Module Lwt_engine

Events
Event loop functions
Engines
Predefined engines
The current engine

Instructions: Use this module in your project

In the IDE (CLion, Visual Studio Code, Xcode, etc.) you use for your DkSDK project:

Add the following to your project's dependencies/CMakeLists.txt:

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DkSDKProject_DeclareAvailable(lwt
    CONSTRAINT "= 5.6.1"
    FINDLIBS lwt lwt.unix)
DkSDKProject_MakeAvailable(lwt)

Add the Findlib::lwt library to any desired targets in src/*/CMakeLists.txt:

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target_link_libraries(YourPackage_YourLibraryName
     # ... existing libraries, if any ...
     Findlib::lwt)

Click your IDE's Build button

Not using DkSDK?

FIRST, do one or all of the following:

Run:
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```
opam install lwt.5.6.1
```

Edit your dune-project and add:

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(package
  (name YourExistingPackage)
  (depends
  ; ... existing dependenices ...
  (lwt (>= 5.6.1))))

Then run:

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dune build *.opam # if this fails, run: dune build

Edit your <package>.opam file and add:

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depends: [
  # ... existing dependencies ...
  "lwt" {>= "5.6.1"}
]

Then run:

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opam install . --deps-only

FINALLY, add the lwt.unix library to any desired (library)and/or (executable) targets in your **/dune files:

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(library
  (name YourLibrary)
  ; ... existing library options ...
  (libraries
    ; ... existing libraries ...
    lwt.unix))

(executable
  (name YourExecutable)
  ; ... existing executable options ...
  (libraries
    ; ... existing libraries ...
    lwt.unix))

Events

type event

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

valstop_event :event -> unit

stop_event event stops the given event.

valfake_event :event

Event which does nothing when stopped.

Event loop functions

valiter : ``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.

valon_readable :Unix.file_descr -> ``(event ->unit)``-> event

on_readable fd f calls f each time fd becomes readable.

valon_writable :Unix.file_descr -> ``(event ->unit)``-> event

on_readable fd f calls f each time fd becomes writable.

valon_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.

valreadable_count : ``unit-> int

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

valwritable_count : ``unit-> int

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

valtimer_count : ``unit-> int

Returns the number of registered timers.

valfake_io :Unix.file_descr -> unit

Simulates activity on the given file descriptor.

valfork : ``unit-> unit

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

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

valget : ``unit-> t

get () returns the engine currently in use.

valset : ``?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

More from the DkSDK Book

1. DkSDK
1. 1. Package capnp
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  1. 1. ...
    1. Module Lwt_engine
    1. 1. Module Lwt_engine.Ev_backend
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