1 /* mpq_set_f -- set an mpq from an mpf. 2 3 Copyright 2000, 2001, 2002 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 #include "longlong.h" 23 24 25 void 26 mpq_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