1/* mpq_set_f -- set an mpq from an mpf. 2 3Copyright 2000, 2001, 2002 Free Software Foundation, Inc. 4 5This file is part of the GNU MP Library. 6 7The GNU MP Library is free software; you can redistribute it and/or modify 8it under the terms of the GNU Lesser General Public License as published by 9the Free Software Foundation; either version 3 of the License, or (at your 10option) any later version. 11 12The GNU MP Library is distributed in the hope that it will be useful, but 13WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 14or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 15License for more details. 16 17You should have received a copy of the GNU Lesser General Public License 18along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ 19 20#include "gmp.h" 21#include "gmp-impl.h" 22#include "longlong.h" 23 24 25void 26mpq_set_f (mpq_ptr q, mpf_srcptr f) 27{ 28 mp_size_t fexp = EXP(f); 29 mp_ptr fptr = PTR(f); 30 mp_size_t fsize = SIZ(f); 31 mp_size_t abs_fsize = ABS(fsize); 32 mp_limb_t flow; 33 34 if (fsize == 0) 35 { 36 /* set q=0 */ 37 q->_mp_num._mp_size = 0; 38 q->_mp_den._mp_size = 1; 39 q->_mp_den._mp_d[0] = 1; 40 return; 41 } 42 43 /* strip low zero limbs from f */ 44 flow = *fptr; 45 MPN_STRIP_LOW_ZEROS_NOT_ZERO (fptr, abs_fsize, flow); 46 47 if (fexp >= abs_fsize) 48 { 49 /* radix point is to the right of the limbs, no denominator */ 50 mp_ptr num_ptr; 51 52 MPZ_REALLOC (mpq_numref (q), fexp); 53 num_ptr = q->_mp_num._mp_d; 54 MPN_ZERO (num_ptr, fexp - abs_fsize); 55 MPN_COPY (num_ptr + fexp - abs_fsize, fptr, abs_fsize); 56 57 q->_mp_num._mp_size = fsize >= 0 ? fexp : -fexp; 58 q->_mp_den._mp_size = 1; 59 q->_mp_den._mp_d[0] = 1; 60 } 61 else 62 { 63 /* radix point is within or to the left of the limbs, use denominator */ 64 mp_ptr num_ptr, den_ptr; 65 mp_size_t den_size; 66 67 den_size = abs_fsize - fexp; 68 MPZ_REALLOC (mpq_numref (q), abs_fsize); 69 MPZ_REALLOC (mpq_denref (q), den_size+1); 70 num_ptr = q->_mp_num._mp_d; 71 den_ptr = q->_mp_den._mp_d; 72 73 if (flow & 1) 74 { 75 /* no powers of two to strip from numerator */ 76 77 MPN_COPY (num_ptr, fptr, abs_fsize); 78 MPN_ZERO (den_ptr, den_size); 79 den_ptr[den_size] = 1; 80 } 81 else 82 { 83 /* right shift numerator, adjust denominator accordingly */ 84 int shift; 85 86 den_size--; 87 count_trailing_zeros (shift, flow); 88 89 mpn_rshift (num_ptr, fptr, abs_fsize, shift); 90 abs_fsize -= (num_ptr[abs_fsize-1] == 0); 91 92 MPN_ZERO (den_ptr, den_size); 93 den_ptr[den_size] = GMP_LIMB_HIGHBIT >> (shift-1); 94 } 95 96 q->_mp_num._mp_size = fsize >= 0 ? abs_fsize : -abs_fsize; 97 q->_mp_den._mp_size = den_size + 1; 98 } 99} 100