/*
 *	Copyright (C) 2009,2013 by Jonathan Naylor, G4KLX
 *
 *	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; version 2 of the License.
 *
 *	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.
 */

#ifndef	FIRFilter_H
#define	FIRFilter_H

/*
 * Direct-form FIR (Finite Impulse Response) filter operating on float samples.
 *
 * Used by the GMSK modulator and demodulator to implement the Gaussian pulse-
 * shaping filter required by the D-Star GMSK modulation scheme (BT=0.5).
 *
 * process() convolves input samples with the tap coefficients using a circular
 * delay buffer.  reset() clears the delay line without changing the tap set.
 */
class CFIRFilter {
public:
	CFIRFilter(const float* taps, unsigned int length);
	CFIRFilter();
	~CFIRFilter();

	void  setTaps(const float* taps, unsigned int length);

	float process(float val);
	void  process(float* inOut, unsigned int length);
	void  process(const float* in, float* out, unsigned int length);

	void  reset();

private:
	float*       m_taps;
	unsigned int m_length;
	float*       m_buffer;   // Circular delay line for the filter state.
	unsigned int m_bufLen;
	unsigned int m_pointer;
};

#endif