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/* mpn_rshift -- Shift right low level.
Copyright 1991, 1993, 1994, 1996, 2000-2002 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation; either version 3 of the License, or (at
your option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library. If not, see https://www.gnu.org/licenses/. */
#include "gmp.h"
#include "gmp-impl.h"
/* Shift U (pointed to by up and N limbs long) cnt bits to the right
and store the n least significant limbs of the result at rp.
The bits shifted out to the right are returned.
Argument constraints:
1. 0 < cnt < GMP_NUMB_BITS.
2. If the result is to be written over the input, rp must be <= up.
*/
mp_limb_t
mpn_rshift (mp_ptr rp, mp_srcptr up, mp_size_t n, unsigned int cnt)
{
mp_limb_t high_limb, low_limb;
unsigned int tnc;
mp_size_t i;
mp_limb_t retval;
ASSERT (n >= 1);
ASSERT (cnt >= 1);
ASSERT (cnt < GMP_NUMB_BITS);
ASSERT (MPN_SAME_OR_INCR_P (rp, up, n));
tnc = GMP_NUMB_BITS - cnt;
high_limb = *up++;
retval = (high_limb << tnc) & GMP_NUMB_MASK;
low_limb = high_limb >> cnt;
for (i = n - 1; i != 0; i--)
{
high_limb = *up++;
*rp++ = low_limb | ((high_limb << tnc) & GMP_NUMB_MASK);
low_limb = high_limb >> cnt;
}
*rp = low_limb;
return retval;
}
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