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 * %sccs.include.redist.c% 9 */ 10 11 #ifndef lint 12 static char copyright[] = 13 "@(#) Copyright (c) 1989, 1993\n\ 14 The Regents of the University of California. All rights reserved.\n"; 15 #endif /* not lint */ 16 17 #ifndef lint 18 static char sccsid[] = "@(#)factor.c 8.4 (Berkeley) 05/04/95"; 19 #endif /* not lint */ 20 21 /* 22 * factor - factor a number into primes 23 * 24 * By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo 25 * 26 * chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\ 27 * 28 * usage: 29 * factor [number] ... 30 * 31 * The form of the output is: 32 * 33 * number: factor1 factor1 factor2 factor3 factor3 factor3 ... 34 * 35 * where factor1 < factor2 < factor3 < ... 36 * 37 * If no args are given, the list of numbers are read from stdin. 38 */ 39 40 #include <err.h> 41 #include <ctype.h> 42 #include <errno.h> 43 #include <limits.h> 44 #include <stdio.h> 45 #include <stdlib.h> 46 #include <unistd.h> 47 48 #include "primes.h" 49 50 /* 51 * prime[i] is the (i-1)th prime. 52 * 53 * We are able to sieve 2^32-1 because this byte table yields all primes 54 * up to 65537 and 65537^2 > 2^32-1. 55 */ 56 extern ubig prime[]; 57 extern ubig *pr_limit; /* largest prime in the prime array */ 58 59 void pr_fact __P((ubig)); /* print factors of a value */ 60 void usage __P((void)); 61 62 int 63 main(argc, argv) 64 int argc; 65 char *argv[]; 66 { 67 ubig val; 68 int ch; 69 char *p, buf[100]; /* > max number of digits. */ 70 71 while ((ch = getopt(argc, argv, "")) != EOF) 72 switch (ch) { 73 case '?': 74 default: 75 usage(); 76 } 77 argc -= optind; 78 argv += optind; 79 80 /* No args supplied, read numbers from stdin. */ 81 if (argc == 0) 82 for (;;) { 83 if (fgets(buf, sizeof(buf), stdin) == NULL) { 84 if (ferror(stdin)) 85 err(1, "stdin"); 86 exit (0); 87 } 88 for (p = buf; isblank(*p); ++p); 89 if (*p == '\n' || *p == '\0') 90 continue; 91 if (*p == '-') 92 errx(1, "negative numbers aren't permitted."); 93 errno = 0; 94 val = strtoul(buf, &p, 10); 95 if (errno) 96 err(1, "%s", buf); 97 if (*p != '\n') 98 errx(1, "%s: illegal numeric format.", buf); 99 pr_fact(val); 100 } 101 /* Factor the arguments. */ 102 else 103 for (; *argv != NULL; ++argv) { 104 if (argv[0][0] == '-') 105 errx(1, "negative numbers aren't permitted."); 106 errno = 0; 107 val = strtoul(argv[0], &p, 10); 108 if (errno) 109 err(1, "%s", argv[0]); 110 if (*p != '\0') 111 errx(1, "%s: illegal numeric format.", argv[0]); 112 pr_fact(val); 113 } 114 exit(0); 115 } 116 117 /* 118 * pr_fact - print the factors of a number 119 * 120 * If the number is 0 or 1, then print the number and return. 121 * If the number is < 0, print -1, negate the number and continue 122 * processing. 123 * 124 * Print the factors of the number, from the lowest to the highest. 125 * A factor will be printed numtiple times if it divides the value 126 * multiple times. 127 * 128 * Factors are printed with leading tabs. 129 */ 130 void 131 pr_fact(val) 132 ubig val; /* Factor this value. */ 133 { 134 ubig *fact; /* The factor found. */ 135 136 /* Firewall - catch 0 and 1. */ 137 if (val == 0) /* Historical practice; 0 just exits. */ 138 exit(0); 139 if (val == 1) { 140 (void)printf("1: 1\n"); 141 return; 142 } 143 144 /* Factor value. */ 145 (void)printf("%lu:", val); 146 for (fact = &prime[0]; val > 1; ++fact) { 147 /* Look for the smallest factor. */ 148 do { 149 if (val % (long)*fact == 0) 150 break; 151 } while (++fact <= pr_limit); 152 153 /* Watch for primes larger than the table. */ 154 if (fact > pr_limit) { 155 (void)printf(" %lu", val); 156 break; 157 } 158 159 /* Divide factor out until none are left. */ 160 do { 161 (void)printf(" %lu", *fact); 162 val /= (long)*fact; 163 } while ((val % (long)*fact) == 0); 164 165 /* Let the user know we're doing something. */ 166 (void)fflush(stdout); 167 } 168 (void)putchar('\n'); 169 } 170 171 void 172 usage() 173 { 174 (void)fprintf(stderr, "usage: factor [value ...]\n"); 175 exit (0); 176 } 177