lfsr_test.c

来自「非常好的dns解析软件」· C语言 代码 · 共 96 行

/*
 * Copyright (C) 2004, 2005  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1999-2001  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: lfsr_test.c,v 1.12.18.2 2005/04/29 00:15:46 marka Exp $ */

/*! \file */
#include <config.h>

#include <stdio.h>

#include <isc/lfsr.h>
#include <isc/util.h>

isc_uint32_t state[1024 * 64];

int
main(int argc, char **argv) {
	isc_lfsr_t lfsr1, lfsr2;
	int i;
	isc_uint32_t temp;

	UNUSED(argc);
	UNUSED(argv);

	/*
	 * Verify that returned values are reproducable.
	 */
	isc_lfsr_init(&lfsr1, 0, 32, 0x80000057U, 0, NULL, NULL);
	for (i = 0; i < 32; i++) {
		isc_lfsr_generate(&lfsr1, &state[i], 4);
		printf("lfsr1:  state[%2d] = %08x\n", i, state[i]);
	}
	isc_lfsr_init(&lfsr1, 0, 32, 0x80000057U, 0, NULL, NULL);
	for (i = 0; i < 32; i++) {
		isc_lfsr_generate(&lfsr1, &temp, 4);
		if (state[i] != temp)
			printf("lfsr1:  state[%2d] = %08x, "
			       "but new state is %08x\n",
			       i, state[i], temp);
	}

	/*
	 * Now do the same with skipping.
	 */
	isc_lfsr_init(&lfsr1, 0, 32, 0x80000057U, 0, NULL, NULL);
	for (i = 0; i < 32; i++) {
		isc_lfsr_generate(&lfsr1, &state[i], 4);
		isc_lfsr_skip(&lfsr1, 32);
		printf("lfsr1:  state[%2d] = %08x\n", i, state[i]);
	}
	isc_lfsr_init(&lfsr1, 0, 32, 0x80000057U, 0, NULL, NULL);
	for (i = 0; i < 32; i++) {
		isc_lfsr_generate(&lfsr1, &temp, 4);
		isc_lfsr_skip(&lfsr1, 32);
		if (state[i] != temp)
			printf("lfsr1:  state[%2d] = %08x, "
			       "but new state is %08x\n",
			       i, state[i], temp);
	}

	/*
	 * Try to find the period of the LFSR.
	 *
	 *	x^16 + x^5 + x^3 + x^2 + 1
	 */
	isc_lfsr_init(&lfsr2, 0, 16, 0x00008016U, 0, NULL, NULL);
	for (i = 0; i < 32; i++) {
		isc_lfsr_generate(&lfsr2, &state[i], 4);
		printf("lfsr2:  state[%2d] = %08x\n", i, state[i]);
	}
	isc_lfsr_init(&lfsr2, 0, 16, 0x00008016U, 0, NULL, NULL);
	for (i = 0; i < 32; i++) {
		isc_lfsr_generate(&lfsr2, &temp, 4);
		if (state[i] != temp)
			printf("lfsr2:  state[%2d] = %08x, "
			       "but new state is %08x\n",
			       i, state[i], temp);
	}

	return (0);
}