#include <sys/io.h>
#include <stdio.h>
#include <stdlib.h>

const char *days[] = {
	NULL, "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
};

const char *month[] = {
	NULL, "Jan", "Feb", "Mar", "Apr", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
};

static int getbiosbyte(int address);
static void setbiosbyte(int address, int value);
static int unbcd(int bcdbyte);

int main() {
	if (ioperm(0x70, 2, 1) != 0) {
		perror("Cannot set IO permissions");
		return EXIT_FAILURE;
	}

	printf("%s %s. %02d 20%02d %02d:%02d:%02d\n",
		days[getbiosbyte(0x06)],
		month[unbcd(getbiosbyte(0x08))],
		unbcd(getbiosbyte(0x07)),
		unbcd(getbiosbyte(0x09)),
		unbcd(getbiosbyte(0x04)),
		unbcd(getbiosbyte(0x02)),
		unbcd(getbiosbyte(0x00))
	);

	return EXIT_SUCCESS;
}

static int getbiosbyte(int address) {
	outb(address, 0x70);
	return inb(0x71);
}

static void setbiosbyte(int address, int value) {
	outb(address, 0x70);
	outb(value, 0x71);
}

/* convert a BCD byte into an int */
static int unbcd(int bcdbyte) {
	//	return (bcdbyte & 0xf) + 10 * (bcdbyte >> 8 & 0xf);
	return bcdbyte;
}