| File: | src/games/primes/primes.c |
| Warning: | line 116, column 2 Value stored to 'start' is never read |
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| 1 | /* $OpenBSD: primes.c,v 1.24 2017/11/02 10:37:11 tb Exp $ */ |
| 2 | /* $NetBSD: primes.c,v 1.5 1995/04/24 12:24:47 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. Neither the name of the University nor the names of its contributors |
| 20 | * may be used to endorse or promote products derived from this software |
| 21 | * without specific prior written permission. |
| 22 | * |
| 23 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| 24 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 25 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 26 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| 27 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 28 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 29 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 30 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 31 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 32 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 33 | * SUCH DAMAGE. |
| 34 | */ |
| 35 | |
| 36 | /* |
| 37 | * primes - generate a table of primes between two values |
| 38 | * |
| 39 | * By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo |
| 40 | * |
| 41 | * chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\ |
| 42 | * |
| 43 | * usage: |
| 44 | * primes [start [stop]] |
| 45 | * |
| 46 | * Print primes >= start and < stop. If stop is omitted, |
| 47 | * the value 4294967295 (2^32-1) is assumed. If start is |
| 48 | * omitted, start is read from standard input. |
| 49 | * |
| 50 | * validation check: there are 664579 primes between 0 and 10^7 |
| 51 | */ |
| 52 | |
| 53 | #include <ctype.h> |
| 54 | #include <err.h> |
| 55 | #include <math.h> |
| 56 | #include <stdio.h> |
| 57 | #include <stdlib.h> |
| 58 | #include <string.h> |
| 59 | #include <unistd.h> |
| 60 | |
| 61 | #include "primes.h" |
| 62 | |
| 63 | /* |
| 64 | * Eratosthenes sieve table |
| 65 | * |
| 66 | * We only sieve the odd numbers. The base of our sieve windows is always odd. |
| 67 | * If the base of the table is 1, table[i] represents 2*i-1. After the sieve, |
| 68 | * table[i] == 1 if and only if 2*i-1 is prime. |
| 69 | * |
| 70 | * We make TABSIZE large to reduce the overhead of inner loop setup. |
| 71 | */ |
| 72 | char table[TABSIZE256*1024]; /* Eratosthenes sieve of odd numbers */ |
| 73 | |
| 74 | /* |
| 75 | * prime[i] is the (i+1)th prime. |
| 76 | * |
| 77 | * We are able to sieve 2^32-1 because this byte table yields all primes |
| 78 | * up to 65537 and 65537^2 > 2^32-1. |
| 79 | */ |
| 80 | extern const ubig prime[]; |
| 81 | extern const ubig *pr_limit; /* largest prime in the prime array */ |
| 82 | |
| 83 | /* |
| 84 | * To avoid excessive sieves for small factors, we use the table below to |
| 85 | * setup our sieve blocks. Each element represents an odd number starting |
| 86 | * with 1. All non-zero elements are coprime to 3, 5, 7, 11 and 13. |
| 87 | */ |
| 88 | extern const char pattern[]; |
| 89 | extern const int pattern_size; /* length of pattern array */ |
| 90 | |
| 91 | void primes(ubig, ubig); |
