1 | /* mpz_mul_2exp -- Multiply a bignum by 2**CNT |
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2 | |
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3 | Copyright 1991, 1993, 1994, 1996, 2001, 2002 Free Software Foundation, Inc. |
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4 | |
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5 | This file is part of the GNU MP Library. |
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6 | |
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7 | The GNU MP Library is free software; you can redistribute it and/or modify |
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8 | it under the terms of the GNU Lesser General Public License as published by |
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9 | the Free Software Foundation; either version 2.1 of the License, or (at your |
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10 | option) any later version. |
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11 | |
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12 | The GNU MP Library is distributed in the hope that it will be useful, but |
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13 | WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
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14 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
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15 | License for more details. |
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16 | |
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17 | You should have received a copy of the GNU Lesser General Public License |
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18 | along with the GNU MP Library; see the file COPYING.LIB. If not, write to |
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19 | the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
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20 | MA 02111-1307, USA. */ |
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21 | |
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22 | #include "gmp.h" |
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23 | #include "gmp-impl.h" |
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24 | |
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25 | void |
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26 | mpz_mul_2exp (mpz_ptr w, mpz_srcptr u, unsigned long int cnt) |
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27 | { |
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28 | mp_size_t usize = u->_mp_size; |
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29 | mp_size_t abs_usize = ABS (usize); |
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30 | mp_size_t wsize; |
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31 | mp_size_t limb_cnt; |
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32 | mp_ptr wp; |
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33 | mp_limb_t wlimb; |
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34 | |
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35 | if (usize == 0) |
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36 | { |
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37 | w->_mp_size = 0; |
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38 | return; |
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39 | } |
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40 | |
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41 | limb_cnt = cnt / GMP_NUMB_BITS; |
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42 | wsize = abs_usize + limb_cnt + 1; |
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43 | if (w->_mp_alloc < wsize) |
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44 | _mpz_realloc (w, wsize); |
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45 | |
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46 | wp = w->_mp_d; |
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47 | wsize = abs_usize + limb_cnt; |
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48 | |
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49 | cnt %= GMP_NUMB_BITS; |
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50 | if (cnt != 0) |
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51 | { |
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52 | wlimb = mpn_lshift (wp + limb_cnt, u->_mp_d, abs_usize, cnt); |
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53 | if (wlimb != 0) |
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54 | { |
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55 | wp[wsize] = wlimb; |
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56 | wsize++; |
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57 | } |
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58 | } |
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59 | else |
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60 | { |
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61 | MPN_COPY_DECR (wp + limb_cnt, u->_mp_d, abs_usize); |
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62 | } |
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63 | |
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64 | /* Zero all whole limbs at low end. Do it here and not before calling |
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65 | mpn_lshift, not to lose for U == W. */ |
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66 | MPN_ZERO (wp, limb_cnt); |
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67 | |
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68 | w->_mp_size = usize >= 0 ? wsize : -wsize; |
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69 | } |
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