67 lines
1.7 KiB
C
67 lines
1.7 KiB
C
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/* Determine prime number.
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Copyright (C) 2006 Red Hat, Inc.
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This file is part of elfutils.
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Written by Ulrich Drepper <drepper@redhat.com>, 2000.
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This file is free software; you can redistribute it and/or modify
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it under the terms of either
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* the GNU Lesser General Public License as published by the Free
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Software Foundation; either version 3 of the License, or (at
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your option) any later version
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or
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* the GNU General Public License as published by the Free
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Software Foundation; either version 2 of the License, or (at
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your option) any later version
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or both in parallel, as here.
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elfutils is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received copies of the GNU General Public License and
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the GNU Lesser General Public License along with this program. If
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not, see <http://www.gnu.org/licenses/>. */
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#include <stddef.h>
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/* Test whether CANDIDATE is a prime. */
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static int
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is_prime (size_t candidate)
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{
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/* No even number and none less than 10 will be passed here. */
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size_t divn = 3;
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size_t sq = divn * divn;
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while (sq < candidate && candidate % divn != 0)
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{
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size_t old_sq = sq;
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++divn;
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sq += 4 * divn;
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if (sq < old_sq)
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return 1;
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++divn;
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}
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return candidate % divn != 0;
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}
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/* We need primes for the table size. */
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size_t
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next_prime (size_t seed)
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{
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/* Make it definitely odd. */
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seed |= 1;
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while (!is_prime (seed))
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seed += 2;
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return seed;
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}
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