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/* mpz_mul_2exp -- Multiply a bignum by 2**CNT
Copyright 1991, 1993, 1994, 1996, 2001, 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 http://www.gnu.org/licenses/. */
#include "gmp.h"
#include "gmp-impl.h"
void
mpz_mul_2exp (mpz_ptr w, mpz_srcptr u, unsigned long int cnt)
{
mp_size_t usize = u->_mp_size;
mp_size_t abs_usize = ABS (usize);
mp_size_t wsize;
mp_size_t limb_cnt;
mp_ptr wp;
mp_limb_t wlimb;
if (usize == 0)
{
w->_mp_size = 0;
return;
}
limb_cnt = cnt / GMP_NUMB_BITS;
wsize = abs_usize + limb_cnt + 1;
if (w->_mp_alloc < wsize)
_mpz_realloc (w, wsize);
wp = w->_mp_d;
wsize = abs_usize + limb_cnt;
cnt %= GMP_NUMB_BITS;
if (cnt != 0)
{
wlimb = mpn_lshift (wp + limb_cnt, u->_mp_d, abs_usize, cnt);
if (wlimb != 0)
{
wp[wsize] = wlimb;
wsize++;
}
}
else
{
MPN_COPY_DECR (wp + limb_cnt, u->_mp_d, abs_usize);
}
/* Zero all whole limbs at low end. Do it here and not before calling
mpn_lshift, not to lose for U == W. */
MPN_ZERO (wp, limb_cnt);
w->_mp_size = usize >= 0 ? wsize : -wsize;
}
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