| 92 | ubig read_num_buf(void); |
| 93 | __dead__attribute__((__noreturn__)) void usage(void); |
| 94 | |
| 95 | int |
| 96 | main(int argc, char *argv[]) |
| 97 | { |
| 98 | const char *errstr; |
| 99 | ubig start; /* where to start generating */ |
| 100 | ubig stop; /* don't generate at or above this value */ |
| 101 | int ch; |
| 102 | |
| 103 | if (pledge("stdio", NULL((void *)0)) == -1) |
| 104 | err(1, "pledge"); |
| 105 | |
| 106 | while ((ch = getopt(argc, argv, "h")) != -1) { |
| 107 | switch (ch) { |
| 108 | case 'h': |
| 109 | default: |
| 110 | usage(); |
| 111 | } |
| 112 | } |
| 113 | argc -= optind; |
| 114 | argv += optind; |
| 115 | |
| 116 | start = 0; |
Value stored to 'start' is never read | |
| 117 | stop = BIG0xffffffffU; |
| 118 | |
| 119 | switch (argc) { |
| 120 | case 2: |
| 121 | stop = strtonum(argv[1], 0, BIG0xffffffffU, &errstr); |
| 122 | if (errstr) |
| 123 | errx(1, "stop is %s: %s", errstr, argv[1]); |
| 124 | case 1: /* FALLTHROUGH */ |
| 125 | start = strtonum(argv[0], 0, BIG0xffffffffU, &errstr); |
| 126 | if (errstr) |
| 127 | errx(1, "start is %s: %s", errstr, argv[0]); |
| 128 | break; |
| 129 | case 0: |
| 130 | start = read_num_buf(); |
| 131 | break; |
| 132 | default: |
| 133 | usage(); |
| 134 | } |
| 135 | |
| 136 | if (start > stop) |
| 137 | errx(1, "start value must be less than stop value."); |
| 138 | primes(start, stop); |
| 139 | return 0; |
| 140 | } |
| 141 | |
| 142 | /* |
| 143 | * read_num_buf -- |
| 144 | * This routine returns a number n, where 0 <= n && n <= BIG. |
| 145 | */ |
| 146 | ubig |
| 147 | read_num_buf(void) |
| 148 | { |
| 149 | const char *errstr; |
| 150 | ubig val; |
| 151 | char *p, buf[100]; /* > max number of digits. */ |
| 152 | |
| 153 | for (;;) { |
| 154 | if (fgets(buf, sizeof(buf), stdin(&__sF[0])) == NULL((void *)0)) { |
| 155 | if (ferror(stdin)(!__isthreaded ? ((((&__sF[0]))->_flags & 0x0040) != 0) : (ferror)((&__sF[0])))) |
| 156 | err(1, "stdin"); |
| 157 | exit(0); |
| 158 | } |
| 159 | buf[strcspn(buf, "\n")] = '\0'; |
| 160 | for (p = buf; isblank((unsigned char)*p); ++p) |
| 161 | ; |
| 162 | if (*p == '\0') |
| 163 | continue; |
| 164 | val = strtonum(buf, 0, BIG0xffffffffU, &errstr); |
| 165 | if (errstr) |
| 166 | errx(1, "start is %s: %s", errstr, buf); |
| 167 | return (val); |
| 168 | } |
| 169 | } |
| 170 | |
| 171 | /* |
| 172 | * primes - sieve and print primes from start up to and but not including stop |
| 173 | * start: where to start generating |
| 174 | * stop : don't generate at or above this value |
| 175 | */ |
| 176 | void |
| 177 | primes(ubig start, ubig stop) |
| 178 | { |
| 179 | char *q; /* sieve spot */ |
| 180 | ubig factor; /* index and factor */ |
| 181 | char *tab_lim; /* the limit to sieve on the table */ |
| 182 | const ubig *p; /* prime table pointer */ |
| 183 | ubig fact_lim; /* highest prime for current block */ |
| 184 | ubig mod; |
| 185 | |
| 186 | /* |
| 187 | * A number of systems can not convert double values into unsigned |
| 188 | * longs when the values are larger than the largest signed value. |
| 189 | * We don't have this problem, so we can go all the way to BIG. |
| 190 | */ |
| 191 | if (start < 3) { |
| 192 | start = (ubig)2; |
