1 /* mpf_div_2exp -- Divide a float by 2^n.
3 Copyright (C) 1993, 1994, 1996 Free Software Foundation, Inc.
5 This file is part of the GNU MP Library.
7 The GNU MP Library is free software; you can redistribute it and/or modify
8 it under the terms of the GNU Library General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or (at your
10 option) any later version.
12 The GNU MP Library is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
15 License for more details.
17 You should have received a copy of the GNU Library General Public License
18 along with the GNU MP Library; see the file COPYING.LIB. If not, write to
19 the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
20 MA 02111-1307, USA. */
27 mpf_div_2exp (mpf_ptr r, mpf_srcptr u, unsigned long int exp)
29 mpf_div_2exp (r, u, exp)
32 unsigned long int exp;
39 mp_size_t prec = r->_mp_prec;
40 mp_exp_t uexp = u->_mp_exp;
51 abs_usize = ABS (usize);
56 up += abs_usize - prec;
60 if (exp % BITS_PER_MP_LIMB == 0)
63 MPN_COPY (rp, up, abs_usize);
64 r->_mp_exp = uexp - exp / BITS_PER_MP_LIMB;
68 /* Use mpn_lshift since mpn_rshift operates upwards, and we therefore
69 would clobber part of U before using that part, when R == U. */
71 cy_limb = mpn_lshift (rp, up, abs_usize, -exp % BITS_PER_MP_LIMB);
72 rp[abs_usize] = cy_limb;
73 cy_limb = cy_limb != 0;
76 r->_mp_exp = uexp - exp / BITS_PER_MP_LIMB - 1 + cy_limb;
78 r->_mp_size = usize >= 0 ? abs_usize : -abs_usize;