@private
@param {string} file - file name
@returns {Callback} callback