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+/*
+ * 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 audio_output;
+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)(struct audio_output *ao,
+ const struct audio_format *audio_format,
+ const struct config_param *param);
+
+ /**
+ * Free resources allocated by this device.
+ */
+ void (*finish)(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);
+
+ /**
+ * Play a chunk of audio data.
+ */
+ bool (*play)(void *data, const char *playChunk, size_t size);
+
+ /**
+ * 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);
+
+ /**
+ * Try to cancel data which may still be in the device's
+ * buffers.
+ */
+ void (*cancel)(void *data);
+
+ /**
+ * Close the device.
+ */
+ void (*close)(void *data);
+
+ /**
+ * Control the device. Usualy used for implementing
+ * set and get mixer levels
+ */
+ bool (*control)(void *data, int cmd, void *arg);
+
+ /**
+ * Display metadata for the next chunk. Optional method,
+ * because not all devices can display metadata.
+ */
+ void (*send_tag)(void *data, const struct tag *tag);
+};
+
+#endif