Module Lwt_main

module Lwt_main: sig .. end

Main loop and event queue

This module controls the ``main-loop'' of Lwt.

val run : 'a Lwt.t -> 'a

run t calls the Lwt scheduler repeatedly until t terminates, then returns the value returned by the thread. It t fails with an exception, this exception is raised.

Note that you should avoid using run inside threads

The calling threads will not resume before run returns.
Successive invocations of run are serialized: an invocation of run will not terminate before all subsequent invocations are terminated.

val exit_hooks : (unit -> unit Lwt.t) Lwt_sequence.t

Sets of functions executed just before the program exit.

Notes:

each hook is called exactly one time
exceptions raised by hooks are ignored

val at_exit : (unit -> unit Lwt.t) -> unit

at_exit hook adds hook at the left of exit_hooks

Low-level control of event loop

The rest of this file is for advanced users. You must have a good understanding on how Lwt works to use it.

This part has two purpose:

integration of external libraries which are not ``Lwt-aware'' but are ``main-loop'' aware, or more generally which support asynchronous IOs.
replace the default main-loop implementation (which is just a wrapper around select) by another one.

Note that Lwt.wakeup_paused must be called before collecting sources of event and before doing the blocking select or equivalent.

type fd_set = Unix.file_descr list

A set of file-descriptors

type current_time = float Lazy.t

The current time. It is a lazy value to avoid a call to Unix.gettimeofday if not needed.

type select = fd_set ->
       fd_set ->
       fd_set ->
       float option ->
       current_time * fd_set * fd_set * fd_set

Type of a select-like function

val select_filters : (current_time -> select -> select) Lwt_sequence.t

The set of all select filters.

val apply_filters : select -> select

apply_filters select apply all the filters on the given select function.

val default_select : select

The default select function. It uses Unix.select.

val default_iteration : unit -> unit

The default iteration function. It just apply all select filters on default_select, the, call the resulting select function.

val main_loop_iteration : (unit -> unit) Pervasives.ref

The function doing one step of the main loop.

Utils

val min_timeout : float option -> float option -> float option

min_timeout a b returns the smallest timeout of two timeouts.