/* * Copyright (C) 2003-2009 The Music Player Daemon Project * http://www.musicpd.org * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program 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 General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ #ifndef MPD_OUTPUT_PLUGIN_H #define MPD_OUTPUT_PLUGIN_H #include <stdbool.h> #include <stddef.h> struct config_param; struct audio_format; struct tag; /** * A plugin which controls an audio output device. */ struct audio_output_plugin { /** * the plugin's name */ const char *name; /** * Test if this plugin can provide a default output, in case * none has been configured. This method is optional. */ bool (*test_default_device)(void); /** * Configure and initialize the device, but do not open it * yet. * * @param ao an opaque pointer to the audio_output structure * @param audio_format the configured audio format, or NULL if * none is configured * @param param the configuration section, or NULL if there is * no configuration * @return NULL on error, or an opaque pointer to the plugin's * data */ void *(*init)(const struct audio_format *audio_format, const struct config_param *param); /** * Free resources allocated by this device. */ void (*finish)(void *data); /** * Returns the mixer device associated with this audio output. * This does not actually open the mixer device yet. * * @return the mixer object, or NULL if there is no mixer * attached to this audio output */ struct mixer *(*get_mixer)(void *data); /** * Really open the device. * @param audio_format the audio format in which data is going * to be delivered; may be modified by the plugin */ bool (*open)(void *data, struct audio_format *audio_format); /** * Close the device. */ void (*close)(void *data); /** * Display metadata for the next chunk. Optional method, * because not all devices can display metadata. */ void (*send_tag)(void *data, const struct tag *tag); /** * Play a chunk of audio data. * * @return the number of bytes played, or 0 on error */ size_t (*play)(void *data, const void *chunk, size_t size); /** * Try to cancel data which may still be in the device's * buffers. */ void (*cancel)(void *data); /** * Pause the device. If supported, it may perform a special * action, which keeps the device open, but does not play * anything. Output plugins like "shout" might want to play * silence during pause, so their clients won't be * disconnected. Plugins which do not support pausing will * simply be closed, and have to be reopened when unpaused. * * @return false on error (output will be closed then), true * for continue to pause */ bool (*pause)(void *data); }; static inline bool ao_plugin_test_default_device(const struct audio_output_plugin *plugin) { return plugin->test_default_device != NULL ? plugin->test_default_device() : false; } static inline void * ao_plugin_init(const struct audio_output_plugin *plugin, const struct audio_format *audio_format, const struct config_param *param) { return plugin->init(audio_format, param); } static inline void ao_plugin_finish(const struct audio_output_plugin *plugin, void *data) { plugin->finish(data); } static inline struct mixer * ao_plugin_get_mixer(const struct audio_output_plugin *plugin, void *data) { return plugin->get_mixer != NULL ? plugin->get_mixer(data) : NULL; } static inline bool ao_plugin_open(const struct audio_output_plugin *plugin, void *data, struct audio_format *audio_format) { return plugin->open(data, audio_format); } static inline void ao_plugin_close(const struct audio_output_plugin *plugin, void *data) { plugin->close(data); } static inline void ao_plugin_send_tag(const struct audio_output_plugin *plugin, void *data, const struct tag *tag) { if (plugin->send_tag != NULL) plugin->send_tag(data, tag); } static inline size_t ao_plugin_play(const struct audio_output_plugin *plugin, void *data, const void *chunk, size_t size) { return plugin->play(data, chunk, size); } static inline void ao_plugin_cancel(const struct audio_output_plugin *plugin, void *data) { if (plugin->cancel != NULL) plugin->cancel(data); } static inline bool ao_plugin_pause(const struct audio_output_plugin *plugin, void *data) { return plugin->pause != NULL ? plugin->pause(data) : false; } #endif