lib/dirio.js
function _pipe(out, callback, err, iresult) {
  if (err) return callback(err);
  out(iresult, callback);
}
function _pipe(out, callback, err, iresult) {
  if (err) return callback(err);
  out(iresult, callback);
}
function _pipe ( out , callback , err , iresult ) { if ( err ) return callback ( err ) ; out ( iresult , callback ) ; }
Used to pipe input operation to output operation.
@param {Function} out - Output operation.
@param {Function} callback - Callback that expects only
a possible error.
@param {*} err - Possible error passed by caller.
@param {Object} iresult - Result of the input operation.
Used to pipe input operation to output operation .