77 lines
2.1 KiB
C
77 lines
2.1 KiB
C
/* mpn_dc_div_q -- divide-and-conquer division, returning exact quotient
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only.
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Contributed to the GNU project by Torbjorn Granlund and Marco Bodrato.
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THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE. IT IS ONLY
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SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
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GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GMP RELEASE.
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Copyright 2006, 2007, 2009, 2010 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
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#include "mpir.h"
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#include "gmp-impl.h"
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mp_limb_t
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mpn_dc_div_q (mp_ptr qp, mp_ptr np, mp_size_t nn,
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mp_srcptr dp, mp_size_t dn, mp_limb_t dinv)
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{
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mp_ptr tp, wp;
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mp_limb_t qh;
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mp_size_t qn;
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TMP_DECL;
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TMP_MARK;
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ASSERT (dn >= 6);
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ASSERT (nn - dn >= 3);
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ASSERT (dp[dn-1] & GMP_NUMB_HIGHBIT);
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tp = TMP_ALLOC_LIMBS (nn + 1);
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MPN_COPY (tp + 1, np, nn);
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tp[0] = 0;
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qn = nn - dn;
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wp = TMP_ALLOC_LIMBS (qn + 1);
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qh = mpn_dc_divappr_q (wp, tp, nn + 1, dp, dn, dinv);
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if (wp[0] == 0)
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{
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mp_limb_t cy;
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if (qn > dn)
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mpn_mul (tp, wp + 1, qn, dp, dn);
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else
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mpn_mul (tp, dp, dn, wp + 1, qn);
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cy = (qh != 0) ? mpn_add_n (tp + qn, tp + qn, dp, dn) : 0;
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if (cy || mpn_cmp (tp, np, nn) > 0) /* At most is wrong by one, no cycle. */
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qh -= mpn_sub_1 (qp, wp + 1, qn, 1);
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else /* Same as below */
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MPN_COPY (qp, wp + 1, qn);
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}
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else
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MPN_COPY (qp, wp + 1, qn);
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TMP_FREE;
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return qh;
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}
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