#ifndef foocontexthfoo #define foocontexthfoo /* $Id: context.h 1426 2007-02-13 15:35:19Z ossman $ */ /*** 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 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 USA. ***/ #include <pulse/sample.h> #include <pulse/def.h> #include <pulse/mainloop-api.h> #include <pulse/cdecl.h> #include <pulse/operation.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 functions. This also 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 * thread. * \li \subpage glib-mainloop - A wrapper around GLIB's main loop. Available * for both GLIB 1.2 and GLIB 2.x. * * 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 * 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 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 */ 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); /** Instantiate a new connection context with an abstract mainloop API * and an application name */ pa_context *pa_context_new(pa_mainloop_api *mainloop, const char *name); /** 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); /** 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_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. */ 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. \since 0.4 */ 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. \since 0.4 */ 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. \since 0.5 */ int pa_context_is_local(pa_context *c); /** Set a different application name for context on the server. \since 0.5 */ 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. \since 0.7 */ const char* pa_context_get_server(pa_context *c); /** Return the protocol version of the library. \since 0.8 */ uint32_t pa_context_get_protocol_version(pa_context *c); /** Return the protocol version of the connected server. \since 0.8 */ uint32_t pa_context_get_server_protocol_version(pa_context *c); PA_C_DECL_END #endif