1 | /* mpz_tdiv_r_2exp -- Divide a integer by 2**CNT and produce a remainder. |
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2 | |
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3 | Copyright (C) 1991, 1993, 1994, 1995 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 | #if __STDC__ |
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27 | mpz_tdiv_r_2exp (mpz_ptr res, mpz_srcptr in, unsigned long int cnt) |
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28 | #else |
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29 | mpz_tdiv_r_2exp (res, in, cnt) |
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30 | mpz_ptr res; |
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31 | mpz_srcptr in; |
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32 | unsigned long int cnt; |
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33 | #endif |
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34 | { |
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35 | mp_size_t in_size = ABS (in->_mp_size); |
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36 | mp_size_t res_size; |
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37 | mp_size_t limb_cnt = cnt / BITS_PER_MP_LIMB; |
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38 | mp_srcptr in_ptr = in->_mp_d; |
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39 | |
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40 | if (in_size > limb_cnt) |
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41 | { |
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42 | /* The input operand is (probably) greater than 2**CNT. */ |
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43 | mp_limb_t x; |
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44 | |
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45 | x = in_ptr[limb_cnt] & (((mp_limb_t) 1 << cnt % BITS_PER_MP_LIMB) - 1); |
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46 | if (x != 0) |
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47 | { |
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48 | res_size = limb_cnt + 1; |
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49 | if (res->_mp_alloc < res_size) |
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50 | _mpz_realloc (res, res_size); |
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51 | |
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52 | res->_mp_d[limb_cnt] = x; |
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53 | } |
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54 | else |
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55 | { |
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56 | res_size = limb_cnt; |
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57 | MPN_NORMALIZE (in_ptr, res_size); |
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58 | |
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59 | if (res->_mp_alloc < res_size) |
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60 | _mpz_realloc (res, res_size); |
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61 | |
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62 | limb_cnt = res_size; |
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63 | } |
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64 | } |
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65 | else |
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66 | { |
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67 | /* The input operand is smaller than 2**CNT. We perform a no-op, |
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68 | apart from that we might need to copy IN to RES. */ |
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69 | res_size = in_size; |
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70 | if (res->_mp_alloc < res_size) |
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71 | _mpz_realloc (res, res_size); |
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72 | |
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73 | limb_cnt = res_size; |
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74 | } |
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75 | |
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76 | if (res != in) |
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77 | MPN_COPY (res->_mp_d, in->_mp_d, limb_cnt); |
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78 | res->_mp_size = in->_mp_size >= 0 ? res_size : -res_size; |
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79 | } |
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