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Annotation of OpenXM_contrib/gmp/mpf/div.c, Revision 1.1.1.3

1.1       maekawa     1: /* mpf_div -- Divide two floats.
                      2:
1.1.1.3 ! ohara       3: Copyright 1993, 1994, 1996, 2000, 2001, 2002 Free Software Foundation, Inc.
1.1       maekawa     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
1.1.1.2   maekawa     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
1.1       maekawa    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
1.1.1.2   maekawa    14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
1.1       maekawa    15: License for more details.
                     16:
1.1.1.2   maekawa    17: You should have received a copy of the GNU Lesser General Public License
1.1       maekawa    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: void
                     27: mpf_div (mpf_ptr r, mpf_srcptr u, mpf_srcptr v)
                     28: {
                     29:   mp_srcptr up, vp;
                     30:   mp_ptr rp, tp, rtp;
                     31:   mp_size_t usize, vsize;
                     32:   mp_size_t rsize, tsize;
                     33:   mp_size_t sign_quotient;
                     34:   mp_size_t prec;
                     35:   mp_limb_t q_limb;
                     36:   mp_exp_t rexp;
                     37:   TMP_DECL (marker);
                     38:
                     39:   usize = u->_mp_size;
                     40:   vsize = v->_mp_size;
                     41:   sign_quotient = usize ^ vsize;
                     42:   usize = ABS (usize);
                     43:   vsize = ABS (vsize);
                     44:   prec = r->_mp_prec;
                     45:
                     46:   if (vsize == 0)
1.1.1.2   maekawa    47:     DIVIDE_BY_ZERO;
                     48:
1.1       maekawa    49:   if (usize == 0)
                     50:     {
                     51:       r->_mp_size = 0;
                     52:       r->_mp_exp = 0;
                     53:       return;
                     54:     }
                     55:
                     56:   TMP_MARK (marker);
                     57:   rexp = u->_mp_exp - v->_mp_exp;
                     58:
                     59:   rp = r->_mp_d;
                     60:   up = u->_mp_d;
                     61:   vp = v->_mp_d;
                     62:
                     63:   if (vsize > prec)
                     64:     {
                     65:       vp += vsize - prec;
                     66:       vsize = prec;
                     67:     }
                     68:
                     69:   tsize = vsize + prec;
                     70:   tp = (mp_ptr) TMP_ALLOC ((tsize + 1) * BYTES_PER_MP_LIMB);
                     71:
                     72:   if (usize > tsize)
                     73:     {
                     74:       up += usize - tsize;
                     75:       usize = tsize;
                     76:       rtp = tp;
                     77:     }
                     78:   else
                     79:     {
                     80:       MPN_ZERO (tp, tsize - usize);
                     81:       rtp = tp + (tsize - usize);
                     82:     }
                     83:
                     84:
                     85:   /* Normalize the divisor and the dividend.  */
1.1.1.3 ! ohara      86:   if ((vp[vsize-1] & GMP_NUMB_HIGHBIT) == 0)
1.1       maekawa    87:     {
                     88:       mp_ptr tmp;
                     89:       mp_limb_t nlimb;
1.1.1.3 ! ohara      90:       unsigned normalization_steps;
        !            91:
        !            92:       count_leading_zeros (normalization_steps, vp[vsize - 1]);
        !            93:       normalization_steps -= GMP_NAIL_BITS;
1.1       maekawa    94:
                     95:       /* Shift up the divisor setting the most significant bit of
                     96:         the most significant limb.  Use temporary storage not to clobber
                     97:         the original contents of the divisor.  */
                     98:       tmp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB);
                     99:       mpn_lshift (tmp, vp, vsize, normalization_steps);
                    100:       vp = tmp;
                    101:
                    102:       /* Shift up the dividend, possibly introducing a new most
                    103:         significant word.  Move the shifted dividend in the remainder
                    104:         at the same time.  */
                    105:       nlimb = mpn_lshift (rtp, up, usize, normalization_steps);
                    106:       if (nlimb != 0)
                    107:        {
                    108:          rtp[usize] = nlimb;
                    109:          tsize++;
                    110:          rexp++;
                    111:        }
                    112:     }
                    113:   else
                    114:     {
                    115:       /* The divisor is already normalized, as required.
                    116:         Copy it to temporary space if it overlaps with the quotient.  */
                    117:       if (vp - rp <= tsize - vsize)
                    118:        {
                    119:          mp_ptr tmp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB);
                    120:          MPN_COPY (tmp, vp, vsize);
                    121:          vp = (mp_srcptr) tmp;
                    122:        }
                    123:
                    124:       /* Move the dividend to the remainder.  */
                    125:       MPN_COPY (rtp, up, usize);
                    126:     }
                    127:
                    128:   q_limb = mpn_divmod (rp, tp, tsize, vp, vsize);
                    129:   rsize = tsize - vsize;
                    130:   if (q_limb)
                    131:     {
                    132:       rp[rsize] = q_limb;
                    133:       rsize++;
                    134:       rexp++;
                    135:     }
                    136:
                    137:   r->_mp_size = sign_quotient >= 0 ? rsize : -rsize;
                    138:   r->_mp_exp = rexp;
                    139:   TMP_FREE (marker);
                    140: }