factor.c
/*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Landon Curt Noll.
*
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*/
#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1989, 1993\n\
The Regents of the University of California. All rights reserved.\n";
#endif /* not lint */
#ifndef lint
#if 0
static char sccsid[] = "@(#)factor.c 8.4 (Berkeley) 5/4/95";
__RCSID("$NetBSD: factor.c,v 1.13 2002/06/18 23:07:36 simonb Exp $");
#endif
static const char rcsid[] =
"$FreeBSD$";
#endif /* not lint */
/*
* factor - factor a number into primes
*
* By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo
*
* chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\
*
* usage:
* factor [-h] [number] ...
*
* The form of the output is:
*
* number: factor1 factor1 factor2 factor3 factor3 factor3 ...
*
* where factor1 < factor2 < factor3 < ...
*
* If no args are given, the list of numbers are read from stdin.
*/
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "primes.h"
#ifdef HAVE_OPENSSL
#include <openssl/bn.h>
#define PRIME_CHECKS 5
static void pollard_pminus1(BIGNUM *); /* print factors for big numbers */
#else
typedef ubig BIGNUM;
typedef u_long BN_ULONG;
#define BN_CTX int
#define BN_CTX_new() NULL
#define BN_new() ((BIGNUM *)calloc(sizeof(BIGNUM), 1))
#define BN_is_zero(v) (*(v) == 0)
#define BN_is_one(v) (*(v) == 1)
#define BN_mod_word(a, b) (*(a) % (b))
static int BN_dec2bn(BIGNUM **a, const char *str);
static int BN_hex2bn(BIGNUM **a, const char *str);
static BN_ULONG BN_div_word(BIGNUM *, BN_ULONG);
static void BN_print_fp(FILE *, const BIGNUM *);
#endif
static void BN_print_dec_fp(FILE *, const BIGNUM *);
static void pr_fact(BIGNUM *); /* print factors of a value */
static void pr_print(BIGNUM *); /* print a prime */
static void usage(void);
static BN_CTX *ctx; /* just use a global context */
static int hflag;
int
main(int argc, char *argv[])
{
BIGNUM *val;
int ch;
char *p, buf[LINE_MAX]; /* > max number of digits. */
ctx = BN_CTX_new();
val = BN_new();
if (val == NULL)
errx(1, "can't initialise bignum");
while ((ch = getopt(argc, argv, "h")) != -1)
switch (ch) {
case 'h':
hflag++;
break;
case '?':
default:
usage();
}
argc -= optind;
argv += optind;
/* No args supplied, read numbers from stdin. */
if (argc == 0)
for (;;) {
if (fgets(buf, sizeof(buf), stdin) == NULL) {
if (ferror(stdin))
err(1, "stdin");
exit (0);
}
for (p = buf; isblank(*p); ++p);
if (*p == '\n' || *p == '\0')
continue;
if (*p == '-')
errx(1, "negative numbers aren't permitted.");
if (BN_dec2bn(&val, buf) == 0 &&
BN_hex2bn(&val, buf) == 0)
errx(1, "%s: illegal numeric format.", buf);
pr_fact(val);
}
/* Factor the arguments. */
else
for (; *argv != NULL; ++argv) {
if (argv[0][0] == '-')
errx(1, "negative numbers aren't permitted.");
if (BN_dec2bn(&val, argv[0]) == 0 &&
BN_hex2bn(&val, argv[0]) == 0)
errx(1, "%s: illegal numeric format.", argv[0]);
pr_fact(val);
}
exit(0);
}
/*
* pr_fact - print the factors of a number
*
* Print the factors of the number, from the lowest to the highest.
* A factor will be printed multiple times if it divides the value
* multiple times.
*
* Factors are printed with leading tabs.
