1 /* mpf_set_prec(x) -- Change the precision of x. 2 3 Copyright 1993, 1994, 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 the GNU Lesser General Public License as published by 9 the Free Software Foundation; either version 3 of the License, or (at your 10 option) any later version. 11 12 The GNU MP Library is distributed in the hope that it will be useful, but 13 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 14 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 15 License for more details. 16 17 You should have received a copy of the GNU Lesser General Public License 18 along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ 19 20 #include "gmp.h" 21 #include "gmp-impl.h" 22 23 24 /* A full new_prec+1 limbs are always retained, even though just new_prec 25 would satisfy the requested precision. If size==new_prec+1 then 26 certainly new_prec+1 should be kept since no copying is needed in that 27 case. If just new_prec was kept for size>new_prec+1 it'd be a bit 28 inconsistent. */ 29 30 void 31 mpf_set_prec (mpf_ptr x, unsigned long int new_prec_in_bits) 32 { 33 mp_size_t old_prec, new_prec, new_prec_plus1; 34 mp_size_t size, sign; 35 mp_ptr xp; 36 37 new_prec = __GMPF_BITS_TO_PREC (new_prec_in_bits); 38 old_prec = PREC(x); 39 40 /* do nothing if already the right precision */ 41 if (new_prec == old_prec) 42 return; 43 44 PREC(x) = new_prec; 45 new_prec_plus1 = new_prec + 1; 46 47 /* retain most significant limbs */ 48 sign = SIZ(x); 49 size = ABS (sign); 50 xp = PTR(x); 51 if (size > new_prec_plus1) 52 { 53 SIZ(x) = (sign >= 0 ? new_prec_plus1 : -new_prec_plus1); 54 MPN_COPY_INCR (xp, xp + size - new_prec_plus1, new_prec_plus1); 55 } 56 57 PTR(x) = __GMP_REALLOCATE_FUNC_LIMBS (xp, old_prec+1, new_prec_plus1); 58 } 59