factor.c revision 42357
1/* 2 * Copyright (c) 1989, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Landon Curt Noll. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37#ifndef lint 38static char copyright[] = 39"@(#) Copyright (c) 1989, 1993\n\ 40 The Regents of the University of California. All rights reserved.\n"; 41#endif /* not lint */ 42 43#ifndef lint 44static char sccsid[] = "@(#)factor.c 8.4 (Berkeley) 5/4/95"; 45#endif /* not lint */ 46 47/* 48 * factor - factor a number into primes 49 * 50 * By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo 51 * 52 * chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\ 53 * 54 * usage: 55 * factor [number] ... 56 * 57 * The form of the output is: 58 * 59 * number: factor1 factor1 factor2 factor3 factor3 factor3 ... 60 * 61 * where factor1 < factor2 < factor3 < ... 62 * 63 * If no args are given, the list of numbers are read from stdin. 64 */ 65 66#include <err.h> 67#include <ctype.h> 68#include <errno.h> 69#include <limits.h> 70#include <stdio.h> 71#include <stdlib.h> 72#include <unistd.h> 73 74#include "primes.h" 75 76/* 77 * prime[i] is the (i-1)th prime. 78 * 79 * We are able to sieve 2^32-1 because this byte table yields all primes 80 * up to 65537 and 65537^2 > 2^32-1. 81 */ 82extern ubig prime[]; 83extern ubig *pr_limit; /* largest prime in the prime array */ 84 85int hflag; 86 87void pr_fact __P((ubig)); /* print factors of a value */ 88void usage __P((void)); 89 90int 91main(argc, argv) 92 int argc; 93 char *argv[]; 94{ 95 ubig val; 96 int ch; 97 char *p, buf[100]; /* > max number of digits. */ 98 99 while ((ch = getopt(argc, argv, "h")) != -1) 100 switch (ch) { 101 case 'h': 102 hflag++; 103 break; 104 case '?': 105 default: 106 usage(); 107 } 108 argc -= optind; 109 argv += optind; 110 111 /* No args supplied, read numbers from stdin. */ 112 if (argc == 0) 113 for (;;) { 114 if (fgets(buf, sizeof(buf), stdin) == NULL) { 115 if (ferror(stdin)) 116 err(1, "stdin"); 117 exit (0); 118 } 119 for (p = buf; isblank(*p); ++p); 120 if (*p == '\n' || *p == '\0') 121 continue; 122 if (*p == '-') 123 errx(1, "negative numbers aren't permitted."); 124 errno = 0; 125 val = strtoul(buf, &p, 0); 126 if (errno) 127 err(1, "%s", buf); 128 if (*p != '\n') 129 errx(1, "%s: illegal numeric format.", buf); 130 pr_fact(val); 131 } 132 /* Factor the arguments. */ 133 else 134 for (; *argv != NULL; ++argv) { 135 if (argv[0][0] == '-') 136 errx(1, "negative numbers aren't permitted."); 137 errno = 0; 138 val = strtoul(argv[0], &p, 0); 139 if (errno) 140 err(1, "%s", argv[0]); 141 if (*p != '\0') 142 errx(1, "%s: illegal numeric format.", argv[0]); 143 pr_fact(val); 144 } 145 exit(0); 146} 147 148/* 149 * pr_fact - print the factors of a number 150 * 151 * If the number is 0 or 1, then print the number and return. 152 * If the number is < 0, print -1, negate the number and continue 153 * processing. 154 * 155 * Print the factors of the number, from the lowest to the highest. 156 * A factor will be printed numtiple times if it divides the value 157 * multiple times. 158 * 159 * Factors are printed with leading tabs. 160 */ 161void 162pr_fact(val) 163 ubig val; /* Factor this value. */ 164{ 165 ubig *fact; /* The factor found. */ 166 167 /* Firewall - catch 0 and 1. */ 168 if (val == 0) /* Historical practice; 0 just exits. */ 169 exit(0); 170 if (val == 1) { 171 (void)printf("1: 1\n"); 172 return; 173 } 174 175 /* Factor value. */ 176 (void)printf(hflag ? "0x%lx:" : "%lu:", val); 177 for (fact = &prime[0]; val > 1; ++fact) { 178 /* Look for the smallest factor. */ 179 do { 180 if (val % (long)*fact == 0) 181 break; 182 } while (++fact <= pr_limit); 183 184 /* Watch for primes larger than the table. */ 185 if (fact > pr_limit) { 186 (void)printf(hflag ? " 0x%lx" : " %lu", val); 187 break; 188 } 189 190 /* Divide factor out until none are left. */ 191 do { 192 (void)printf(hflag ? " 0x%lx" : " %lu", *fact); 193 val /= *fact; 194 } while ((val % *fact) == 0); 195 196 /* Let the user know we're doing something. */ 197 (void)fflush(stdout); 198 } 199 (void)putchar('\n'); 200} 201 202void 203usage() 204{ 205 (void)fprintf(stderr, "usage: factor -h [value ...]\n"); 206 exit (0); 207} 208