1 /* mpz_mul_2exp -- Multiply a bignum by 2**CNT 2 3 Copyright 1991, 1993, 1994, 1996, 2001, 2002 Free Software Foundation, Inc. 4 5 This file is part of the GNU MP Library. 6 7 The GNU MP Library is free software; you can redistribute it and/or modify 8 it under the terms of the GNU Lesser General Public License as published by 9 the Free Software Foundation; either version 3 of the License, or (at your 10 option) any later version. 11 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 Lesser General Public 15 License for more details. 16 17 You should have received a copy of the GNU Lesser General Public License 18 along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ 19 20 #include "gmp.h" 21 #include "gmp-impl.h" 22 23 void 24 mpz_mul_2exp (mpz_ptr w, mpz_srcptr u, mp_bitcnt_t cnt) 25 { 26 mp_size_t usize = u->_mp_size; 27 mp_size_t abs_usize = ABS (usize); 28 mp_size_t wsize; 29 mp_size_t limb_cnt; 30 mp_ptr wp; 31 mp_limb_t wlimb; 32 33 if (usize == 0) 34 { 35 w->_mp_size = 0; 36 return; 37 } 38 39 limb_cnt = cnt / GMP_NUMB_BITS; 40 wsize = abs_usize + limb_cnt + 1; 41 if (w->_mp_alloc < wsize) 42 _mpz_realloc (w, wsize); 43 44 wp = w->_mp_d; 45 wsize = abs_usize + limb_cnt; 46 47 cnt %= GMP_NUMB_BITS; 48 if (cnt != 0) 49 { 50 wlimb = mpn_lshift (wp + limb_cnt, u->_mp_d, abs_usize, cnt); 51 if (wlimb != 0) 52 { 53 wp[wsize] = wlimb; 54 wsize++; 55 } 56 } 57 else 58 { 59 MPN_COPY_DECR (wp + limb_cnt, u->_mp_d, abs_usize); 60 } 61 62 /* Zero all whole limbs at low end. Do it here and not before calling 63 mpn_lshift, not to lose for U == W. */ 64 MPN_ZERO (wp, limb_cnt); 65 66 w->_mp_size = usize >= 0 ? wsize : -wsize; 67 } 68