| Austin Schuh | dace2a6 | 2020-08-18 10:56:48 -0700 | [diff] [blame] | 1 | /* mpf_set_prec(x) -- Change the precision of x. |
| 2 | |
| 3 | Copyright 1993-1995, 2000, 2001 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 either: |
| 9 | |
| 10 | * the GNU Lesser General Public License as published by the Free |
| 11 | Software Foundation; either version 3 of the License, or (at your |
| 12 | option) any later version. |
| 13 | |
| 14 | or |
| 15 | |
| 16 | * the GNU General Public License as published by the Free Software |
| 17 | Foundation; either version 2 of the License, or (at your option) any |
| 18 | later version. |
| 19 | |
| 20 | or both in parallel, as here. |
| 21 | |
| 22 | The GNU MP Library is distributed in the hope that it will be useful, but |
| 23 | WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
| 24 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 25 | for more details. |
| 26 | |
| 27 | You should have received copies of the GNU General Public License and the |
| 28 | GNU Lesser General Public License along with the GNU MP Library. If not, |
| 29 | see https://www.gnu.org/licenses/. */ |
| 30 | |
| 31 | #include "gmp-impl.h" |
| 32 | |
| 33 | |
| 34 | /* A full new_prec+1 limbs are always retained, even though just new_prec |
| 35 | would satisfy the requested precision. If size==new_prec+1 then |
| 36 | certainly new_prec+1 should be kept since no copying is needed in that |
| 37 | case. If just new_prec was kept for size>new_prec+1 it'd be a bit |
| 38 | inconsistent. */ |
| 39 | |
| 40 | void |
| 41 | mpf_set_prec (mpf_ptr x, mp_bitcnt_t new_prec_in_bits) |
| 42 | { |
| 43 | mp_size_t old_prec, new_prec, new_prec_plus1; |
| 44 | mp_size_t size, sign; |
| 45 | mp_ptr xp; |
| 46 | |
| 47 | new_prec = __GMPF_BITS_TO_PREC (new_prec_in_bits); |
| 48 | old_prec = PREC(x); |
| 49 | |
| 50 | /* do nothing if already the right precision */ |
| 51 | if (new_prec == old_prec) |
| 52 | return; |
| 53 | |
| 54 | PREC(x) = new_prec; |
| 55 | new_prec_plus1 = new_prec + 1; |
| 56 | |
| 57 | /* retain most significant limbs */ |
| 58 | sign = SIZ(x); |
| 59 | size = ABS (sign); |
| 60 | xp = PTR(x); |
| 61 | if (size > new_prec_plus1) |
| 62 | { |
| 63 | SIZ(x) = (sign >= 0 ? new_prec_plus1 : -new_prec_plus1); |
| 64 | MPN_COPY_INCR (xp, xp + size - new_prec_plus1, new_prec_plus1); |
| 65 | } |
| 66 | |
| 67 | PTR(x) = __GMP_REALLOCATE_FUNC_LIMBS (xp, old_prec+1, new_prec_plus1); |
| 68 | } |