| 193 | } |
| 194 | if (stop < 3) { |
| 195 | stop = (ubig)2; |
| 196 | } |
| 197 | if (stop <= start) { |
| 198 | return; |
| 199 | } |
| 200 | |
| 201 | /* |
| 202 | * be sure that the values are odd, or 2 |
| 203 | */ |
| 204 | if (start != 2 && (start&0x1) == 0) { |
| 205 | ++start; |
| 206 | } |
| 207 | if (stop != 2 && (stop&0x1) == 0) { |
| 208 | ++stop; |
| 209 | } |
| 210 | |
| 211 | /* |
| 212 | * quick list of primes <= pr_limit |
| 213 | */ |
| 214 | if (start <= *pr_limit) { |
| 215 | /* skip primes up to the start value */ |
| 216 | for (p = &prime[0], factor = prime[0]; |
| 217 | factor < stop && p <= pr_limit; factor = *(++p)) { |
| 218 | if (factor >= start) { |
| 219 | printf("%lu\n", (unsigned long) factor); |
| 220 | } |
| 221 | } |
| 222 | /* return early if we are done */ |
| 223 | if (p <= pr_limit) { |
| 224 | return; |
| 225 | } |
| 226 | start = *pr_limit+2; |
| 227 | } |
| 228 | |
| 229 | /* |
| 230 | * we shall sieve a bytemap window, note primes and move the window |
| 231 | * upward until we pass the stop point |
| 232 | */ |
| 233 | while (start < stop) { |
| 234 | /* |
| 235 | * factor out 3, 5, 7, 11 and 13 |
| 236 | */ |
| 237 | /* initial pattern copy */ |
| 238 | factor = (start%(2*3*5*7*11*13))/2; /* starting copy spot */ |
| 239 | memcpy(table, &pattern[factor], pattern_size-factor); |
| 240 | /* main block pattern copies */ |
| 241 | for (fact_lim=pattern_size-factor; |
| 242 | fact_lim+pattern_size<=TABSIZE256*1024; fact_lim+=pattern_size) { |
| 243 | memcpy(&table[fact_lim], pattern, pattern_size); |
| 244 | } |
| 245 | /* final block pattern copy */ |
| 246 | memcpy(&table[fact_lim], pattern, TABSIZE256*1024-fact_lim); |
| 247 | |
| 248 | /* |
| 249 | * sieve for primes 17 and higher |
| 250 | */ |
| 251 | /* note highest useful factor and sieve spot */ |
| 252 | if (stop-start > TABSIZE256*1024+TABSIZE256*1024) { |
| 253 | tab_lim = &table[TABSIZE256*1024]; /* sieve it all */ |
| 254 | fact_lim = (int)sqrt( |
| 255 | (double)(start)+TABSIZE256*1024+TABSIZE256*1024+1.0); |
| 256 | } else { |
| 257 | tab_lim = &table[(stop-start)/2]; /* partial sieve */ |
| 258 | fact_lim = (int)sqrt((double)(stop)+1.0); |
| 259 | } |
| 260 | /* sieve for factors >= 17 */ |
| 261 | factor = 17; /* 17 is first prime to use */ |
| 262 | p = &prime[7]; /* 19 is next prime, pi(19)=7 */ |
| 263 | do { |
| 264 | /* determine the factor's initial sieve point */ |
| 265 | mod = start % factor; |
| 266 | if (mod & 0x1) |
| 267 | q = &table[(factor - mod)/2]; |
| 268 | else |
| 269 | q = &table[mod ? factor-(mod/2) : 0]; |
| 270 | /* sieve for our current factor */ |
| 271 | for ( ; q < tab_lim; q += factor) { |
| 272 | *q = '\0'; /* sieve out a spot */ |
| 273 | } |
| 274 | } while ((factor=(ubig)(*(p++))) <= fact_lim); |
| 275 | |
| 276 | /* |
| 277 | * print generated primes |
| 278 | */ |
| 279 | for (q = table; q < tab_lim; ++q, start+=2) { |
| 280 | if (*q) { |
| 281 | printf("%lu\n", (unsigned long) start); |
| 282 | } |
| 283 | } |
| 284 | } |
| 285 | } |
| 286 | |
| 287 | void |
| 288 | usage(void) |
| 289 | { |
| 290 | (void)fprintf(stderr(&__sF[2]), "usage: %s [start [stop]]\n", getprogname()); |
| 291 | exit(1); |
| 292 | } |