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/*
* Copyright (C) 2003-2014 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.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef MPD_OUTPUT_PLUGIN_HXX
#define MPD_OUTPUT_PLUGIN_HXX
#include "Compiler.h"
#include <stddef.h>
struct config_param;
struct AudioFormat;
struct Tag;
struct AudioOutput;
struct MixerPlugin;
class Error;
/**
* A plugin which controls an audio output device.
*/
struct AudioOutputPlugin {
/**
* 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 param the configuration section, or nullptr if there is
* no configuration
* @return nullptr on error, or an opaque pointer to the plugin's
* data
*/
AudioOutput *(*init)(const config_param ¶m,
Error &error);
/**
* Free resources allocated by this device.
*/
void (*finish)(AudioOutput *data);
/**
* Enable the device. This may allocate resources, preparing
* for the device to be opened. Enabling a device cannot
* fail: if an error occurs during that, it should be reported
* by the open() method.
*
* @return true on success, false on error
*/
bool (*enable)(AudioOutput *data, Error &error);
/**
* Disables the device. It is closed before this method is
* called.
*/
void (*disable)(AudioOutput *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)(AudioOutput *data, AudioFormat &audio_format,
Error &error);
/**
* Close the device.
*/
void (*close)(AudioOutput *data);
/**
* Returns a positive number if the output thread shall delay
* the next call to play() or pause(). This should be
* implemented instead of doing a sleep inside the plugin,
* because this allows MPD to listen to commands meanwhile.
*
* @return the number of milliseconds to wait
*/
unsigned (*delay)(AudioOutput *data);
/**
* Display metadata for the next chunk. Optional method,
* because not all devices can display metadata.
*/
void (*send_tag)(AudioOutput *data, const Tag &tag);
/**
* Play a chunk of audio data.
*
* @return the number of bytes played, or 0 on error
*/
size_t (*play)(AudioOutput *data,
const void *chunk, size_t size,
Error &error);
/**
* Wait until the device has finished playing.
*/
void (*drain)(AudioOutput *data);
/**
* Try to cancel data which may still be in the device's
* buffers.
*/
void (*cancel)(AudioOutput *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)(AudioOutput *data);
/**
* The mixer plugin associated with this output plugin. This
* may be nullptr if no mixer plugin is implemented. When
* created, this mixer plugin gets the same #config_param as
* this audio output device.
*/
const MixerPlugin *mixer_plugin;
};
static inline bool
ao_plugin_test_default_device(const AudioOutputPlugin *plugin)
{
return plugin->test_default_device != nullptr
? plugin->test_default_device()
: false;
}
gcc_malloc
AudioOutput *
ao_plugin_init(const AudioOutputPlugin *plugin,
const config_param ¶m,
Error &error);
void
ao_plugin_finish(AudioOutput *ao);
bool
ao_plugin_enable(AudioOutput *ao, Error &error);
void
ao_plugin_disable(AudioOutput *ao);
bool
ao_plugin_open(AudioOutput *ao, AudioFormat &audio_format,
Error &error);
void
ao_plugin_close(AudioOutput *ao);
gcc_pure
unsigned
ao_plugin_delay(AudioOutput *ao);
void
ao_plugin_send_tag(AudioOutput *ao, const Tag &tag);
size_t
ao_plugin_play(AudioOutput *ao, const void *chunk, size_t size,
Error &error);
void
ao_plugin_drain(AudioOutput *ao);
void
ao_plugin_cancel(AudioOutput *ao);
bool
ao_plugin_pause(AudioOutput *ao);
#endif
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