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