5 This file is part of PulseAudio.
7 Copyright 2004-2006 Lennart Poettering
8 Copyright 2006 Pierre Ossman <ossman@cendio.se> for Cendio AB
10 PulseAudio is free software; you can redistribute it and/or modify
11 it under the terms of the GNU Lesser General Public License as published
12 by the Free Software Foundation; either version 2.1 of the License,
13 or (at your option) any later version.
15 PulseAudio is distributed in the hope that it will be useful, but
16 WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 General Public License for more details.
20 You should have received a copy of the GNU Lesser General Public License
21 along with PulseAudio; if not, write to the Free Software
22 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
26 #include <pulse/sample.h>
27 #include <pulse/def.h>
28 #include <pulse/mainloop-api.h>
29 #include <pulse/cdecl.h>
30 #include <pulse/operation.h>
31 #include <pulse/proplist.h>
32 #include <pulse/version.h>
34 /** \page async Asynchronous API
36 * \section overv_sec Overview
38 * The asynchronous API is the native interface to the PulseAudio library.
39 * It allows full access to all available functionality. This however means that
40 * it is rather complex and can take some time to fully master.
42 * \section mainloop_sec Main Loop Abstraction
44 * The API is based around an asynchronous event loop, or main loop,
45 * abstraction. This abstraction contains three basic elements:
47 * \li Deferred events - Events that will trigger as soon as possible. Note
48 * that some implementations may block all other events
49 * when a deferred event is active.
50 * \li I/O events - Events that trigger on file descriptor activities.
51 * \li Times events - Events that trigger after a fixed amount of time.
53 * The abstraction is represented as a number of function pointers in the
54 * pa_mainloop_api structure.
56 * To actually be able to use these functions, an implementation needs to
57 * be coupled to the abstraction. There are three of these shipped with
58 * PulseAudio, but any other can be used with a minimal amount of work,
59 * provided it supports the three basic events listed above.
61 * The implementations shipped with PulseAudio are:
63 * \li \subpage mainloop - A minimal but fast implementation based on poll().
64 * \li \subpage threaded_mainloop - A special version of the previous
65 * implementation where all of PulseAudio's
66 * internal handling runs in a separate
68 * \li \subpage glib-mainloop - A wrapper around GLib's main loop.
70 * UNIX signals may be hooked to a main loop using the functions from
71 * \ref mainloop-signal.h. These rely only on the main loop abstraction
72 * and can therefore be used with any of the implementations.
74 * \section refcnt_sec Reference Counting
76 * Almost all objects in PulseAudio are reference counted. What that means
77 * is that you rarely malloc() or free() any objects. Instead you increase
78 * and decrease their reference counts. Whenever an object's reference
79 * count reaches zero, that object gets destroy and any resources it uses
82 * The benefit of this design is that an application need not worry about
83 * whether or not it needs to keep an object around in case the library is
84 * using it internally. If it is, then it has made sure it has its own
87 * Whenever the library creates an object, it will have an initial
88 * reference count of one. Most of the time, this single reference will be
89 * sufficient for the application, so all required reference count
90 * interaction will be a single call to the objects unref function.
92 * \section context_sec Context
94 * A context is the basic object for a connection to a PulseAudio server.
95 * It multiplexes commands, data streams and events through a single
98 * There is no need for more than one context per application, unless
99 * connections to multiple servers are needed.
101 * \subsection ops_subsec Operations
103 * All operations on the context are performed asynchronously. I.e. the
104 * client will not wait for the server to complete the request. To keep
105 * track of all these in-flight operations, the application is given a
106 * pa_operation object for each asynchronous operation.
108 * There are only two actions (besides reference counting) that can be
109 * performed on a pa_operation: querying its state with
110 * pa_operation_get_state() and aborting it with pa_operation_cancel().
112 * A pa_operation object is reference counted, so an application must
113 * make sure to unreference it, even if it has no intention of using it.
115 * \subsection conn_subsec Connecting
117 * A context must be connected to a server before any operation can be
118 * issued. Calling pa_context_connect() will initiate the connection
119 * procedure. Unlike most asynchronous operations, connecting does not
120 * result in a pa_operation object. Instead, the application should
121 * register a callback using pa_context_set_state_callback().
123 * \subsection disc_subsec Disconnecting
125 * When the sound support is no longer needed, the connection needs to be
126 * closed using pa_context_disconnect(). This is an immediate function that
127 * works synchronously.
129 * Since the context object has references to other objects it must be
130 * disconnected after use or there is a high risk of memory leaks. If the
131 * connection has terminated by itself, then there is no need to explicitly
132 * disconnect the context using pa_context_disconnect().
136 * The sound server's functionality can be divided into a number of
139 * \li \subpage streams
140 * \li \subpage scache
141 * \li \subpage introspect
142 * \li \subpage subscribe
146 * Connection contexts for asynchronous communication with a
147 * server. A pa_context object wraps a connection to a PulseAudio
148 * server using its native protocol.
