/* High-security I/O. */
int read_high(void) {
  int n = 0;
  /* Input n from high channel... */
  return n;
}
void write_high(int n){
  /* Output n to high channel...  */
  return;
}

/* Low-security I/O. */
int read_low(void)
{
  int n = 0;
  /* Input n from low channel...  */
  return n;
}
void write_low(int n) {
  /* Output n to low channel...   */
  return;
}

/* Various functions. */
int f1(int y){ int x; x = y; return(x); }
int f2(int y){ int x; x = y; return(x); }
int f3(int y){ int x; x = y; return(x); }
int f4(int y){ int x; x = y; return(x); }
int f5(int y){ int x; x = y; return(x); }
int f6(int y){ int x; x = y; return(x); }

int cache = 0;
void save(int y) { cache = y; }

void main(void)
{
  int hi, lo, *p, **q;
  void (*fptr)(int);
  char s[20];

  p = &hi;
  q = &p;
  fptr = write_low;

  /* 1. No flow from high channel to low channel. */
  hi = read_high();
  lo = read_low();
  write_high(f1(hi));
  write_low(f2(lo));
  write_high(f3(lo));
  write_low(cache);

  /* 2. Flow from high channel to low channel
     via data dependence. */
  hi = read_high();
  lo = read_low();
  lo = f4(lo);
  hi = f5(hi);
  lo = f6(hi);
  write_high(hi);
  write_low(lo);

  /* 3. Flow from high channel to low channel
     via control dependence. */
  hi = read_high();
  lo = 0;
  if (hi){
    write_high(1);
    lo = 1;
    write_high(1);
  }
  write_low(lo);

  /* 4. Flow from high channel to low channel
     via global variable. */
  save(read_high());
  write_low(cache);

  /* 5. Flow from high channel to low channel
     via a pointer */
  hi = read_high();
  write_low(*p);

  /* 6. Flow from high channel to low channel
     via a double pointer */
  hi = read_high();
  write_low(**q);

  /* 7. Flow from high channel to low channel
     via function indirection */
  hi = read_high();
  fptr(hi);

  /* 8. Flow from high channel to low channel
     via pointer casting */
  hi = read_high();
  p = (int *)hi;
  write_low((int)*q);

  /* 9. Flow from high to low through a string
     value.  The dependence is sensitive to 
     standard library models. */
  lo = 0;
  hi = read_high();
  sprintf(s,"%d",hi);
  sscanf(s,"%d",&lo);
  write_low(lo);
}