/* Finite Impulse Response (FIR) filter

Copyright (C) 2001-2002 Andrew Rogers

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 */

#include "fir.h"

FIR::FIR(int order, double *coeffs, double *init=NULL)
{
  	h=(double *)malloc(sizeof(double)*(order+1));	//There are order+1 number of coeffs
        delay=(double *)malloc(sizeof(double)*order);
        n=order;
        for(int i=0; i<=n; i++) h[i]=coeffs[i];
        if(init!=NULL) for(int i=0; i<n; i++) delay[i]=init[i];
}

double FIR::sample(double x)
{
	double y=x*h[0];
        for(int i=1; i<=n; i++) y+=h[i]*delay[i-1];
        for(int i=n-1; i>=1; i--) delay[i]=delay[i-1];
        delay[0]=x;
        return y;
}

FIR::~FIR()
{
	free(h); free(delay);
}