1 /* mpz_mul_2exp -- Multiply a bignum by 2**CNT
3 Copyright (C) 1991, 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 mpz_mul_2exp (mpz_ptr w, mpz_srcptr u, unsigned long int cnt)
29 mpz_mul_2exp (w, u, cnt)
32 unsigned long int cnt;
35 mp_size_t usize = u->_mp_size;
36 mp_size_t abs_usize = ABS (usize);
48 limb_cnt = cnt / BITS_PER_MP_LIMB;
49 wsize = abs_usize + limb_cnt + 1;
50 if (w->_mp_alloc < wsize)
51 _mpz_realloc (w, wsize);
54 wsize = abs_usize + limb_cnt;
56 cnt %= BITS_PER_MP_LIMB;
59 wlimb = mpn_lshift (wp + limb_cnt, u->_mp_d, abs_usize, cnt);
68 MPN_COPY_DECR (wp + limb_cnt, u->_mp_d, abs_usize);
71 /* Zero all whole limbs at low end. Do it here and not before calling
72 mpn_lshift, not to lose for U == W. */
73 MPN_ZERO (wp, limb_cnt);
75 w->_mp_size = usize >= 0 ? wsize : -wsize;