Module Lwt_engine

Lwt unix main loop engine

Events

type event

Type of events. An event represent a callback registered to be called when some event occurs.

val stop_event : event -> unit

stop_event event stops the given event.

val fake_event : event

Event which does nothing when stopped.

Event loop functions

val iter : bool -> unit

iter block performs one iteration of the main loop. If block is true the function must block until one event becomes available, otherwise it should just check for available events and return immediately.

val on_readable : Unix.file_descr -> (event -> unit) -> event

on_readable fd f calls f each time fd becomes readable.

val on_writable : Unix.file_descr -> (event -> unit) -> event

on_readable fd f calls f each time fd becomes writable.

val on_timer : float -> bool -> (event -> unit) -> event

on_timer delay repeat f calls f one time after delay seconds. If repeat is true then f is called each delay seconds, otherwise it is called only one time.

val readable_count : unit -> int

Returns the number of events waiting for a file descriptor to become readable.

val writable_count : unit -> int

Returns the number of events waiting for a file descriptor to become writable.

val timer_count : unit -> int

Returns the number of registered timers.

val fake_io : Unix.file_descr -> unit

Simulates activity on the given file descriptor.

val fork : unit -> unit

Called internally by Lwt_unix.fork to make sure we don't get strange behaviour

val forwards_signal : int -> bool

forwards_signal signum is true if the engine will call Lwt_unix.handle_signal when signal signum occurs. In this case, Lwt will not install its own signal handler.

Normally, this just returns false, but when Lwt is used in combination with other IO libraries, this allows sharing e.g. the SIGCHLD handler.

Engines

An engine represents a set of functions used to register different kinds of callbacks for different kinds of events.

class virtual abstract : object ... end

Abstract class for engines.

class type t = object ... end

Type of engines.

Predefined engines

type ev_loop
module Ev_backend : sig ... end

Type of libev loops.

class libev : ?backend:Ev_backend.t -> unit -> object ... end

Engine based on libev. If not compiled with libev support, the creation of the class will raise Lwt_sys.Not_available.

class select : t

Engine based on Unix.select.

class virtual select_based : object ... end

Abstract class for engines based on a select-like function.

class virtual poll_based : object ... end

Abstract class for engines based on a poll-like function.

The current engine

val get : unit -> t

get () returns the engine currently in use.

val set : ?transfer:bool -> ?destroy:bool -> t -> unit

set ?transfer ?destroy engine replaces the current engine by the given one.

If transfer is true (the default) all events from the current engine are transferred to the new one.

If destroy is true (the default) then the current engine is destroyed before being replaced.

module Versioned : sig ... end