divexact.c
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上传日期:2022-08-06
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- /* mpz_divexact -- finds quotient when known that quot * den == num && den != 0.
- Contributed to the GNU project by Niels M鰈ler.
- Copyright 1991, 1993, 1994, 1995, 1996, 1997, 1998, 2000, 2001, 2002, 2005,
- 2006, 2007, 2009 Free Software Foundation, Inc.
- This file is part of the GNU MP Library.
- The GNU MP Library is free software; you can redistribute it and/or modify
- it under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 3 of the License, or (at your
- option) any later version.
- The GNU MP Library is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
- License for more details.
- You should have received a copy of the GNU Lesser General Public License
- along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
- #include "gmp.h"
- #include "gmp-impl.h"
- #include "longlong.h"
- void
- mpz_divexact (mpz_ptr quot, mpz_srcptr num, mpz_srcptr den)
- {
- mp_ptr qp;
- mp_size_t qn;
- mp_srcptr np, dp;
- mp_size_t nn, dn;
- TMP_DECL;
- #if WANT_ASSERT
- {
- mpz_t rem;
- mpz_init (rem);
- mpz_tdiv_r (rem, num, den);
- ASSERT (SIZ(rem) == 0);
- mpz_clear (rem);
- }
- #endif
- nn = ABSIZ (num);
- dn = ABSIZ (den);
- qn = nn - dn + 1;
- MPZ_REALLOC (quot, qn);
- if (nn < dn)
- {
- /* This special case avoids segfaults below when the function is
- incorrectly called with |N| < |D|, N != 0. It also handles the
- well-defined case N = 0. */
- SIZ(quot) = 0;
- return;
- }
- TMP_MARK;
- qp = PTR(quot);
- if (quot == num || quot == den)
- qp = TMP_ALLOC_LIMBS (qn);
- np = PTR(num);
- dp = PTR(den);
- mpn_divexact (qp, np, nn, dp, dn);
- MPN_NORMALIZE (qp, qn);
- SIZ(quot) = (SIZ(num) ^ SIZ(den)) >= 0 ? qn : -qn;
- if (qp != PTR(quot))
- MPN_COPY (PTR(quot), qp, qn);
- TMP_FREE;
- }