factor.c revision 1.9
1/* $OpenBSD: factor.c,v 1.9 2001/08/19 17:12:40 pjanzen Exp $ */ 2/* $NetBSD: factor.c,v 1.5 1995/03/23 08:28:07 cgd Exp $ */ 3 4/* 5 * Copyright (c) 1989, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * This code is derived from software contributed to Berkeley by 9 * Landon Curt Noll. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the University of 22 * California, Berkeley and its contributors. 23 * 4. Neither the name of the University nor the names of its contributors 24 * may be used to endorse or promote products derived from this software 25 * without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 30 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 37 * SUCH DAMAGE. 38 */ 39 40#ifndef lint 41static char copyright[] = 42"@(#) Copyright (c) 1989, 1993\n\ 43 The Regents of the University of California. All rights reserved.\n"; 44#endif /* not lint */ 45 46#ifndef lint 47#if 0 48static char sccsid[] = "@(#)factor.c 8.4 (Berkeley) 5/4/95"; 49#else 50static char rcsid[] = "$OpenBSD: factor.c,v 1.9 2001/08/19 17:12:40 pjanzen Exp $"; 51#endif 52#endif /* not lint */ 53 54/* 55 * factor - factor a number into primes 56 * 57 * By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo 58 * 59 * chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\ 60 * 61 * usage: 62 * factor [number] ... 63 * 64 * The form of the output is: 65 * 66 * number: factor1 factor1 factor2 factor3 factor3 factor3 ... 67 * 68 * where factor1 < factor2 < factor3 < ... 69 * 70 * If no args are given, the list of numbers are read from stdin. 71 */ 72 73#include <sys/types.h> 74#include <err.h> 75#include <ctype.h> 76#include <errno.h> 77#include <limits.h> 78#include <stdio.h> 79#include <stdlib.h> 80#include <unistd.h> 81 82#include "primes.h" 83 84/* 85 * prime[i] is the (i+1)th prime. 86 * 87 * We are able to sieve 2^32-1 because this byte table yields all primes 88 * up to 65537 and 65537^2 > 2^32-1. 89 */ 90extern const ubig prime[]; 91extern const ubig *pr_limit; /* largest prime in the prime array */ 92 93void pr_fact __P((ubig)); /* print factors of a value */ 94void usage __P((void)); 95 96int 97main(argc, argv) 98 int argc; 99 char *argv[]; 100{ 101 ubig val; 102 int ch; 103 char *p, buf[100]; /* > max number of digits. */ 104 105 /* revoke privs */ 106 setegid(getgid()); 107 setgid(getgid()); 108 109 while ((ch = getopt(argc, argv, "")) != -1) 110 switch (ch) { 111 case '?': 112 default: 113 usage(); 114 } 115 argc -= optind; 116 argv += optind; 117 118 /* No args supplied, read numbers from stdin. */ 119 if (argc == 0) 120 for (;;) { 121 if (fgets(buf, sizeof(buf), stdin) == NULL) { 122 if (ferror(stdin)) 123 err(1, "stdin"); 124 exit (0); 125 } 126 if (*(p = buf + strlen(buf) - 1) == '\n') 127 *p = '\0'; 128 for (p = buf; isblank(*p); ++p); 129 if (*p == '\0') 130 continue; 131 if (*p == '-') 132 errx(1, "negative numbers aren't permitted."); 133 errno = 0; 134 val = strtoul(buf, &p, 10); 135 if (errno) 136 err(1, "%s", buf); 137 for (; isblank(*p); ++p); 138 if (*p != '\0') 139 errx(1, "%s: illegal numeric format.", buf); 140 pr_fact(val); 141 } 142 /* Factor the arguments. */ 143 else 144 for (; *argv != NULL; ++argv) { 145 if (argv[0][0] == '-') 146 errx(1, "negative numbers aren't permitted."); 147 errno = 0; 148 val = strtoul(argv[0], &p, 10); 149 if (errno) 150 err(1, "%s", argv[0]); 151 if (*p != '\0') 152 errx(1, "%s: illegal numeric format.", argv[0]); 153 pr_fact(val); 154 } 155 exit(0); 156} 157 158/* 159 * pr_fact - print the factors of a number 160 * 161 * If the number is 0 or 1, then print the number and return. 162 * If the number is < 0, print -1, negate the number and continue 163 * processing. 164 * 165 * Print the factors of the number, from the lowest to the highest. 166 * A factor will be printed numtiple times if it divides the value 167 * multiple times. 168 * 169 * Factors are printed with leading tabs. 170 */ 171void 172pr_fact(val) 173 ubig val; /* Factor this value. */ 174{ 175 const ubig *fact; /* The factor found. */ 176 177 /* Firewall - catch 0 and 1. */ 178 if (val == 0) /* Historical practice; 0 just exits. */ 179 exit(0); 180 if (val == 1) { 181 (void)printf("1: 1\n"); 182 return; 183 } 184 185 /* Factor value. */ 186 (void)printf("%lu:", (unsigned long) val); 187 for (fact = &prime[0]; val > 1; ++fact) { 188 /* Look for the smallest factor. */ 189 do { 190 if (val % (long)*fact == 0) 191 break; 192 } while (++fact <= pr_limit); 193 194 /* Watch for primes larger than the table. */ 195 if (fact > pr_limit) { 196 (void)printf(" %lu", (unsigned long) val); 197 break; 198 } 199 200 /* Divide factor out until none are left. */ 201 do { 202 (void)printf(" %lu", (unsigned long) *fact); 203 val /= (long)*fact; 204 } while ((val % (long)*fact) == 0); 205 206 /* Let the user know we're doing something. */ 207 (void)fflush(stdout); 208 } 209 (void)putchar('\n'); 210} 211 212void 213usage() 214{ 215 (void)fprintf(stderr, "usage: factor [value ...]\n"); 216 exit (0); 217} 218