2 * Copyright (c) 1989, 1993
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5 * This code is derived from software contributed to Berkeley by
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32 * @(#) Copyright (c) 1989, 1993 The Regents of the University of California. All rights reserved.
33 * @(#)factor.c 8.4 (Berkeley) 5/4/95
34 * $NetBSD: factor.c,v 1.13 2002/06/18 23:07:36 simonb Exp $
35 * $FreeBSD: src/games/factor/factor.c,v 1.9.2.2 2002/10/23 14:59:14 fanf Exp $
36 * $DragonFly: src/games/factor/factor.c,v 1.2 2003/06/17 04:25:23 dillon Exp $
40 * factor - factor a number into primes
42 * By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo
44 * chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\
47 * factor [-h] [number] ...
49 * The form of the output is:
51 * number: factor1 factor1 factor2 factor3 factor3 factor3 ...
53 * where factor1 < factor2 < factor3 < ...
55 * If no args are given, the list of numbers are read from stdin.
69 #include <openssl/bn.h>
70 #define PRIME_CHECKS 5
71 static void pollard_pminus1(BIGNUM *); /* print factors for big numbers */
74 typedef u_long BN_ULONG;
77 #define BN_CTX_new() NULL
78 #define BN_new() ((BIGNUM *)calloc(sizeof(BIGNUM), 1))
79 #define BN_is_zero(v) (*(v) == 0)
80 #define BN_is_one(v) (*(v) == 1)
81 #define BN_mod_word(a, b) (*(a) % (b))
83 static int BN_dec2bn(BIGNUM **a, const char *str);
84 static int BN_hex2bn(BIGNUM **a, const char *str);
85 static BN_ULONG BN_div_word(BIGNUM *, BN_ULONG);
86 static void BN_print_fp(FILE *, const BIGNUM *);
89 static void BN_print_dec_fp(FILE *, const BIGNUM *);
91 static void pr_fact(BIGNUM *); /* print factors of a value */
92 static void pr_print(BIGNUM *); /* print a prime */
93 static void usage(void);
95 static BN_CTX *ctx; /* just use a global context */
99 main(int argc, char *argv[])
103 char *p, buf[LINE_MAX]; /* > max number of digits. */
108 errx(1, "can't initialise bignum");
110 while ((ch = getopt(argc, argv, "h")) != -1)
122 /* No args supplied, read numbers from stdin. */
125 if (fgets(buf, sizeof(buf), stdin) == NULL) {
130 for (p = buf; isblank(*p); ++p);
131 if (*p == '\n' || *p == '\0')
134 errx(1, "negative numbers aren't permitted.");
135 if (BN_dec2bn(&val, buf) == 0 &&
136 BN_hex2bn(&val, buf) == 0)
137 errx(1, "%s: illegal numeric format.", buf);
140 /* Factor the arguments. */
142 for (; *argv != NULL; ++argv) {
143 if (argv[0][0] == '-')
144 errx(1, "negative numbers aren't permitted.");
145 if (BN_dec2bn(&val, argv[0]) == 0 &&
146 BN_hex2bn(&val, argv[0]) == 0)
147 errx(1, "%s: illegal numeric format.", argv[0]);
154 * pr_fact - print the factors of a number
156 * Print the factors of the number, from the lowest to the highest.
157 * A factor will be printed multiple times if it divides the value
160 * Factors are printed with leading tabs.
165 const ubig *fact; /* The factor found. */
167 /* Firewall - catch 0 and 1. */
168 if (BN_is_zero(val)) /* Historical practice; 0 just exits. */
170 if (BN_is_one(val)) {
179 BN_print_fp(stdout, val);
181 BN_print_dec_fp(stdout, val);
183 for (fact = &prime[0]; !BN_is_one(val); ++fact) {
184 /* Look for the smallest factor. */
186 if (BN_mod_word(val, (BN_ULONG)*fact) == 0)
188 } while (++fact <= pr_limit);
190 /* Watch for primes larger than the table. */
191 if (fact > pr_limit) {
196 BN_set_word(bnfact, *(fact - 1));
197 BN_sqr(bnfact, bnfact, ctx);
198 if (BN_cmp(bnfact, val) > 0)
201 pollard_pminus1(val);
208 /* Divide factor out until none are left. */
210 printf(hflag ? " 0x%lx" : " %lu", *fact);
211 BN_div_word(val, (BN_ULONG)*fact);
212 } while (BN_mod_word(val, (BN_ULONG)*fact) == 0);
214 /* Let the user know we're doing something. */
221 pr_print(BIGNUM *val)
224 fputs(" 0x", stdout);
225 BN_print_fp(stdout, val);
228 BN_print_dec_fp(stdout, val);
235 fprintf(stderr, "usage: factor [-h] [value ...]\n");
241 /* pollard p-1, algorithm from Jim Gillogly, May 2000 */
243 pollard_pminus1(BIGNUM *val)
245 BIGNUM *base, *num, *i, *x;
253 BN_set_word(base, 2);
256 BN_mod_exp(base, base, i, val, ctx);
260 BN_gcd(x, x, val, ctx);
263 if (BN_is_prime(x, PRIME_CHECKS, NULL, NULL,
270 BN_div(num, NULL, val, x, ctx);
273 if (BN_is_prime(num, PRIME_CHECKS, NULL, NULL,
286 * Sigh.. No _decimal_ output to file functions in BN.
289 BN_print_dec_fp(FILE *fp, const BIGNUM *num)
293 buf = BN_bn2dec(num);
295 return; /* XXX do anything here? */
303 BN_print_fp(FILE *fp, const BIGNUM *num)
305 fprintf(fp, "%lx", (unsigned long)*num);
309 BN_print_dec_fp(FILE *fp, const BIGNUM *num)
311 fprintf(fp, "%lu", (unsigned long)*num);
315 BN_dec2bn(BIGNUM **a, const char *str)
320 **a = strtoul(str, &p, 10);
321 return (errno == 0 && (*p == '\n' || *p == '\0'));
325 BN_hex2bn(BIGNUM **a, const char *str)
330 **a = strtoul(str, &p, 16);
331 return (errno == 0 && (*p == '\n' || *p == '\0'));
335 BN_div_word(BIGNUM *a, BN_ULONG b)