61 lines
1.7 KiB
C
61 lines
1.7 KiB
C
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/*=============================================================================
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This file is part of FLINT.
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FLINT 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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FLINT 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 FLINT; 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) 2009 William Hart
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******************************************************************************/
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#include <gmp.h>
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#include "flint.h"
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#include "ulong_extras.h"
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mp_limb_t
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n_powmod2_ui_preinv(mp_limb_t a, mp_limb_t exp, mp_limb_t n, mp_limb_t ninv)
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{
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mp_limb_t x, y;
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if (n == UWORD(1)) return UWORD(0);
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x = UWORD(1);
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y = a;
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while (exp)
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{
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if (exp & 1) x = n_mulmod2_preinv(x, y, n, ninv);
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exp >>= 1;
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if (exp) y = n_mulmod2_preinv(y, y, n, ninv);
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}
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return x;
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}
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mp_limb_t
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n_powmod2_preinv(mp_limb_t a, mp_limb_signed_t exp, mp_limb_t n, mp_limb_t ninv)
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{
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if (exp < WORD(0))
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{
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a = n_invmod(a, n);
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exp = -exp;
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}
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return n_powmod2_ui_preinv(a, exp, n, ninv);
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}
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