src/pulse/context.h

#ifndef foocontexthfoo
#define foocontexthfoo

/***
  This file is part of PulseAudio.

  Copyright 2004-2006 Lennart Poettering
  Copyright 2006 Pierre Ossman <ossman@cendio.se> 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, see <http://www.gnu.org/licenses/>.
***/

#include <pulse/sample.h>
#include <pulse/def.h>
#include <pulse/mainloop-api.h>
#include <pulse/cdecl.h>
#include <pulse/operation.h>
#include <pulse/proplist.h>
#include <pulse/version.h>

/** \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 Timer events - Events that trigger after a fixed amount 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 amount 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
 *                                  thread.
 * \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 object's 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
 * channel.
 *
 * 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
 * subsections:
 *
 * \li \subpage streams
 * \li \subpage scache
 * \li \subpage introspect
 * \li \subpage subscribe
 */

/** \file
 * Connection contexts for asynchronous communication with a
 * server. A pa_context object wraps a connection to a PulseAudio
 * server using its native protocol.
 *
 * See also \subpage async
 */

PA_C_DECL_BEGIN

/** 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 initial client property
 * list. \since 0.9.11 */
pa_context *pa_context_new_with_proplist(pa_mainloop_api *mainloop, const char *name, const 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 whenever 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(const pa_context *c);

/** Return non-zero if some data is pending to be written to the connection */
int pa_context_is_pending(const pa_context *c);

/** Return the current context status */
pa_context_state_t pa_context_get_state(const 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
 * process. Returns negative on certain errors such as invalid state
 * or parameters. */
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 successfully, 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(const 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(const pa_context *c);

/** Return the protocol version of the library. */
uint32_t pa_context_get_protocol_version(const pa_context *c);

/** Return the protocol version of the connected server.
 * Returns PA_INVALID_INDEX on error. */
uint32_t pa_context_get_server_protocol_version(const pa_context *c);

/** Update the property list of the client, adding new entries. Please
 * note that it is highly recommended to set as many 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, const 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().
 * Returns PA_INVALID_INDEX on error. \since 0.9.11 */
uint32_t pa_context_get_index(const pa_context *s);

/** Create a new timer event source for the specified time (wrapper
 * for mainloop->time_new). \since 0.9.16 */
pa_time_event* pa_context_rttime_new(const pa_context *c, pa_usec_t usec, pa_time_event_cb_t cb, void *userdata);

/** Restart a running or expired timer event source (wrapper for
 * mainloop->time_restart). \since 0.9.16 */
void pa_context_rttime_restart(const pa_context *c, pa_time_event *e, pa_usec_t usec);

/** Return the optimal block size for passing around audio buffers. It
 * is recommended to allocate buffers of the size returned here when
 * writing audio data to playback streams, if the latency constraints
 * permit this. It is not recommended writing larger blocks than this
 * because usually they will then be split up internally into chunks
 * of this size. It is not recommended writing smaller blocks than
 * this (unless required due to latency demands) because this
 * increases CPU usage. If ss is NULL you will be returned the
 * byte-exact tile size. if ss is invalid, (size_t) -1 will be
 * returned. If you pass a valid ss, then the tile size
 * will be rounded down to multiple of the frame size. This is
 * supposed to be used in a construct such as
 * pa_context_get_tile_size(pa_stream_get_context(s),
 * pa_stream_get_sample_spec(ss)); \since 0.9.20 */
size_t pa_context_get_tile_size(const pa_context *c, const pa_sample_spec *ss);

/** Load the authentication cookie from a file. This function is primarily
 * meant for PulseAudio's own tunnel modules, which need to load the cookie
 * from a custom location. Applications don't usually need to care about the
 * cookie at all, but if it happens that you know what the authentication
 * cookie is and your application needs to load it from a non-standard
 * location, feel free to use this function. \since 5.0 */
int pa_context_load_cookie_from_file(pa_context *c, const char *cookie_file_path);

PA_C_DECL_END

#endif