PipeWire: spa_loop_control_methods Struct Reference

PipeWire 1.4.9

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spa_loop_control_methods Struct Reference
SPA » Support » Loop

Control an event loop. More...

`#include <spa/support/loop.h>`

## Data Fields
uint32_t | version
int(* | get_fd )(void *object)
| get the loop fd
void(* | add_hook )(void *object, struct spa_hook *hook, const struct spa_loop_control_hooks *hooks, void *data)
| Add a hook.
void(* | enter )(void *object)
| Enter a loop.
void(* | leave )(void *object)
| Leave a loop.
int(* | iterate )(void *object, int timeout)
| Perform one iteration of the loop.
int(* | check )(void *object)
| Check context of the loop.

## Detailed Description

Control an event loop.

The event loop control function provide API to run the event loop.

The below (pseudo)code is a minimal example outlining the use of the loop control:

spa_loop_control_enter(loop);
while (running) {
spa_loop_control_iterate(loop, -1);
}
spa_loop_control_leave(loop);
spa_loop_control_enter
SPA_API_LOOP void spa_loop_control_enter(struct spa_loop_control *object)
Definition loop.h:313
spa_loop_control_iterate
SPA_API_LOOP int spa_loop_control_iterate(struct spa_loop_control *object, int timeout)
Definition loop.h:321
spa_loop_control_leave
SPA_API_LOOP void spa_loop_control_leave(struct spa_loop_control *object)
Definition loop.h:317

It is also possible to add the loop to an existing event loop by using the spa_loop_control_get_fd() call. This fd will become readable when activity has been detected on the sources in the loop. spa_loop_control_iterate() with a 0 timeout should be called to process the pending sources.

spa_loop_control_enter() and spa_loop_control_leave() should be called once from the thread that will run the iterate() function.

## Field Documentation

## ◆ version

uint32_t spa_loop_control_methods::version

## ◆ get_fd

int(* spa_loop_control_methods::get_fd) (void *object)

get the loop fd

Parameters

  object | the control to query

Get the fd of this loop control. This fd will be readable when a source in the loop has activity. The user should call iterate() with a 0 timeout to schedule one iteration of the loop and dispatch the sources.

Returns
  the fd of the loop

## ◆ add_hook

void(* spa_loop_control_methods::add_hook) (void *object, struct spa_hook *hook, const struct spa_loop_control_hooks *hooks, void *data)

Add a hook.

Parameters

  object | the control to change
  hooks | the hooks to add

Adds hooks to the loop controlled by ctrl.

## ◆ enter

void(* spa_loop_control_methods::enter) (void *object)

Enter a loop.

Parameters

  object | the control

This function should be called before calling iterate and is typically used to capture the thread that this loop will run in. It should ideally be called once from the thread that will run the loop.

## ◆ leave

void(* spa_loop_control_methods::leave) (void *object)

Leave a loop.

Parameters

  object | the control

It should ideally be called once after calling iterate when the loop will no longer be iterated from the thread that called enter().

## ◆ iterate

int(* spa_loop_control_methods::iterate) (void *object, int timeout)

Perform one iteration of the loop.

Parameters

  ctrl | the control
  timeout | an optional timeout in milliseconds. 0 for no timeout, -1 for infinite timeout.

This function will block up to timeout milliseconds and then dispatch the fds with activity. The number of dispatched fds is returned.

## ◆ check

int(* spa_loop_control_methods::check) (void *object)

Check context of the loop.

Parameters

  ctrl | the control

This function will check if the current thread is currently the one that did the enter call. Since version 1:1.

returns 1 on success, 0 or negative errno value on error.

The documentation for this struct was generated from the following file:

- spa/support/loop.h