1 | /* mpf_set_prec(x) -- Change the precision of x. |
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2 | |
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3 | Copyright 1993, 1994, 1995, 2000, 2001 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 | |
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26 | /* A full new_prec+1 limbs are always retained, even though just new_prec |
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27 | would satisfy the requested precision. If size==new_prec+1 then |
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28 | certainly new_prec+1 should be kept since no copying is needed in that |
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29 | case. If just new_prec was kept for size>new_prec+1 it'd be a bit |
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30 | inconsistent. */ |
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31 | |
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32 | void |
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33 | mpf_set_prec (mpf_ptr x, unsigned long int new_prec_in_bits) |
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34 | { |
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35 | mp_size_t old_prec, new_prec, new_prec_plus1; |
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36 | mp_size_t size, sign; |
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37 | mp_ptr xp; |
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38 | |
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39 | new_prec = __GMPF_BITS_TO_PREC (new_prec_in_bits); |
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40 | old_prec = PREC(x); |
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41 | |
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42 | /* do nothing if already the right precision */ |
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43 | if (new_prec == old_prec) |
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44 | return; |
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45 | |
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46 | PREC(x) = new_prec; |
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47 | new_prec_plus1 = new_prec + 1; |
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48 | |
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49 | /* retain most significant limbs */ |
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50 | sign = SIZ(x); |
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51 | size = ABS (sign); |
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52 | xp = PTR(x); |
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53 | if (size > new_prec_plus1) |
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54 | { |
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55 | SIZ(x) = (sign >= 0 ? new_prec_plus1 : -new_prec_plus1); |
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56 | MPN_COPY_INCR (xp, xp + size - new_prec_plus1, new_prec_plus1); |
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57 | } |
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58 | |
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59 | PTR(x) = __GMP_REALLOCATE_FUNC_LIMBS (xp, old_prec+1, new_prec_plus1); |
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60 | } |
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