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 | } |