78 lines
1.9 KiB
C
78 lines
1.9 KiB
C
/*=============================================================================
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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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int
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n_remove(mp_limb_t * n, mp_limb_t p)
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{
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int exp, i;
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mp_limb_t powp[6];
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mp_limb_t quot, rem;
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if (p == 2)
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{
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count_trailing_zeros(exp, *n);
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if (exp)
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(*n) >>= exp;
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return exp;
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}
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powp[0] = p;
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for (i = 0; ; i++)
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{
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if ((*n) < powp[i])
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break;
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quot = (*n) / powp[i];
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rem = (*n) - quot * powp[i];
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if (rem != UWORD(0))
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break;
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powp[i + 1] = powp[i] * powp[i];
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(*n) = quot;
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}
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exp = (1 << i) - 1;
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while (i > 0)
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{
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i--;
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if ((*n) < powp[i])
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continue;
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quot = (*n) / powp[i];
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rem = (*n) - quot * powp[i];
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if (rem == UWORD(0))
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{
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exp += (UWORD(1) << i);
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(*n) = quot;
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}
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}
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return exp;
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}
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