This file is part of PulseAudio.
Copyright 2004-2006 Lennart Poettering
Copyright 2006 Pierre Ossman <email@example.com> for Cendio AB
PulseAudio is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation; either version 2.1 of the License,
or (at your option) any later version.
PulseAudio is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with PulseAudio; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
/** \page async Asynchronous API
* \section overv_sec Overview
* The asynchronous API is the native interface to the PulseAudio library.
* It allows full access to all available functionality. This however means that
* it is rather complex and can take some time to fully master.
* \section mainloop_sec Main Loop Abstraction
* The API is based around an asynchronous event loop, or main loop,
* abstraction. This abstraction contains three basic elements:
* \li Deferred events - Events that will trigger as soon as possible. Note
* that some implementations may block all other events
* when a deferred event is active.
* \li I/O events - Events that trigger on file descriptor activities.
* \li Times events - Events that trigger after a fixed ammount of time.
* The abstraction is represented as a number of function pointers in the
* pa_mainloop_api structure.
* To actually be able to use these functions, an implementation needs to
* be coupled to the abstraction. There are three of these shipped with
* PulseAudio, but any other can be used with a minimal ammount of work,
* provided it supports the three basic events listed above.
* The implementations shipped with PulseAudio are:
* \li \subpage mainloop - A minimal but fast implementation based on poll().
* \li \subpage threaded_mainloop - A special version of the previous
* implementation where all of PulseAudio's
* internal handling runs in a separate
* \li \subpage glib-mainloop - A wrapper around GLib's main loop.
* UNIX signals may be hooked to a main loop using the functions from
* \ref mainloop-signal.h. These rely only on the main loop abstraction
* and can therefore be used with any of the implementations.
* \section refcnt_sec Reference Counting
* Almost all objects in PulseAudio are reference counted. What that means
* is that you rarely malloc() or free() any objects. Instead you increase
* and decrease their reference counts. Whenever an object's reference
* count reaches zero, that object gets destroy and any resources it uses
* get freed.
* The benefit of this design is that an application need not worry about
* whether or not it needs to keep an object around in case the library is
* using it internally. If it is, then it has made sure it has its own
* reference to it.
* Whenever the library creates an object, it will have an initial
* reference count of one. Most of the time, this single reference will be
* sufficient for the application, so all required reference count
* interaction will be a single call to the objects unref function.
* \section context_sec Context
* A context is the basic object for a connection to a PulseAudio server.
* It multiplexes commands, data streams and events through a single
* There is no need for more than one context per application, unless
* connections to multiple servers are needed.
* \subsection ops_subsec Operations
* All operations on the context are performed asynchronously. I.e. the
* client will not wait for the server to complete the request. To keep
* track of all these in-flight operations, the application is given a
* pa_operation object for each asynchronous operation.
* There are only two actions (besides reference counting) that can be
* performed on a pa_operation: querying its state with
* pa_operation_get_state() and aborting it with pa_operation_cancel().
* A pa_operation object is reference counted, so an application must
* make sure to unreference it, even if it has no intention of using it.
* \subsection conn_subsec Connecting
* A context must be connected to a server before any operation can be
* issued. Calling pa_context_connect() will initiate the connection
* procedure. Unlike most asynchronous operations, connecting does not
* result in a pa_operation object. Instead, the application should
* register a callback using pa_context_set_state_callback().
* \subsection disc_subsec Disconnecting
* When the sound support is no longer needed, the connection needs to be
* closed using pa_context_disconnect(). This is an immediate function that
* works synchronously.
* Since the context object has references to other objects it must be
* disconnected after use or there is a high risk of memory leaks. If the
* connection has terminated by itself, then there is no need to explicitly
* disconnect the context using pa_context_disconnect().
