pipewire/spa/include/spa/support/loop.h

/* Simple Plugin API */
/* SPDX-FileCopyrightText: Copyright © 2018 Wim Taymans */
/* SPDX-License-Identifier: MIT */

#ifndef SPA_LOOP_H
#define SPA_LOOP_H

#include <errno.h>

#include <spa/utils/defs.h>
#include <spa/utils/hook.h>
#include <spa/support/system.h>

#ifdef __cplusplus
extern "C" {
#endif

#ifndef SPA_API_LOOP
 #ifdef SPA_API_IMPL
  #define SPA_API_LOOP SPA_API_IMPL
 #else
  #define SPA_API_LOOP static inline
 #endif
#endif

/** \defgroup spa_loop Loop
 * Event loop interface
 */

/**
 * \addtogroup spa_loop
 * \{
 */

#define SPA_TYPE_INTERFACE_Loop		SPA_TYPE_INFO_INTERFACE_BASE "Loop"
#define SPA_TYPE_INTERFACE_DataLoop	SPA_TYPE_INFO_INTERFACE_BASE "DataLoop"
#define SPA_VERSION_LOOP		0
struct spa_loop { struct spa_interface iface; };

#define SPA_TYPE_INTERFACE_LoopControl	SPA_TYPE_INFO_INTERFACE_BASE "LoopControl"
#define SPA_VERSION_LOOP_CONTROL	2
struct spa_loop_control { struct spa_interface iface; };

#define SPA_TYPE_INTERFACE_LoopUtils	SPA_TYPE_INFO_INTERFACE_BASE "LoopUtils"
#define SPA_VERSION_LOOP_UTILS		0
struct spa_loop_utils { struct spa_interface iface; };

struct spa_source;

typedef void (*spa_source_func_t) (struct spa_source *source);

struct spa_source {
	struct spa_loop *loop;
	spa_source_func_t func;
	void *data;
	int fd;
	uint32_t mask;
	uint32_t rmask;
	/* private data for the loop implementer */
	void *priv;
};

typedef int (*spa_invoke_func_t) (struct spa_loop *loop,
				  bool async,
				  uint32_t seq,
				  const void *data,
				  size_t size,
				  void *user_data);

/**
 * Register sources and work items to an event loop
 */
struct spa_loop_methods {
	/* the version of this structure. This can be used to expand this
	 * structure in the future */
#define SPA_VERSION_LOOP_METHODS	0
	uint32_t version;

	/** Add a source to the loop. Must be called from the loop's own thread.
	 *
	 * \param[in] object The callbacks data.
	 * \param[in] source The source.
	 * \return 0 on success, negative errno-style value on failure.
	 */
	int (*add_source) (void *object,
			   struct spa_source *source);

	/** Update the source io mask. Must be called from the loop's own thread.
	 *
	 * \param[in] object The callbacks data.
	 * \param[in] source The source.
	 * \return 0 on success, negative errno-style value on failure.
	 */
	int (*update_source) (void *object,
			struct spa_source *source);

	/** Remove a source from the loop. Must be called from the loop's own thread.
	 *
	 * \param[in] object The callbacks data.
	 * \param[in] source The source.
	 * \return 0 on success, negative errno-style value on failure.
	 */
	int (*remove_source) (void *object,
			struct spa_source *source);

	/** Invoke a function in the context of this loop.
	 * May be called from any thread and multiple threads at the same time.
	 *
	 * If called from the loop's thread, all callbacks previously queued with
	 * invoke() will be run synchronously, which might cause unexpected
	 * reentrancy problems.
	 *
	 * \param[in] object The callbacks data.
	 * \param func The function to be invoked.
	 * \param seq An opaque sequence number. This will be made
	 *            available to func.
	 * \param[in] data Data that will be copied into the internal ring buffer and made
	 *             available to func. Because this data is copied, it is okay to
	 *             pass a pointer to a local variable, but do not pass a pointer to
	 *             an object that has identity.
	 * \param size The size of data to copy.
	 * \param block If \true, do not return until func has been called. Otherwise,
	 *              returns immediately. Passing \true can cause a deadlock when
	 *              the calling thread is holding the loop context lock. A blocking
	 *              invoke should never be done from a realtime thread. Also beware
	 *              of blocking invokes between 2 threads as you can easily end up
	 *              in a deadly embrace.
	 * \param user_data An opaque pointer passed to func.
	 * \return `-EPIPE` if the internal ring buffer filled up,
	 *         if block is \false, 0 if seq was SPA_ID_INVALID or
	 *         seq with the ASYNC flag set
	 *         or the return value of func otherwise. */
	int (*invoke) (void *object,
		       spa_invoke_func_t func,
		       uint32_t seq,
		       const void *data,
		       size_t size,
		       bool block,
		       void *user_data);

