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path: root/src/pulse/context.h
 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230  #ifndef foocontexthfoo #define foocontexthfoo /* $Id$ */ /*** This file is part of PulseAudio. 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 #include #include #include #include /** \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