* \section Functions
* The sound server's functionality can be divided into a number of
* \li \subpage streams
* \li \subpage scache
* \li \subpage introspect
* \li \subpage subscribe
* Connection contexts for asynchrononous communication with a
* server. A pa_context object wraps a connection to a PulseAudio
* server using its native protocol. */
/** \example pacat.c
* A playback and recording tool using the asynchronous API */
/** \example paplay.c
* A sound file playback tool using the asynchronous API, based on libsndfile */
/** An opaque connection context to a daemon */
typedef struct pa_context pa_context;
/** Generic notification callback prototype */
typedef void (*pa_context_notify_cb_t)(pa_context *c, void *userdata);
/** A generic callback for operation completion */
typedef void (*pa_context_success_cb_t) (pa_context *c, int success, void *userdata);
/** A callback for asynchronous meta/policy event messages. The set
* of defined events can be extended at any time. Also, server modules
* may introduce additional message types so make sure that your
* callback function ignores messages it doesn't know. \since
* 0.9.15 */
typedef void (*pa_context_event_cb_t)(pa_context *c, const char *name, pa_proplist *p, void *userdata);
/** Instantiate a new connection context with an abstract mainloop API
* and an application name. It is recommended to use pa_context_new_with_proplist()
* instead and specify some initial properties.*/
pa_context *pa_context_new(pa_mainloop_api *mainloop, const char *name);
/** Instantiate a new connection context with an abstract mainloop API
* and an application name, and specify the the initial client property
* list. \since 0.9.11 */
pa_context *pa_context_new_with_proplist(pa_mainloop_api *mainloop, const char *name, pa_proplist *proplist);
/** Decrease the reference counter of the context by one */
void pa_context_unref(pa_context *c);
/** Increase the reference counter of the context by one */
pa_context* pa_context_ref(pa_context *c);
/** Set a callback function that is called whenever the context status changes */
void pa_context_set_state_callback(pa_context *c, pa_context_notify_cb_t cb, void *userdata);
/** Set a callback function that is called whenver a meta/policy
* control event is received. \since 0.9.15 */
void pa_context_set_event_callback(pa_context *p, pa_context_event_cb_t cb, void *userdata);
/** Return the error number of the last failed operation */
int pa_context_errno(pa_context *c);
/** Return non-zero if some data is pending to be written to the connection */
int pa_context_is_pending(pa_context *c);
/** Return the current context status */
pa_context_state_t pa_context_get_state(pa_context *c);
/** Connect the context to the specified server. If server is NULL,
connect to the default server. This routine may but will not always
return synchronously on error. Use pa_context_set_state_callback() to
be notified when the connection is established. If flags doesn't have
PA_CONTEXT_NOAUTOSPAWN set and no specific server is specified or
accessible a new daemon is spawned. If api is non-NULL, the functions
specified in the structure are used when forking a new child
int pa_context_connect(pa_context *c, const char *server, pa_context_flags_t flags, const pa_spawn_api *api);
/** Terminate the context connection immediately */
void pa_context_disconnect(pa_context *c);
/** Drain the context. If there is nothing to drain, the function returns NULL */
pa_operation* pa_context_drain(pa_context *c, pa_context_notify_cb_t cb, void *userdata);
/** Tell the daemon to exit. The returned operation is unlikely to
* complete succesfully, since the daemon probably died before
* returning a success notification */
pa_operation* pa_context_exit_daemon(pa_context *c, pa_context_success_cb_t cb, void *userdata);
/** Set the name of the default sink. */
pa_operation* pa_context_set_default_sink(pa_context *c, const char *name, pa_context_success_cb_t cb, void *userdata);
/** Set the name of the default source. */
pa_operation* pa_context_set_default_source(pa_context *c, const char *name, pa_context_success_cb_t cb, void *userdata);
/** Returns 1 when the connection is to a local daemon. Returns negative when no connection has been made yet. */
int pa_context_is_local(pa_context *c);
/** Set a different application name for context on the server. */
pa_operation* pa_context_set_name(pa_context *c, const char *name, pa_context_success_cb_t cb, void *userdata);
/** Return the server name this context is connected to. */
const char* pa_context_get_server(pa_context *c);
/** Return the protocol version of the library. */
uint32_t pa_context_get_protocol_version(pa_context *c);
/** Return the protocol version of the connected server. */
uint32_t pa_context_get_server_protocol_version(pa_context *c);
/** Update the property list of the client, adding new entries. Please
* note that it is highly recommended to set as much properties
* initially via pa_context_new_with_proplist() as possible instead a
* posteriori with this function, since that information may then be
* used to route streams of the client to the right device. \since 0.9.11 */
pa_operation *pa_context_proplist_update(pa_context *c, pa_update_mode_t mode, pa_proplist *p, pa_context_success_cb_t cb, void *userdata);
/** Update the property list of the client, remove entries. \since 0.9.11 */
pa_operation *pa_context_proplist_remove(pa_context *c, const char *const keys, pa_context_success_cb_t cb, void *userdata);
/** Return the client index this context is
* identified in the server with. This is useful for usage with the
* introspection functions, such as pa_context_get_client_info(). \since 0.9.11 */
uint32_t pa_context_get_index(pa_context *s);