150 * See also \subpage async
155 /** An opaque connection context to a daemon */
156 typedef struct pa_context pa_context;
158 /** Generic notification callback prototype */
159 typedef void (*pa_context_notify_cb_t)(pa_context *c, void *userdata);
161 /** A generic callback for operation completion */
162 typedef void (*pa_context_success_cb_t) (pa_context *c, int success, void *userdata);
164 /** A callback for asynchronous meta/policy event messages. The set
165 * of defined events can be extended at any time. Also, server modules
166 * may introduce additional message types so make sure that your
167 * callback function ignores messages it doesn't know. \since
169 typedef void (*pa_context_event_cb_t)(pa_context *c, const char *name, pa_proplist *p, void *userdata);
171 /** Instantiate a new connection context with an abstract mainloop API
172 * and an application name. It is recommended to use pa_context_new_with_proplist()
173 * instead and specify some initial properties.*/
174 pa_context *pa_context_new(pa_mainloop_api *mainloop, const char *name);
176 /** Instantiate a new connection context with an abstract mainloop API
177 * and an application name, and specify the the initial client property
178 * list. \since 0.9.11 */
179 pa_context *pa_context_new_with_proplist(pa_mainloop_api *mainloop, const char *name, pa_proplist *proplist);
181 /** Decrease the reference counter of the context by one */
182 void pa_context_unref(pa_context *c);
184 /** Increase the reference counter of the context by one */
185 pa_context* pa_context_ref(pa_context *c);
187 /** Set a callback function that is called whenever the context status changes */
188 void pa_context_set_state_callback(pa_context *c, pa_context_notify_cb_t cb, void *userdata);
190 /** Set a callback function that is called whenever a meta/policy
191 * control event is received. \since 0.9.15 */
192 void pa_context_set_event_callback(pa_context *p, pa_context_event_cb_t cb, void *userdata);
194 /** Return the error number of the last failed operation */
195 int pa_context_errno(pa_context *c);
197 /** Return non-zero if some data is pending to be written to the connection */
198 int pa_context_is_pending(pa_context *c);
200 /** Return the current context status */
201 pa_context_state_t pa_context_get_state(pa_context *c);
203 /** Connect the context to the specified server. If server is NULL,
204 connect to the default server. This routine may but will not always
205 return synchronously on error. Use pa_context_set_state_callback() to
206 be notified when the connection is established. If flags doesn't have
207 PA_CONTEXT_NOAUTOSPAWN set and no specific server is specified or
208 accessible a new daemon is spawned. If api is non-NULL, the functions
209 specified in the structure are used when forking a new child
211 int pa_context_connect(pa_context *c, const char *server, pa_context_flags_t flags, const pa_spawn_api *api);
213 /** Terminate the context connection immediately */
214 void pa_context_disconnect(pa_context *c);
216 /** Drain the context. If there is nothing to drain, the function returns NULL */
217 pa_operation* pa_context_drain(pa_context *c, pa_context_notify_cb_t cb, void *userdata);
219 /** Tell the daemon to exit. The returned operation is unlikely to
220 * complete successfully, since the daemon probably died before
221 * returning a success notification */
222 pa_operation* pa_context_exit_daemon(pa_context *c, pa_context_success_cb_t cb, void *userdata);
224 /** Set the name of the default sink. */
225 pa_operation* pa_context_set_default_sink(pa_context *c, const char *name, pa_context_success_cb_t cb, void *userdata);
227 /** Set the name of the default source. */
228 pa_operation* pa_context_set_default_source(pa_context *c, const char *name, pa_context_success_cb_t cb, void *userdata);
230 /** Returns 1 when the connection is to a local daemon. Returns negative when no connection has been made yet. */
231 int pa_context_is_local(pa_context *c);
233 /** Set a different application name for context on the server. */
234 pa_operation* pa_context_set_name(pa_context *c, const char *name, pa_context_success_cb_t cb, void *userdata);
236 /** Return the server name this context is connected to. */
237 const char* pa_context_get_server(pa_context *c);
239 /** Return the protocol version of the library. */
240 uint32_t pa_context_get_protocol_version(pa_context *c);
242 /** Return the protocol version of the connected server. */
243 uint32_t pa_context_get_server_protocol_version(pa_context *c);
245 /** Update the property list of the client, adding new entries. Please
246 * note that it is highly recommended to set as much properties
247 * initially via pa_context_new_with_proplist() as possible instead a
248 * posteriori with this function, since that information may then be
249 * used to route streams of the client to the right device. \since 0.9.11 */
250 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);
252 /** Update the property list of the client, remove entries. \since 0.9.11 */
253 pa_operation *pa_context_proplist_remove(pa_context *c, const char *const keys[], pa_context_success_cb_t cb, void *userdata);
255 /** Return the client index this context is
256 * identified in the server with. This is useful for usage with the
257 * introspection functions, such as pa_context_get_client_info(). \since 0.9.11 */
258 uint32_t pa_context_get_index(pa_context *s);
260 /** Create a new timer event source for the specified time (wrapper
261 * for mainloop->time_new). \since 0.9.16 */
262 pa_time_event* pa_context_rttime_new(pa_context *c, pa_usec_t usec, pa_time_event_cb_t cb, void *userdata);
264 /** Restart a running or expired timer event source (wrapper for
265 * mainloop->time_restart). \since 0.9.16 */
266 void pa_context_rttime_restart(pa_context *c, pa_time_event *e, pa_usec_t usec);
268 /** Return the optimal block size for passing around audio buffers. It
269 * is recommended to allocate buffers of the size returned here when
270 * writing audio data to playback streams, if the latency constraints
271 * permit this. It is not recommended writing larger blocks than this
272 * because usually they will then be split up internally into chunks
273 * of this size. It is not recommended writing smaller blocks than
274 * this (unless required due to latency demands) because this
275 * increases CPU usage. If ss is NULL you will be returned the
276 * byte-exact tile size. If you pass a valid ss, then the tile size
277 * will be rounded down to multiple of the frame size. This is
278 * supposed to be used in a construct such as
279 * pa_context_get_tile_size(pa_stream_get_context(s),
280 * pa_stream_get_sample_spec(ss)); \since 0.9.20 */
281 size_t pa_context_get_tile_size(pa_context *c, const pa_sample_spec *ss);