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Annotation of OpenXM_contrib/gmp/mpq/set_f.c, Revision 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: }