1 /* mpn_rshift -- Shift right a low-level natural-number integer.
3 Copyright (C) 1991 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 General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 The GNU MP Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with the GNU MP Library; see the file COPYING. If not, write to
19 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
24 /* Shift U (pointed to by UP and USIZE limbs long) CNT bits to the right
25 and store the USIZE least significant limbs of the result at WP.
26 Return the size of the result.
29 0. U must be normalized (i.e. it's most significant limb != 0).
30 1. 0 <= CNT < BITS_PER_MP_LIMB
31 2. If the result is to be written over the input, WP must be <= UP.
36 mpn_rshift (mp_ptr wp,
37 mp_srcptr up, mp_size usize,
40 mpn_rshift (wp, up, usize, cnt)
47 mp_limb high_limb, low_limb;
48 /* The following #ifdef hackery is from Lennart (0.999.6) [WDP 94/10] */
49 /* bug in the c compiler */
66 /* Copy from low end to high end, to allow specified input/output
68 for (i = 0; i < usize; i++)
75 sh_2 = BITS_PER_MP_LIMB - sh_1;
79 *cy_limb = high_limb << sh_2;
83 for (i = 1; i < usize; i++)
86 wp[i] = (low_limb >> sh_1) | (high_limb << sh_2);