59 lines
1.5 KiB
C
59 lines
1.5 KiB
C
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/* mpn_divexact_byff
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dnl Copyright 2009 Jason Moxham
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dnl This file is part of the MPIR Library.
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dnl The MPIR Library is free software; you can redistribute it and/or modify
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dnl it under the terms of the GNU Lesser General Public License as published
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dnl by the Free Software Foundation; either version 2.1 of the License, or (at
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dnl your option) any later version.
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dnl The MPIR Library is distributed in the hope that it will be useful, but
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dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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dnl License for more details.
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dnl You should have received a copy of the GNU Lesser General Public License
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dnl along with the MPIR Library; see the file COPYING.LIB. If not, write
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dnl to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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dnl Boston, MA 02110-1301, USA.
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*/
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#include "mpir.h"
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#include "gmp-impl.h"
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/*
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where (xp,n) = (qp,n)*(B-1) -ret*B^n and 0 <= ret < B-1 B=2^GMP_NUMB_BITS
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This is the standard divexact algorithm with simplifications for the divisior B-1
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*/
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mp_limb_t
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mpn_divexact_byff (mp_ptr qp, mp_srcptr xp, mp_size_t n)
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{
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mp_size_t j;
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mp_limb_t t, a, b;
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ASSERT (n > 0);
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ASSERT_MPN (xp, n);
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ASSERT (MPN_SAME_OR_SEPARATE_P (qp, xp, n));
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a = 0;
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for (j = 0; j <= n - 1; j++)
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{
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t = xp[j];
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if (t > a)
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{
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b = 1;
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}
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else
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{
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b = 0;
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}
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a = a - t;
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qp[j] = a;
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a = a - b; /* no borrow from this sub */
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}
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return a;
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}
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