| 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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