	/** Call a function with the loop lock acquired
	 * May be called from any thread and multiple threads at the same time.
	 *
	 * \param[in] object The callbacks data.
	 * \param func The function to be called.
	 * \param seq An opaque sequence number. This will be made
	 *            available to func.
	 * \param[in] data Data that will be passed to func.
	 * \param size The size of data.
	 * \param user_data An opaque pointer passed to func.
	 * \return the return value of func. */
	int (*locked) (void *object,
		       spa_invoke_func_t func,
		       uint32_t seq,
		       const void *data,
		       size_t size,
		       void *user_data);
};

SPA_API_LOOP int spa_loop_add_source(struct spa_loop *object, struct spa_source *source)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop, &object->iface, add_source, 0, source);
}
SPA_API_LOOP int spa_loop_update_source(struct spa_loop *object, struct spa_source *source)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop, &object->iface, update_source, 0, source);
}
SPA_API_LOOP int spa_loop_remove_source(struct spa_loop *object, struct spa_source *source)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop, &object->iface, remove_source, 0, source);
}
SPA_API_LOOP int spa_loop_invoke(struct spa_loop *object,
		spa_invoke_func_t func, uint32_t seq, const void *data,
		size_t size, bool block, void *user_data)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop, &object->iface, invoke, 0, func, seq, data,
			size, block, user_data);
}
SPA_API_LOOP int spa_loop_locked(struct spa_loop *object,
		spa_invoke_func_t func, uint32_t seq, const void *data,
		size_t size, void *user_data)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop, &object->iface, locked, 0, func, seq, data,
			size, user_data);
}


/** Control hooks. These hooks can't be removed from their
 *  callbacks and must be removed from a safe place (when the loop
 *  is not running or when it is locked). */
struct spa_loop_control_hooks {
#define SPA_VERSION_LOOP_CONTROL_HOOKS	0
	uint32_t version;
	/** Executed right before waiting for events. It is typically used to
	 * release locks or integrate other fds into the loop. */
	void (*before) (void *data);
	/** Executed right after waiting for events. It is typically used to
	 * reacquire locks or integrate other fds into the loop. */
	void (*after) (void *data);
};

SPA_API_LOOP void spa_loop_control_hook_before(struct spa_hook_list *l)
{
	struct spa_hook *h;
	spa_list_for_each_reverse(h, &l->list, link)
		spa_callbacks_call_fast(&h->cb, struct spa_loop_control_hooks, before, 0);
}

SPA_API_LOOP void spa_loop_control_hook_after(struct spa_hook_list *l)
{
	struct spa_hook *h;
	spa_list_for_each(h, &l->list, link)
		spa_callbacks_call_fast(&h->cb, struct spa_loop_control_hooks, after, 0);
}

/**
 * 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:
 * \code{.c}
 * spa_loop_control_enter(loop);
 * while (running) {
 *   spa_loop_control_iterate(loop, -1);
 * }
 * spa_loop_control_leave(loop);
 * \endcode
 *
 * 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.
 */
struct spa_loop_control_methods {
	/* the version of this structure. This can be used to expand this
	 * structure in the future */
#define SPA_VERSION_LOOP_CONTROL_METHODS	2
	uint32_t version;

	/** get the loop fd
	 * \param 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.
	 * \return the fd of the loop
	 */
	int (*get_fd) (void *object);

	/** Add a hook
	 * \param object the control to change
	 * \param hooks the hooks to add
	 *
	 * Adds hooks to the loop controlled by \a ctrl.
	 */
	void (*add_hook) (void *object,
			  struct spa_hook *hook,
			  const struct spa_loop_control_hooks *hooks,
			  void *data);

	/** Enter a loop
	 * \param 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. This function will lock the loop.
	 */
	void (*enter) (void *object);
	/** Leave a loop
	 * \param 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().
	 *
	 * This function will unlock the loop.
	 */
	void (*leave) (void *object);

	/** Perform one iteration of the loop.
	 * \param ctrl the control
	 * \param timeout an optional timeout in milliseconds.
	 *	0 for no timeout, -1 for infinite timeout.
	 *
	 * This function will first unlock the loop and then block
	 * up to \a timeout milliseconds, lock the loop again and then
	 * dispatch the fds with activity.
	 *
	 * The number of dispatched fds is returned.
	 */
	int (*iterate) (void *object, int timeout);

	/** Check context of the loop
	 * \param 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.
	 */
	int (*check) (void *object);

