factor.c revision 1.2
1/* $NetBSD: factor.c,v 1.5 1995/03/23 08:28:07 cgd Exp $ */ 2 3/* 4 * Copyright (c) 1989, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Landon Curt Noll. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39#ifndef lint 40static char copyright[] = 41"@(#) Copyright (c) 1989, 1993\n\ 42 The Regents of the University of California. All rights reserved.\n"; 43#endif /* not lint */ 44 45#ifndef lint 46#if 0 47static char sccsid[] = "@(#)factor.c 8.3 (Berkeley) 3/30/94"; 48#else 49static char rcsid[] = "$NetBSD: factor.c,v 1.5 1995/03/23 08:28:07 cgd Exp $"; 50#endif 51#endif /* not lint */ 52 53/* 54 * factor - factor a number into primes 55 * 56 * By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo 57 * 58 * chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\ 59 * 60 * usage: 61 * factor [number] ... 62 * 63 * The form of the output is: 64 * 65 * number: factor1 factor1 factor2 factor3 factor3 factor3 ... 66 * 67 * where factor1 < factor2 < factor3 < ... 68 * 69 * If no args are given, the list of numbers are read from stdin. 70 */ 71 72#include <err.h> 73#include <ctype.h> 74#include <errno.h> 75#include <limits.h> 76#include <stdio.h> 77#include <stdlib.h> 78 79#include "primes.h" 80 81/* 82 * prime[i] is the (i-1)th prime. 83 * 84 * We are able to sieve 2^32-1 because this byte table yields all primes 85 * up to 65537 and 65537^2 > 2^32-1. 86 */ 87extern ubig prime[]; 88extern ubig *pr_limit; /* largest prime in the prime array */ 89 90void pr_fact __P((ubig)); /* print factors of a value */ 91void usage __P((void)); 92 93int 94main(argc, argv) 95 int argc; 96 char *argv[]; 97{ 98 ubig val; 99 int ch; 100 char *p, buf[100]; /* > max number of digits. */ 101 102 setgid(getgid()); 103 104 while ((ch = getopt(argc, argv, "")) != EOF) 105 switch (ch) { 106 case '?': 107 default: 108 usage(); 109 } 110 argc -= optind; 111 argv += optind; 112 113 /* No args supplied, read numbers from stdin. */ 114 if (argc == 0) 115 for (;;) { 116 if (fgets(buf, sizeof(buf), stdin) == NULL) { 117 if (ferror(stdin)) 118 err(1, "stdin"); 119 exit (0); 120 } 121 for (p = buf; isblank(*p); ++p); 122 if (*p == '\n' || *p == '\0') 123 continue; 124 if (*p == '-') 125 errx(1, "negative numbers aren't permitted."); 126 errno = 0; 127 val = strtoul(buf, &p, 10); 128 if (errno) 129 err(1, "%s", buf); 130 if (*p != '\n') 131 errx(1, "%s: illegal numeric format.", buf); 132 pr_fact(val); 133 } 134 /* Factor the arguments. */ 135 else 136 for (; *argv != NULL; ++argv) { 137 if (argv[0][0] == '-') 138 errx(1, "negative numbers aren't permitted."); 139 errno = 0; 140 val = strtoul(argv[0], &p, 10); 141 if (errno) 142 err(1, "%s", argv[0]); 143 if (*p != '\0') 144 errx(1, "%s: illegal numeric format.", argv[0]); 145 pr_fact(val); 146 } 147 exit(0); 148} 149 150/* 151 * pr_fact - print the factors of a number 152 * 153 * If the number is 0 or 1, then print the number and return. 154 * If the number is < 0, print -1, negate the number and continue 155 * processing. 156 * 157 * Print the factors of the number, from the lowest to the highest. 158 * A factor will be printed numtiple times if it divides the value 159 * multiple times. 160 * 161 * Factors are printed with leading tabs. 162 */ 163void 164pr_fact(val) 165 ubig val; /* Factor this value. */ 166{ 167 ubig *fact; /* The factor found. */ 168 169 /* Firewall - catch 0 and 1. */ 170 if (val == 0) /* Historical practice; 0 just exits. */ 171 exit(0); 172 if (val == 1) { 173 (void)printf("1: 1\n"); 174 return; 175 } 176 177 /* Factor value. */ 178 (void)printf("%lu:", val); 179 for (fact = &prime[0]; val > 1; ++fact) { 180 /* Look for the smallest factor. */ 181 do { 182 if (val % (long)*fact == 0) 183 break; 184 } while (++fact <= pr_limit); 185 186 /* Watch for primes larger than the table. */ 187 if (fact > pr_limit) { 188 (void)printf(" %lu", val); 189 break; 190 } 191 192 /* Divide factor out until none are left. */ 193 do { 194 (void)printf(" %lu", *fact); 195 val /= (long)*fact; 196 } while ((val % (long)*fact) == 0); 197 198 /* Let the user know we're doing something. */ 199 (void)fflush(stdout); 200 } 201 (void)putchar('\n'); 202} 203 204void 205usage() 206{ 207 (void)fprintf(stderr, "usage: factor [value ...]\n"); 208 exit (0); 209} 210