bizhang_-obav/src/lib/mixer/SimpleMixer.hpp

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#pragma once

/** mixer input */
struct mixer_control_s {
	uint8_t			control_group;	/**< group from which the input reads */
	uint8_t			control_index;	/**< index within the control group */
	struct mixer_scaler_s 	scaler;		/**< scaling applied to the input before use */
};

#define MIXER_SIMPLE_SIZE(_icount)	(sizeof(struct mixer_simple_s) + (_icount) * sizeof(struct mixer_control_s))

/** simple mixer */
struct mixer_simple_s {
	uint8_t			control_count;	/**< number of inputs */
	struct mixer_scaler_s	output_scaler;	/**< scaling for the output */
	struct mixer_control_s	controls[0];	/**< actual size of the array is set by control_count */
};

/**
 * Simple summing mixer.
 *
 * Collects zero or more inputs and mixes them to a single output.
 */
class SimpleMixer : public Mixer
{
public:
	/**
	 * Constructor
	 *
	 * @param mixinfo		Mixer configuration.  The pointer passed
	 *				becomes the property of the mixer and
	 *				will be freed when the mixer is deleted.
	 */
	SimpleMixer(ControlCallback control_cb, uintptr_t cb_handle, mixer_simple_s *mixinfo);
	virtual ~SimpleMixer();

	// no copy, assignment, move, move assignment
	SimpleMixer(const SimpleMixer &) = delete;
	SimpleMixer &operator=(const SimpleMixer &) = delete;
	SimpleMixer(SimpleMixer &&) = delete;
	SimpleMixer &operator=(SimpleMixer &&) = delete;

	/**
	 * Factory method with full external configuration.
	 *
	 * Given a pointer to a buffer containing a text description of the mixer,
	 * returns a pointer to a new instance of the mixer.
	 *
	 * @param control_cb		The callback to invoke when fetching a
	 *				control value.
	 * @param cb_handle		Handle passed to the control callback.
	 * @param buf			Buffer containing a text description of
	 *				the mixer.
	 * @param buflen		Length of the buffer in bytes, adjusted
	 *				to reflect the bytes consumed.
	 * @return			A new SimpleMixer instance, or nullptr
	 *				if the text format is bad.
	 */
	static SimpleMixer		*from_text(Mixer::ControlCallback control_cb, uintptr_t cb_handle, const char *buf,
			unsigned &buflen);

	unsigned			mix(float *outputs, unsigned space) override;

	void				groups_required(uint32_t &groups) override;

	/**
	 * Check that the mixer configuration as loaded is sensible.
	 *
	 * Note that this function will call control_cb, but only cares about
	 * error returns, not the input value.
	 *
	 * @return			Zero if the mixer makes sense, nonzero otherwise.
	 */
	int				check();

	unsigned			set_trim(float trim) override;
	unsigned			get_trim(float *trim) override;

private:

	/**
	 * Perform simpler linear scaling.
	 *
	 * @param scaler		The scaler configuration.
	 * @param input			The value to be scaled.
	 * @return			The scaled value.
	 */
	static float			scale(const mixer_scaler_s &scaler, float input);

	/**
	 * Validate a scaler
	 *
	 * @param scaler		The scaler to be validated.
	 * @return			Zero if good, nonzero otherwise.
	 */
	static int			scale_check(struct mixer_scaler_s &scaler);

	static int parse_output_scaler(const char *buf, unsigned &buflen, mixer_scaler_s &scaler);
	static int parse_control_scaler(const char *buf, unsigned &buflen, mixer_scaler_s &scaler, uint8_t &control_group,
					uint8_t &control_index);

	mixer_simple_s			*_pinfo{nullptr};

};