1/* mpz_cdiv_q_2exp, mpz_fdiv_q_2exp -- quotient from mpz divided by 2^n. 2 3Copyright 1991, 1993, 1994, 1996, 1998, 1999, 2001, 2002, 2004, 2012, 42015 Free Software Foundation, Inc. 5 6This file is part of the GNU MP Library. 7 8The GNU MP Library is free software; you can redistribute it and/or modify 9it under the terms of either: 10 11 * the GNU Lesser General Public License as published by the Free 12 Software Foundation; either version 3 of the License, or (at your 13 option) any later version. 14 15or 16 17 * the GNU General Public License as published by the Free Software 18 Foundation; either version 2 of the License, or (at your option) any 19 later version. 20 21or both in parallel, as here. 22 23The GNU MP Library is distributed in the hope that it will be useful, but 24WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 25or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 26for more details. 27 28You should have received copies of the GNU General Public License and the 29GNU Lesser General Public License along with the GNU MP Library. If not, 30see https://www.gnu.org/licenses/. */ 31 32#include "gmp-impl.h" 33 34 35/* dir==1 for ceil, dir==-1 for floor */ 36 37static void __gmpz_cfdiv_q_2exp (REGPARM_3_1 (mpz_ptr, mpz_srcptr, mp_bitcnt_t, int)) REGPARM_ATTR (1); 38#define cfdiv_q_2exp(w,u,cnt,dir) __gmpz_cfdiv_q_2exp (REGPARM_3_1 (w,u,cnt,dir)) 39 40REGPARM_ATTR (1) static void 41cfdiv_q_2exp (mpz_ptr w, mpz_srcptr u, mp_bitcnt_t cnt, int dir) 42{ 43 mp_size_t wsize, usize, abs_usize, limb_cnt, i; 44 mp_srcptr up; 45 mp_ptr wp; 46 mp_limb_t round, rmask; 47 48 usize = SIZ (u); 49 abs_usize = ABS (usize); 50 limb_cnt = cnt / GMP_NUMB_BITS; 51 wsize = abs_usize - limb_cnt; 52 if (wsize <= 0) 53 { 54 /* u < 2**cnt, so result 1, 0 or -1 according to rounding */ 55 MPZ_NEWALLOC (w, 1)[0] = 1; 56 SIZ(w) = (usize == 0 || (usize ^ dir) < 0 ? 0 : dir); 57 return; 58 } 59 60 /* +1 limb to allow for mpn_add_1 below */ 61 wp = MPZ_REALLOC (w, wsize+1); 62 63 /* Check for rounding if direction matches u sign. 64 Set round if we're skipping non-zero limbs. */ 65 up = PTR(u); 66 round = 0; 67 rmask = ((usize ^ dir) >= 0 ? MP_LIMB_T_MAX : 0); 68 if (rmask != 0) 69 for (i = 0; i < limb_cnt && round == 0; i++) 70 round = up[i]; 71 72 cnt %= GMP_NUMB_BITS; 73 if (cnt != 0) 74 { 75 round |= rmask & mpn_rshift (wp, up + limb_cnt, wsize, cnt); 76 wsize -= (wp[wsize - 1] == 0); 77 } 78 else 79 MPN_COPY_INCR (wp, up + limb_cnt, wsize); 80 81 if (round != 0) 82 { 83 if (wsize != 0) 84 { 85 mp_limb_t cy; 86 cy = mpn_add_1 (wp, wp, wsize, CNST_LIMB(1)); 87 wp[wsize] = cy; 88 wsize += cy; 89 } 90 else 91 { 92 /* We shifted something to zero. */ 93 wp[0] = 1; 94 wsize = 1; 95 } 96 } 97 SIZ(w) = (usize >= 0 ? wsize : -wsize); 98} 99 100 101void 102mpz_cdiv_q_2exp (mpz_ptr w, mpz_srcptr u, mp_bitcnt_t cnt) 103{ 104 cfdiv_q_2exp (w, u, cnt, 1); 105} 106 107void 108mpz_fdiv_q_2exp (mpz_ptr w, mpz_srcptr u, mp_bitcnt_t cnt) 109{ 110 cfdiv_q_2exp (w, u, cnt, -1); 111} 112