gr_single_pole_avg.h

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/* -*- c++ -*- */
/*
 * Copyright 2002 Free Software Foundation, Inc.
 * 
 * This file is part of GNU Radio
 * 
 * GNU Radio 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, or (at your option)
 * any later version.
 * 
 * GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */
#ifndef _GR_SINGLE_POLE_AVG_H_
#define _GR_SINGLE_POLE_AVG_H_

#include <stdexcept>

template<class o_type, class i_type, class tap_type> 
class gr_single_pole_avg {
public:
  gr_single_pole_avg (tap_type alpha = 1.0)
  {
    d_prev_input = 0;
    set_taps (alpha);
  }

  o_type filter (const i_type input);

  void filterN (o_type output[], const i_type input[], unsigned long n);

  void set_taps (tap_type alpha)
  { 
    if (alpha < 0 || alpha > 1)
      throw std::out_of_range ("Alpha must be in [0, 1]\n");

    d_alpha = alpha;
    d_one_minus_alpha = 1.0 - alpha;
  }

  void reset ()
  {
    d_prev_input = 0;
  }

  tap_type prev_input () { return d_prev_input; }
    
protected:
  tap_type      d_alpha;
  tap_type      d_one_minus_alpha;
  tap_type      d_prev_input;
};


//
// general case.  We may want to specialize this
//
template<class o_type, class i_type, class tap_type> 
o_type
gr_single_pole_avg<o_type, i_type, tap_type>::filter (const i_type input)
{
  tap_type      output;

  output = d_alpha * input - d_one_minus_alpha * d_prev_input;
  d_prev_input = input;

  return (o_type) output;
}


template<class o_type, class i_type, class tap_type> 
void 
gr_single_pole_avg<o_type, i_type, tap_type>::filterN (o_type output[],
                                                       const i_type input[],
                                                       unsigned long n)
{
  for (unsigned i = 0; i < n; i++)
    output[i] = filter (input[i]);
}


#endif /* _GR_SINGLE_POLE_AVG_H_ */

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