Delay.h

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/*
        dsp/Delay.h
        
        Copyright 2003-4, 2010 Tim Goetze <tim@quitte.de>
        
        http://quitte.de/dsp/
 
        delay lines with fractional (linear or cubic interpolation) lookup 
        and an allpass interpolating tap (which needs more work).
 
        delay line storage is aligned to powers of two for simplified wrapping
        checks (no conditional or modulo, binary and suffices instead).
 
*/
/*
        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_DELAY_H_
#define _DSP_DELAY_H_
 
#include "util.h"
#include "FPTruncateMode.h"
 
namespace DSP {
        
class Delay
{
        public:
                int size;
                sample_t * data;
                int read, write;
 
                Delay()
                        {
                                read = write = 0;
                                data = 0;
                        }
 
                ~Delay()
                        {
                                if (data) free (data);
                        }
 
                void init (int n)
                        {
                                size = next_power_of_2 (n);
                                data = (sample_t *) calloc (sizeof (sample_t), size);
                                size -= 1;
                                write = n;
                        }
 
                void reset()
                        {
                                memset (data, 0, (size + 1) * sizeof (sample_t));
                        }
 
                sample_t & 
                operator [] (int i)
                        {
                                return data [(write - i) & size];
                        }
 
                inline void 
                put (sample_t x)
                        {
                                data [write] = x;
                                write = (write + 1) & size;
                        }
 
                inline sample_t 
                get()
                        {
                                sample_t x = data [read];
                                read = (read + 1) & size;
                                return x;
                        }
 
                inline sample_t
                putget (sample_t x)
                        {
                                put (x);
                                return get();
                        }
 
                /* fractional lookup, linear interpolation */
                inline sample_t 
                get_at (float f)
                        {
                                int n;
                                fistp (f, n); /* read: i = (int) f; relies on FPTruncateMode */
                                f -= n;
                                
                                return (1 - f) * (*this) [n] + f * (*this) [n + 1];
                        }
 
                /* fractional lookup, cubic interpolation */
                inline sample_t
                get_cubic (float f)
                        {
                                int n;
                                fistp (f, n); /* see FPTruncateMode */
                                f -= n;
 
                                sample_t x_1 = (*this) [n - 1];
                                sample_t x0 = (*this) [n];
                                sample_t x1 = (*this) [n + 1];
                                sample_t x2 = (*this) [n + 2];
 
                                /* sample_t (32bit) quicker than double here */
                                sample_t a = 
                                                (3 * (x0 - x1) - x_1 + x2) * .5;
                                sample_t b =
                                                2 * x1 + x_1 - (5 * x0 + x2) * .5;
                                sample_t c = 
                                                (x1 - x_1) * .5;
 
                                return x0 + (((a * f) + b) * f + c) * f;
                        }
};
 
/* allpass variant */
 
class DelayTapA
{
        public:
                sample_t x1, y1;
 
                DelayTapA()
                        {
                                reset();
                        }
 
                void reset()
                        {
                                x1 = y1 = 0;
                        }
 
                sample_t get (Delay & d, float f)
                        {
                                int n;
                                fistp (f, n); /* read: n = (int) f; relies on FPTruncateMode */
                                f -= n;
 
                                sample_t x = d[n];
                                f = (1 - f) / (1 + f);
                                y1 = x1 + f * x - f * y1;
                                x1 = x;
                                return y1;
                        }
};
 
}; /* namespace DSP */
 
#endif /* _DSP_DELAY_H_ */