Return to set_f.c CVS log

Up to [local] / OpenXM_contrib / gmp / mpq

Annotation of OpenXM_contrib/gmp/mpq/set_f.c, Revision 1.1.1.1

1.1       ohara       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 2.1 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; see the file COPYING.LIB.  If not, write to
                     19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     20: MA 02111-1307, USA. */
                     21:
                     22: #include "gmp.h"
                     23: #include "gmp-impl.h"
                     24: #include "longlong.h"
                     25:
                     26:
                     27: void
                     28: mpq_set_f (mpq_ptr q, mpf_srcptr f)
                     29: {
                     30:   mp_size_t  fexp = EXP(f);
                     31:   mp_ptr     fptr = PTR(f);
                     32:   mp_size_t  fsize = SIZ(f);
                     33:   mp_size_t  abs_fsize = ABS(fsize);
                     34:   mp_limb_t  flow;
                     35:
                     36:   if (fsize == 0)
                     37:     {
                     38:       /* set q=0 */
                     39:       q->_mp_num._mp_size = 0;
                     40:       q->_mp_den._mp_size = 1;
                     41:       q->_mp_den._mp_d[0] = 1;
                     42:       return;
                     43:     }
                     44:
                     45:   /* strip low zero limbs from f */
                     46:   flow = *fptr;
                     47:   MPN_STRIP_LOW_ZEROS_NOT_ZERO (fptr, abs_fsize, flow);
                     48:
                     49:   if (fexp >= abs_fsize)
                     50:     {
                     51:       /* radix point is to the right of the limbs, no denominator */
                     52:       mp_ptr  num_ptr;
                     53:
                     54:       MPZ_REALLOC (mpq_numref (q), fexp);
                     55:       num_ptr = q->_mp_num._mp_d;
                     56:       MPN_ZERO (num_ptr, fexp - abs_fsize);
                     57:       MPN_COPY (num_ptr + fexp - abs_fsize, fptr, abs_fsize);
                     58:
                     59:       q->_mp_num._mp_size = fsize >= 0 ? fexp : -fexp;
                     60:       q->_mp_den._mp_size = 1;
                     61:       q->_mp_den._mp_d[0] = 1;
                     62:     }
                     63:   else
                     64:     {
                     65:       /* radix point is within or to the left of the limbs, use demominator */
                     66:       mp_ptr     num_ptr, den_ptr;
                     67:       mp_size_t  den_size;
                     68:
                     69:       den_size = abs_fsize - fexp;
                     70:       MPZ_REALLOC (mpq_numref (q), abs_fsize);
                     71:       MPZ_REALLOC (mpq_denref (q), den_size+1);
                     72:       num_ptr = q->_mp_num._mp_d;
                     73:       den_ptr = q->_mp_den._mp_d;
                     74:
                     75:       if (flow & 1)
                     76:         {
                     77:           /* no powers of two to strip from numerator */
                     78:
                     79:           MPN_COPY (num_ptr, fptr, abs_fsize);
                     80:           MPN_ZERO (den_ptr, den_size);
                     81:           den_ptr[den_size] = 1;
                     82:         }
                     83:       else
                     84:         {
                     85:           /* right shift numerator, adjust denominator accordingly */
                     86:           int  shift;
                     87:
                     88:           den_size--;
                     89:           count_trailing_zeros (shift, flow);
                     90:
                     91:           mpn_rshift (num_ptr, fptr, abs_fsize, shift);
                     92:           abs_fsize -= (num_ptr[abs_fsize-1] == 0);
                     93:
                     94:           MPN_ZERO (den_ptr, den_size);
                     95:           den_ptr[den_size] = GMP_LIMB_HIGHBIT >> (shift-1);
                     96:         }
                     97:
                     98:       q->_mp_num._mp_size = fsize >= 0 ? abs_fsize : -abs_fsize;
                     99:       q->_mp_den._mp_size = den_size + 1;
                    100:     }
                    101: }