Type Alias dispatch_io_handler_t 

pub type dispatch_io_handler_t = *mut DynBlock<dyn Fn(bool, *mut DispatchData, c_int)>;

The prototype of I/O handler blocks for dispatch I/O operations.

Parameter done: A flag indicating whether the operation is complete.

Parameter data: The data object to be handled.

Parameter error: An errno condition for the operation.

See also Apple’s documentation