*/
static void
pr_fact(BIGNUM *val)
{
const ubig *fact; /* The factor found. */
/* Firewall - catch 0 and 1. */
if (BN_is_zero(val)) /* Historical practice; 0 just exits. */
exit(0);
if (BN_is_one(val)) {
printf("1: 1\n");
return;
}
/* Factor value. */
if (hflag) {
fputs("0x", stdout);
BN_print_fp(stdout, val);
} else
BN_print_dec_fp(stdout, val);
putchar(':');
for (fact = &prime[0]; !BN_is_one(val); ++fact) {
/* Look for the smallest factor. */
do {
if (BN_mod_word(val, (BN_ULONG)*fact) == 0)
break;
} while (++fact <= pr_limit);
/* Watch for primes larger than the table. */
if (fact > pr_limit) {
#ifdef HAVE_OPENSSL
BIGNUM *bnfact;
bnfact = BN_new();
BN_set_word(bnfact, *(fact - 1));
BN_sqr(bnfact, bnfact, ctx);
if (BN_cmp(bnfact, val) > 0)
pr_print(val);
else
pollard_pminus1(val);
#else
pr_print(val);
#endif
break;
}
/* Divide factor out until none are left. */
do {
printf(hflag ? " 0x%lx" : " %lu", *fact);
BN_div_word(val, (BN_ULONG)*fact);
} while (BN_mod_word(val, (BN_ULONG)*fact) == 0);
/* Let the user know we're doing something. */
fflush(stdout);
}
putchar('\n');
}
static void
pr_print(BIGNUM *val)
{
if (hflag) {
fputs(" 0x", stdout);
BN_print_fp(stdout, val);
} else {
putchar(' ');
BN_print_dec_fp(stdout, val);
}
}
static void
usage(void)
{
fprintf(stderr, "usage: factor [-h] [value ...]\n");
exit(1);
}
#ifdef HAVE_OPENSSL
/* pollard rho, algorithm from Jim Gillogly, May 2000 */
static void
pollard_pminus1(BIGNUM *val)
{
BIGNUM *base, *num, *i, *x;
base = BN_new();
num = BN_new();
i = BN_new();
x = BN_new();
BN_set_word(i, 2);
BN_set_word(base, 2);
for (;;) {
BN_mod_exp(base, base, i, val, ctx);
BN_copy(x, base);
BN_sub_word(x, 1);
BN_gcd(x, x, val, ctx);
if (!BN_is_one(x)) {
if (BN_is_prime(x, PRIME_CHECKS, NULL, NULL,
NULL) == 1)
pr_print(x);
else
pollard_pminus1(x);
fflush(stdout);
BN_div(num, NULL, val, x, ctx);
if (BN_is_one(num))
return;
if (BN_is_prime(num, PRIME_CHECKS, NULL, NULL,
NULL) == 1) {
pr_print(num);
fflush(stdout);
return;
}
BN_copy(val, num);
}
BN_add_word(i, 1);
}
}
/*
* Sigh.. No _decimal_ output to file functions in BN.
*/
static void
BN_print_dec_fp(FILE *fp, const BIGNUM *num)
{
char *buf;
buf = BN_bn2dec(num);
if (buf == NULL)
return; /* XXX do anything here? */
fprintf(fp, buf);
free(buf);
}
#else
static void
BN_print_fp(FILE *fp, const BIGNUM *num)
{
fprintf(fp, "%lx", (unsigned long)*num);
}
static void
BN_print_dec_fp(FILE *fp, const BIGNUM *num)
{
fprintf(fp, "%lu", (unsigned long)*num);
}
static int
BN_dec2bn(BIGNUM **a, const char *str)
{
char *p;
errno = 0;
**a = strtoul(str, &p, 10);
return (errno == 0 && (*p == '\n' || *p == '\0'));
}
static int
BN_hex2bn(BIGNUM **a, const char *str)
{
char *p;
errno = 0;
**a = strtoul(str, &p, 16);
return (errno == 0 && (*p == '\n' || *p == '\0'));
}
static BN_ULONG
BN_div_word(BIGNUM *a, BN_ULONG b)
{
BN_ULONG mod;
mod = *a % b;
*a /= b;
return mod;
}
#endif
