tdiv_q_2exp.c
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上传日期:2022-08-06
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- /* mpz_tdiv_q_2exp -- Divide an integer by 2**CNT. Round the quotient
- towards -infinity.
- Copyright 1991, 1993, 1994, 1996, 2001, 2002 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"
- void
- mpz_tdiv_q_2exp (mpz_ptr w, mpz_srcptr u, mp_bitcnt_t cnt)
- {
- mp_size_t usize, wsize;
- mp_size_t limb_cnt;
- usize = u->_mp_size;
- limb_cnt = cnt / GMP_NUMB_BITS;
- wsize = ABS (usize) - limb_cnt;
- if (wsize <= 0)
- w->_mp_size = 0;
- else
- {
- mp_ptr wp;
- mp_srcptr up;
- if (w->_mp_alloc < wsize)
- _mpz_realloc (w, wsize);
- wp = w->_mp_d;
- up = u->_mp_d;
- cnt %= GMP_NUMB_BITS;
- if (cnt != 0)
- {
- mpn_rshift (wp, up + limb_cnt, wsize, cnt);
- wsize -= wp[wsize - 1] == 0;
- }
- else
- {
- MPN_COPY_INCR (wp, up + limb_cnt, wsize);
- }
- w->_mp_size = usize >= 0 ? wsize : -wsize;
- }
- }