	/** Lock the loop.
	 * This will ensure the loop is not in the process of dispatching
	 * callbacks. Since version 2:2
	 *
	 * \param[in] object the control
	 * \return 0 on success or a negative return value on error.
	 */
	int (*lock) (void *object);

	/** Unlock the loop.
	 * Unlocks the loop again so that callbacks can be dispatched
	 * again. Since version 2:2
	 *
	 * \param[in] object the control
	 * \return 0 on success or a negative return value on error.
	 */
	int (*unlock) (void *object);

	/** get the absolute time
	 * Get the current time with \ref timeout that can be used in wait.
	 * Since version 2:2
	 *
	 * This function can be called from any thread.
	 */
	int (*get_time) (void *object, struct timespec *abstime, int64_t timeout);

	/** Wait for a signal
	 * Wait until a thread performs signal. Since version 2:2
	 *
	 * This function must be called with the loop lock. Because this is a
	 * blocking call, it should not be performed from a realtime thread.
	 *
	 * \param[in] object the control
	 * \param[in] abstime the maximum time to wait for the signal or NULL
	 * \return 0 on success or a negative return value on error.
	 */
	int (*wait) (void *object, const struct timespec *abstime);

	/** Signal waiters
	 * Wake up all threads blocked in wait. Since version 2:2
	 * When wait_for_accept is set, this functions blocks until all
	 * threads performed accept.
	 *
	 * This function must be called with the loop lock and is safe to
	 * call from a realtime thread source dispatch functions when
	 * wait_for_accept is false.
	 *
	 * \param[in] object the control
	 * \param[in] wait_for_accept block for accept
	 * \return 0 on success or a negative return value on error.
	 */
	int (*signal) (void *object, bool wait_for_accept);

	/** Accept signalers
	 * Resume the thread that signaled with wait_for accept.
	 *
	 * This function must be called with the loop lock and is safe to
	 * call from a realtime thread source dispatch functions.
	 *
	 * \param[in] object the control
	 * \return 0 on success or a negative return value on error.
	 */
	int (*accept) (void *object);
};

SPA_API_LOOP int spa_loop_control_get_fd(struct spa_loop_control *object)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_control, &object->iface, get_fd, 0);
}
SPA_API_LOOP void spa_loop_control_add_hook(struct spa_loop_control *object,
		struct spa_hook *hook, const struct spa_loop_control_hooks *hooks,
		void *data)
{
	spa_api_method_v(spa_loop_control, &object->iface, add_hook, 0,
			hook, hooks, data);
}
SPA_API_LOOP void spa_loop_control_enter(struct spa_loop_control *object)
{
	spa_api_method_v(spa_loop_control, &object->iface, enter, 0);
}
SPA_API_LOOP void spa_loop_control_leave(struct spa_loop_control *object)
{
	spa_api_method_v(spa_loop_control, &object->iface, leave, 0);
}
SPA_API_LOOP int spa_loop_control_iterate(struct spa_loop_control *object,
		int timeout)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_control, &object->iface, iterate, 0, timeout);
}
SPA_API_LOOP int spa_loop_control_iterate_fast(struct spa_loop_control *object,
		int timeout)
{
	return spa_api_method_fast_r(int, -ENOTSUP,
			spa_loop_control, &object->iface, iterate, 0, timeout);
}
SPA_API_LOOP int spa_loop_control_check(struct spa_loop_control *object)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_control, &object->iface, check, 1);
}
SPA_API_LOOP int spa_loop_control_lock(struct spa_loop_control *object)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_control, &object->iface, lock, 2);
}
SPA_API_LOOP int spa_loop_control_unlock(struct spa_loop_control *object)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_control, &object->iface, unlock, 2);
}
SPA_API_LOOP int spa_loop_control_get_time(struct spa_loop_control *object,
		struct timespec *abstime, int64_t timeout)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_control, &object->iface, get_time, 2, abstime, timeout);
}
SPA_API_LOOP int spa_loop_control_wait(struct spa_loop_control *object,
		const struct timespec *abstime)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_control, &object->iface, wait, 2, abstime);
}
SPA_API_LOOP int spa_loop_control_signal(struct spa_loop_control *object, bool wait_for_accept)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_control, &object->iface, signal, 2, wait_for_accept);
}
SPA_API_LOOP int spa_loop_control_accept(struct spa_loop_control *object)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_control, &object->iface, accept, 2);
}

typedef void (*spa_source_io_func_t) (void *data, int fd, uint32_t mask);
typedef void (*spa_source_idle_func_t) (void *data);
typedef void (*spa_source_event_func_t) (void *data, uint64_t count);
typedef void (*spa_source_timer_func_t) (void *data, uint64_t expirations);
typedef void (*spa_source_signal_func_t) (void *data, int signal_number);

