cfdiv_q_2exp.c
上传用户:qaz666999
上传日期:2022-08-06
资源大小:2570k
文件大小:3k
- /* mpz_cdiv_q_2exp, mpz_fdiv_q_2exp -- quotient from mpz divided by 2^n.
- Copyright 1991, 1993, 1994, 1996, 1998, 1999, 2001, 2002, 2004 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"
- /* dir==1 for ceil, dir==-1 for floor */
- static void __gmpz_cfdiv_q_2exp __GMP_PROTO ((REGPARM_3_1 (mpz_ptr, mpz_srcptr, mp_bitcnt_t, int))) REGPARM_ATTR (1);
- #define cfdiv_q_2exp(w,u,cnt,dir) __gmpz_cfdiv_q_2exp (REGPARM_3_1 (w,u,cnt,dir))
- REGPARM_ATTR (1) static void
- cfdiv_q_2exp (mpz_ptr w, mpz_srcptr u, mp_bitcnt_t cnt, int dir)
- {
- mp_size_t wsize, usize, abs_usize, limb_cnt, i;
- mp_srcptr up;
- mp_ptr wp;
- mp_limb_t round, rmask;
- usize = SIZ (u);
- abs_usize = ABS (usize);
- limb_cnt = cnt / GMP_NUMB_BITS;
- wsize = abs_usize - limb_cnt;
- if (wsize <= 0)
- {
- /* u < 2**cnt, so result 1, 0 or -1 according to rounding */
- PTR(w)[0] = 1;
- SIZ(w) = (usize == 0 || (usize ^ dir) < 0 ? 0 : dir);
- return;
- }
- /* +1 limb to allow for mpn_add_1 below */
- MPZ_REALLOC (w, wsize+1);
- /* Check for rounding if direction matches u sign.
- Set round if we're skipping non-zero limbs. */
- up = PTR(u);
- round = 0;
- rmask = ((usize ^ dir) >= 0 ? MP_LIMB_T_MAX : 0);
- if (rmask != 0)
- for (i = 0; i < limb_cnt && round == 0; i++)
- round = up[i];
- wp = PTR(w);
- cnt %= GMP_NUMB_BITS;
- if (cnt != 0)
- {
- round |= rmask & mpn_rshift (wp, up + limb_cnt, wsize, cnt);
- wsize -= (wp[wsize - 1] == 0);
- }
- else
- MPN_COPY_INCR (wp, up + limb_cnt, wsize);
- if (round != 0)
- {
- if (wsize != 0)
- {
- mp_limb_t cy;
- cy = mpn_add_1 (wp, wp, wsize, CNST_LIMB(1));
- wp[wsize] = cy;
- wsize += cy;
- }
- else
- {
- /* We shifted something to zero. */
- wp[0] = 1;
- wsize = 1;
- }
- }
- SIZ(w) = (usize >= 0 ? wsize : -wsize);
- }
- void
- mpz_cdiv_q_2exp (mpz_ptr w, mpz_srcptr u, mp_bitcnt_t cnt)
- {
- cfdiv_q_2exp (w, u, cnt, 1);
- }
- void
- mpz_fdiv_q_2exp (mpz_ptr w, mpz_srcptr u, mp_bitcnt_t cnt)
- {
- cfdiv_q_2exp (w, u, cnt, -1);
- }