1/* mpfr_set_ui_2exp -- set a MPFR number from a machine unsigned integer with
2   a shift
3
4Copyright 2004, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
5Contributed by the AriC and Caramel projects, INRIA.
6
7This file is part of the GNU MPFR Library.
8
9The GNU MPFR Library is free software; you can redistribute it and/or modify
10it under the terms of the GNU Lesser General Public License as published by
11the Free Software Foundation; either version 3 of the License, or (at your
12option) any later version.
13
14The GNU MPFR Library is distributed in the hope that it will be useful, but
15WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
16or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
17License for more details.
18
19You should have received a copy of the GNU Lesser General Public License
20along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
21http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
2251 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
23
24#define MPFR_NEED_LONGLONG_H
25#include "mpfr-impl.h"
26
27int
28mpfr_set_ui_2exp (mpfr_ptr x, unsigned long i, mpfr_exp_t e, mpfr_rnd_t rnd_mode)
29{
30  MPFR_SET_POS (x);
31
32  if (i == 0)
33    {
34      MPFR_SET_ZERO (x);
35      MPFR_RET (0);
36    }
37  else
38    {
39      mp_size_t xn;
40      unsigned int cnt, nbits;
41      mp_limb_t *xp;
42      int inex = 0;
43
44      /* FIXME: support int limbs (e.g. 16-bit limbs on 16-bit proc) */
45      MPFR_ASSERTD (i == (mp_limb_t) i);
46
47      /* Position of the highest limb */
48      xn = (MPFR_PREC (x) - 1) / GMP_NUMB_BITS;
49      count_leading_zeros (cnt, (mp_limb_t) i);
50      MPFR_ASSERTD (cnt < GMP_NUMB_BITS);  /* OK since i != 0 */
51
52      xp = MPFR_MANT(x);
53      xp[xn] = ((mp_limb_t) i) << cnt;
54      /* Zero the xn lower limbs. */
55      MPN_ZERO(xp, xn);
56
57      nbits = GMP_NUMB_BITS - cnt;
58      e += nbits;  /* exponent _before_ the rounding */
59
60      /* round if MPFR_PREC(x) smaller than length of i */
61      if (MPFR_UNLIKELY (MPFR_PREC (x) < nbits) &&
62          MPFR_UNLIKELY (mpfr_round_raw (xp + xn, xp + xn, nbits, 0,
63                                         MPFR_PREC (x), rnd_mode, &inex)))
64        {
65          e++;
66          xp[xn] = MPFR_LIMB_HIGHBIT;
67        }
68
69      MPFR_EXP (x) = e;
70      return mpfr_check_range (x, inex, rnd_mode);
71    }
72}
73