/**
 * Create sources for an event loop
 */
struct spa_loop_utils_methods {
	/* the version of this structure. This can be used to expand this
	 * structure in the future */
#define SPA_VERSION_LOOP_UTILS_METHODS	0
	uint32_t version;

	struct spa_source *(*add_io) (void *object,
				      int fd,
				      uint32_t mask,
				      bool close,
				      spa_source_io_func_t func, void *data);

	int (*update_io) (void *object, struct spa_source *source, uint32_t mask);

	struct spa_source *(*add_idle) (void *object,
					bool enabled,
					spa_source_idle_func_t func, void *data);
	int (*enable_idle) (void *object, struct spa_source *source, bool enabled);

	struct spa_source *(*add_event) (void *object,
					 spa_source_event_func_t func, void *data);
	int (*signal_event) (void *object, struct spa_source *source);

	struct spa_source *(*add_timer) (void *object,
					 spa_source_timer_func_t func, void *data);
	int (*update_timer) (void *object,
			     struct spa_source *source,
			     struct timespec *value,
			     struct timespec *interval,
			     bool absolute);
	struct spa_source *(*add_signal) (void *object,
					  int signal_number,
					  spa_source_signal_func_t func, void *data);

	/** destroy a source allocated with this interface. This function
	 * should only be called when the loop is not running or from the
	 * context of the running loop */
	void (*destroy_source) (void *object, struct spa_source *source);
};

SPA_API_LOOP struct spa_source *
spa_loop_utils_add_io(struct spa_loop_utils *object, int fd, uint32_t mask,
		bool close, spa_source_io_func_t func, void *data)
{
	return spa_api_method_r(struct spa_source *, NULL,
			spa_loop_utils, &object->iface, add_io, 0, fd, mask, close, func, data);
}
SPA_API_LOOP int spa_loop_utils_update_io(struct spa_loop_utils *object,
		struct spa_source *source, uint32_t mask)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_utils, &object->iface, update_io, 0, source, mask);
}
SPA_API_LOOP struct spa_source *
spa_loop_utils_add_idle(struct spa_loop_utils *object, bool enabled,
		spa_source_idle_func_t func, void *data)
{
	return spa_api_method_r(struct spa_source *, NULL,
			spa_loop_utils, &object->iface, add_idle, 0, enabled, func, data);
}
SPA_API_LOOP int spa_loop_utils_enable_idle(struct spa_loop_utils *object,
		struct spa_source *source, bool enabled)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_utils, &object->iface, enable_idle, 0, source, enabled);
}
SPA_API_LOOP struct spa_source *
spa_loop_utils_add_event(struct spa_loop_utils *object, spa_source_event_func_t func, void *data)
{
	return spa_api_method_r(struct spa_source *, NULL,
			spa_loop_utils, &object->iface, add_event, 0, func, data);
}
SPA_API_LOOP int spa_loop_utils_signal_event(struct spa_loop_utils *object,
		struct spa_source *source)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_utils, &object->iface, signal_event, 0, source);
}
SPA_API_LOOP struct spa_source *
spa_loop_utils_add_timer(struct spa_loop_utils *object, spa_source_timer_func_t func, void *data)
{
	return spa_api_method_r(struct spa_source *, NULL,
			spa_loop_utils, &object->iface, add_timer, 0, func, data);
}
SPA_API_LOOP int spa_loop_utils_update_timer(struct spa_loop_utils *object,
		struct spa_source *source, struct timespec *value,
		struct timespec *interval, bool absolute)
{
	return spa_api_method_r(int, -ENOTSUP,
			spa_loop_utils, &object->iface, update_timer, 0, source,
			value, interval, absolute);
}
SPA_API_LOOP struct spa_source *
spa_loop_utils_add_signal(struct spa_loop_utils *object, int signal_number,
		spa_source_signal_func_t func, void *data)
{
	return spa_api_method_r(struct spa_source *, NULL,
			spa_loop_utils, &object->iface, add_signal, 0,
			signal_number, func, data);
}
SPA_API_LOOP void spa_loop_utils_destroy_source(struct spa_loop_utils *object,
		struct spa_source *source)
{
	spa_api_method_v(spa_loop_utils, &object->iface, destroy_source, 0, source);
}

/**
 * \}
 */

#ifdef __cplusplus
}  /* extern "C" */
#endif

#endif /* SPA_LOOP_H */