;************************************************************
; Listing 5 - Implementing $invert in VCS
;
; "A Verilog programming-language-interface primer,"
; EDN, September 2, 1999, pg 75.
; http://www.ednmag.com/ednmag/reg/090299/18ms525.htm
;************************************************************

#include "vcsuser.h"

int invert_calltf(), my_checktf();
void move();

int my_checktf() {
    if (tf_nump() != 1) {
       tf_error("Usage: $invert(register_name);\n");
    }
    if (tf_typep(1) != tf_readwrite) {
       tf_error ("Argument must be a register type\n");
    }
}

int invert_calltf() {
char *val_string;  
/* Temporarily holds the value of the reg */

	/* Step 1 of the algorithm */

	val_string = (char *) malloc(tf_sizep(1)+1);
      /* +1 to accommodate the null char at the end */
	strcpy(val_string, tf_strgetp(1, 'b'));

	/* Step 2 of the algorithm */

	move('1', '2', val_string);
	move('0', '1', val_string);
	move('z', 'x', val_string);
	move('2', '0', val_string);

	/* Step 3 of the algorithm */

	io_printf("$invert: %s --> %s at time %d\n",
	tf_strgetp(1, 'b'), val_string, tf_gettime());
	tf_strdelputp(1, tf_sizep(1), 'b', val_string, 0, 0);
}

void move(from, to, in_str)
char from, to, *in_str;
{
	int i=0;
	while(*(in_str+i)) {
		if (*(in_str+i) == from)
			*(in_str+i) = to;
		i++;
	}
}