Sine.h

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/*
        dsp/Sine.h
        
        Copyright 2003-4 Tim Goetze <tim@quitte.de>
        
        http://quitte.de/dsp/
 
        direct form I recursive sin() generator.
 
*/
/*
        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 or point your web browser to http://www.gnu.org.
*/
 
#ifndef _DSP_SINE_H_
#define _DSP_SINE_H_
 
namespace DSP {
        
class Sine
{
        protected:
                int z;
                double y[2];
                double b;
 
        public:
                Sine()
                        { 
                                b = 0;
                                y[0] = y[1] = 0;
                                z = 0;
                        }
 
                Sine (double f, double fs, double phase)
                        {
                                set_f (f, fs, phase);
                        }
 
                Sine (double omega, double phase = 0.)
                        {
                                set_f (omega, phase);
                        }
 
                inline void set_f (double f, double fs, double phase)
                        {
                                set_f (f * M_PI / fs, phase);
                        }
 
                inline void set_f (double w, double phase)
                        {
                                b = 2 * cos (w);
                                y[0] = sin (phase - w);
                                y[1] = sin (phase - w * 2);
                                z = 0;
                        }
 
                /* advance and return 1 sample */
                inline double get()
                        {
                                double s = b * y[z]; 
                                z ^= 1;
                                s -= y[z];
                                return y[z] = s;
                        }
 
                double get_phase()
                        {
                                double x0 = y[z], x1 = b * y[z] - y[z^1];
                                double phi = asin (x0);
                                
                                /* slope is falling, we're into the 2nd half. */
                                if (x1 < x0)
                                        return M_PI - phi;
 
                                return phi;
                        }
};
 
} /* namespace DSP */
 
#endif /* _DSP_SINE_H_ */