1 /* mpn_rshift -- Shift right low level.
3 Copyright 1991, 1993, 1994, 1996, 2000, 2001, 2002 Free Software Foundation,
6 This file is part of the GNU MP Library.
8 The GNU MP Library is free software; you can redistribute it and/or modify
9 it under the terms of the GNU Lesser General Public License as published by
10 the Free Software Foundation; either version 3 of the License, or (at your
11 option) any later version.
13 The GNU MP Library is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
16 License for more details.
18 You should have received a copy of the GNU Lesser General Public License
19 along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
24 /* Shift U (pointed to by up and N limbs long) cnt bits to the right
25 and store the n least significant limbs of the result at rp.
26 The bits shifted out to the right are returned.
29 1. 0 < cnt < GMP_NUMB_BITS.
30 2. If the result is to be written over the input, rp must be <= up.
34 mpn_rshift (mp_ptr rp, mp_srcptr up, mp_size_t n, unsigned int cnt)
36 mp_limb_t high_limb, low_limb;
43 ASSERT (cnt < GMP_NUMB_BITS);
44 ASSERT (MPN_SAME_OR_INCR_P (rp, up, n));
46 tnc = GMP_NUMB_BITS - cnt;
48 retval = (high_limb << tnc) & GMP_NUMB_MASK;
49 low_limb = high_limb >> cnt;
51 for (i = n - 1; i != 0; i--)
54 *rp++ = low_limb | ((high_limb << tnc) & GMP_NUMB_MASK);
55 low_limb = high_limb >> cnt;