ocarina/include/core/driver.h

/**
 * @file
 * Copyright 2014 (c) Anna Schumaker.
 */
#ifndef OCARINA_CORE_DRIVER_H
#define OCARINA_CORE_DRIVER_H

#include <string>

/** Use to convert nanoseconds to seconds */
static const unsigned long O_SECOND = 1000000000;


/**
 * The audio driver class gives us an interface for using multiple
 * audio frameworks for audio playback.
 */
class Driver {
protected:
	void (*on_eos)   (); /**< End-of-stream callback function.   */
	void (*on_error) (); /**< Error handling callback function.  */

public:
	Driver();  /**< Default Driver constructor. */
	virtual ~Driver(); /**< Driver destructor.          */

	/**
	 * Initialize an audio driver.
	 *
	 * @param  argc  Argc passed to the application's main() function.
	 * @param  argv  Argv passed to the applicaiton's main() function.
	 * @param  eos_cb  End-of-stream callback function.
	 * @param  error_cb  Callback function used when the audio library encounters an error.
	 */
	virtual void init(int *argc, char ***argv, void (*eos_cb)(), void (*error_cb)()) = 0;


	/**
	 * Loads an audio file for playback.
	 *
	 * @param  file  Filepath of the track to load.
	 */
	virtual void load(const std::string &file) = 0;

	/**
	 * Called to begin playback on the currently loaded track.
	 *
	 * @return True if playback state was changed successfully, false otherwise.
	 */
	virtual bool play() = 0;

	/**
	 * Called to pause playback on the currently loaded track.
	 *
	 * @return True if playback state was changed successfully, false otherwise.
	 */
	virtual bool pause() = 0;

	/**
	 * Called to check if the audio library is currently playing a track.
	 *
	 * @return True if audio library is playing, false otherwise.
	 */
	virtual bool is_playing() = 0;


	/**
	 * Seek to a specific position in the current track.
	 *
	 * @param  offset  Position from the beginning of the track where we will seek to, in nanoseconds.
	 */
	virtual void seek_to(long offset) = 0;

	/**
	 * Return the current position of the playback.
	 *
	 * @return The current playback position, in nanoseconds.
	 */
	virtual long position() = 0;

	/**
	 * Return the duration of the currently loaded track.
	 *
	 * @return The duration of the current track, in nanoseconds.
	 */
	virtual long duration() = 0;
};


#ifdef CONFIG_TEST
class TestDriver : public Driver
{
public:
	bool playing;
	long cur_pos;
	long cur_duration;
	std::string cur_file;

	TestDriver();
	~TestDriver();
	void init(int *, char ***, void (*)(), void (*)());

	void load(const std::string &);
	bool play();
	bool pause();
	bool is_playing();

	void seek_to(long);
	long position();
	long duration();

	void eos();
	void error();
};
#else /* !CONFIG_TEST */

#include <gst/gst.h>

/**
 * Driver for the GStreamer audio library.
 *
 * The shell command `gst-inspect-1.0 --help-gst` details the command line
 * options that can be passed to Ocarina.
 */
class GSTDriver : public Driver
{
private:
	GstElement *player;
	std::string cur_file;
	bool change_state(GstState state);

public:
	/**
	 * GStreamer audio driver constructor.
	 */
	GSTDriver();

	/**
	 * GStreamer audio driver destructor.
	 */
	~GSTDriver();

	/**
	 * Called to initialize the GStreamer audio driver.
	 * @param  argc  Argc passed to the application's main() function.
	 * @param  argv  Argv passed to the applicaiton's main() function.
	 * @param  eos_cb  End-of-stream callback function.
	 * @param  error_cb  Callback function used when the audio library encounters an error.
	 */
	void init(int *, char ***, void (*)(), void (*)());

	/**
	 * Load a track into the gstreamer pipeline.
	 * @param  filepath  The file to be loaded.
	 */
	void load(const std::string &);

	/**
	 * Begin playback on the GStreamer pipeline.
	 * @return True if the state change was successful.
	 */
	bool play();

	/**
	 * Pause the GStreamer pipeline.
	 * @return True if the state change was successful.
	 */
	bool pause();

	/**
	 * Check if the GStreamer pipeline is playing.
	 * @return True if the pipeline is playing.
	 */
	bool is_playing();


	/**
	 * Seek to a specific position in the pipeline.
	 * @param  offset  Offset from the beginning of the pipeline, in nanoseconds.
	 */
	void seek_to(long);

	/**
	 * Find the current playback position of the pipeline.
	 * @return The current position of the pipeline, in nanoseconds.
	 */
	long position();

	/**
	 * Find the duration of the pipeline.
	 * @return The duration of the pipeline, in nanoseconds.
	 */
	long duration();


	/**
	 * Called to handle messages from the GStreamer bus.
	 * @param  message  The message to be handled.
	 */
	void on_message(GstMessage *);
};
#endif /* CONFIG_TEST */


/**
 * Namespace for audio driver access.
 */
namespace driver
{

	/**
	 * Called to access an audio driver.
	 *
	 * @return The current driver used by the application.
	 */
	Driver *get_driver();

}

#endif /* OCARINA_CORE_DRIVER_H */