/*-
 * Copyright (c) 2007 Wojciech A. Koszek <wkoszek@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * [id for your version control system, if any]
 */
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/*
 * Zwraca binarną reprezentację liczny typu int.
 */
static char *
pb(int x)
{
	char s[64];
	int i;
	int j;

	memset(s, '0', sizeof(s));

	j = 31;
	i = 1;
	s[j + 1] = '\0';

	while (j >= 0) {
		if (x & i)
			s[j] = '1';
		i *= 2;
		j--;
	}
	return (strdup(s));
}

/*
 * każda bramka tutaj to XOR.
 *
 * IN4 -------+-------------------- out4
 *            +===__
 *               |  \
 *               |  ,'------------- out3
 * IN3 -------+==+-+ 
 *            |
 *            +===__
 *               |  \
 *               |  ,'------------- out2
 * IN2 -------+==+-+
 *            |
 *            +===__
 *               |  \
 *               |  ,'------------- out1
 * IN1 -------+==+-+
 *            |
 *            +===__
 *               |  \
 *               |  ,'------------- out0
 * IN0 -------+==+-+
 * 
 */

/*
 * A bit of bitwise magic.
 */
static int
wk_gray(int n)
{
	int r;
	int idx;
	int k;
	int i1, i2;

	idx = sizeof(n) * 8;
	idx -= 1;		/* should be 31 */

	assert(idx == 31);

	r = (n >> idx);
	r <<= idx;
	while (idx >= 1) {
		i1 = (n >> idx);
		idx -= 1;
		i2 = (n >> idx);
		k = i1 ^ i2;
		r |= k << idx;
	}
	return (r);
}

int
main(int argc __unused, char **argv __unused)
{
	int i;
	int gc;
	char *s;

#define N 64

	printf("i\tgc\tdesc\n");
	for (i = 0; i < N; i++) {
		gc = wk_gray(i);
		s = pb(gc);
		assert(s != NULL && "niemozliwe");
		printf("%d[%x]\t%d[%x]\t%s\n", i, i, gc, gc, s);
		free(s);
	}
	exit(EXIT_SUCCESS);
}