mirror of
https://github.com/vale981/arb
synced 2025-03-06 01:41:39 -05:00
57 lines
1.8 KiB
C
57 lines
1.8 KiB
C
/*=============================================================================
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This file is part of ARB.
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ARB is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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ARB is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with ARB; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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=============================================================================*/
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/******************************************************************************
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Copyright (C) 2016 Pascal Molin
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******************************************************************************/
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#include "dlog.h"
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ulong
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dlog_mod2e(const dlog_modpe_t t, ulong b1)
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{
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if (t->e == 2)
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return (b1 % 4) == 3;
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else
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{
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slong f;
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ulong pf1, pf, x, xf;
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pf1 = 1;
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pf = 4;
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x = 0;
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for (f = 2; f < t->e; f++)
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{
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if (b1 % pf != 1)
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{
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flint_printf("ERROR dlog_mod2e: %wu %% %wu != 1 mod %wu\n\n",
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b1, pf, t->pe.n);
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abort();
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}
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xf = (b1 - 1) / pf;
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xf = (f == 2) ? xf % 4 : (xf % 2) * (pf1 / 2);
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b1 = nmod_mul(b1, nmod_pow_ui(t->inva, xf, t->pe), t->pe);
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x += xf;
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pf1 = pf;
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pf *= 2;
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}
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return x;
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}
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}
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