#include <stdlib.h>

void main_upsem(char *in, char *out)
{
  *out = *in;
}

void read_tape(char *tim_in, char *data_in, char *data_out)
{
  memcpy(data_out, data_in, 1024);
}

void read_cd(char *tim_in, char *data_in, char *data_out)
{
  memcpy(data_out, data_in, 1024);
}

void choose(char *sw_in, char *data_in1, char *data_in2, char *data_out)
{
  if (sw_in[0]) {
    memcpy(data_out, data_in1, 1024);
  } else {
    memcpy(data_out, data_in2, 1024);
  }
}

/* fir.c - FIR filter in direct form */

/* Usage: y = fir(M, h, w, x); */
/* \(h\) = filter, \(w\) = state, \(x\) = input sample */
/* \(M\) = filter order */
double fir(int M, double *h, double *w, double x) 
{                        
       int i;
       double y;                             /* output sample */

       w[0] = x;                             /* read current input sample \(x\) */

       for (y=0, i=0; i<=M; i++)
              y += h[i] * w[i];              /* compute current output sample \(y\) */

       for (i=M; i>=1; i--)                  /* update states for next call */
              w[i] = w[i-1];                 /* done in reverse order */

       return y;
}

double h_filter[3] = {0.1, 0.2, 0.7};
double w_state[3] = {0, 0, 0};
void amplify_audio(char *data_in, char *data_out)
{
  int i;
  double *sig_in, *sig_out;

  /* first amplify */
  for (i=0;i<1024;i++) {
    data_out[i] = data_in[i] << 2;
  }

  /* then filter */
  sig_in = (double *) data_in;
  sig_out = (double *) data_out;

  for (i=0;i<512;i++) {
    sig_out[i] = fir(3, h_filter, w_state, sig_in[i]);
  }  
}