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Ben Cheng25b3c042013-11-20 14:45:36 -08001/* Determine prime number.
2 Copyright (C) 2006 Red Hat, Inc.
Elliott Hughes03333822015-02-18 22:19:45 -08003 This file is part of elfutils.
Ben Cheng25b3c042013-11-20 14:45:36 -08004 Written by Ulrich Drepper <drepper@redhat.com>, 2000.
5
Elliott Hughes03333822015-02-18 22:19:45 -08006 This file is free software; you can redistribute it and/or modify
7 it under the terms of either
Ben Cheng25b3c042013-11-20 14:45:36 -08008
Elliott Hughes03333822015-02-18 22:19:45 -08009 * the GNU Lesser General Public License as published by the Free
10 Software Foundation; either version 3 of the License, or (at
11 your option) any later version
12
13 or
14
15 * the GNU General Public License as published by the Free
16 Software Foundation; either version 2 of the License, or (at
17 your option) any later version
18
19 or both in parallel, as here.
20
21 elfutils is distributed in the hope that it will be useful, but
Ben Cheng25b3c042013-11-20 14:45:36 -080022 WITHOUT ANY WARRANTY; without even the implied warranty of
23 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
24 General Public License for more details.
25
Elliott Hughes03333822015-02-18 22:19:45 -080026 You should have received copies of the GNU General Public License and
27 the GNU Lesser General Public License along with this program. If
28 not, see <http://www.gnu.org/licenses/>. */
Ben Cheng25b3c042013-11-20 14:45:36 -080029
30#include <stddef.h>
31
32
33/* Test whether CANDIDATE is a prime. */
34static int
35is_prime (size_t candidate)
36{
37 /* No even number and none less than 10 will be passed here. */
38 size_t divn = 3;
39 size_t sq = divn * divn;
40
41 while (sq < candidate && candidate % divn != 0)
42 {
43 size_t old_sq = sq;
44 ++divn;
45 sq += 4 * divn;
46 if (sq < old_sq)
47 return 1;
48 ++divn;
49 }
50
51 return candidate % divn != 0;
52}
53
54
55/* We need primes for the table size. */
56size_t
57next_prime (size_t seed)
58{
59 /* Make it definitely odd. */
60 seed |= 1;
61
62 while (!is_prime (seed))
63 seed += 2;
64
65 return seed;
66}