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Annotation of OpenXM_contrib/gmp/mpf/div.c, Revision 1.1.1.1

1.1       maekawa     1: /* mpf_div -- Divide two floats.
                      2:
                      3: Copyright (C) 1993, 1994, 1996 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 Library General Public License as published by
                      9: the Free Software Foundation; either version 2 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 Library General Public
                     15: License for more details.
                     16:
                     17: You should have received a copy of the GNU Library 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: void
                     27: #if __STDC__
                     28: mpf_div (mpf_ptr r, mpf_srcptr u, mpf_srcptr v)
                     29: #else
                     30: mpf_div (r, u, v)
                     31:      mpf_ptr r;
                     32:      mpf_srcptr u;
                     33:      mpf_srcptr v;
                     34: #endif
                     35: {
                     36:   mp_srcptr up, vp;
                     37:   mp_ptr rp, tp, rtp;
                     38:   mp_size_t usize, vsize;
                     39:   mp_size_t rsize, tsize;
                     40:   mp_size_t sign_quotient;
                     41:   mp_size_t prec;
                     42:   unsigned normalization_steps;
                     43:   mp_limb_t q_limb;
                     44:   mp_exp_t rexp;
                     45:   TMP_DECL (marker);
                     46:
                     47:   usize = u->_mp_size;
                     48:   vsize = v->_mp_size;
                     49:   sign_quotient = usize ^ vsize;
                     50:   usize = ABS (usize);
                     51:   vsize = ABS (vsize);
                     52:   prec = r->_mp_prec;
                     53:
                     54:   if (vsize == 0)
                     55:     vsize = 1 / vsize;         /* divide by zero as directed */
                     56:   if (usize == 0)
                     57:     {
                     58:       r->_mp_size = 0;
                     59:       r->_mp_exp = 0;
                     60:       return;
                     61:     }
                     62:
                     63:   TMP_MARK (marker);
                     64:   rexp = u->_mp_exp - v->_mp_exp;
                     65:
                     66:   rp = r->_mp_d;
                     67:   up = u->_mp_d;
                     68:   vp = v->_mp_d;
                     69:
                     70:   if (vsize > prec)
                     71:     {
                     72:       vp += vsize - prec;
                     73:       vsize = prec;
                     74:     }
                     75:
                     76:   tsize = vsize + prec;
                     77:   tp = (mp_ptr) TMP_ALLOC ((tsize + 1) * BYTES_PER_MP_LIMB);
                     78:
                     79:   if (usize > tsize)
                     80:     {
                     81:       up += usize - tsize;
                     82:       usize = tsize;
                     83:       rtp = tp;
                     84:     }
                     85:   else
                     86:     {
                     87:       MPN_ZERO (tp, tsize - usize);
                     88:       rtp = tp + (tsize - usize);
                     89:     }
                     90:
                     91:   count_leading_zeros (normalization_steps, vp[vsize - 1]);
                     92:
                     93:   /* Normalize the divisor and the dividend.  */
                     94:   if (normalization_steps != 0)
                     95:     {
                     96:       mp_ptr tmp;
                     97:       mp_limb_t nlimb;
                     98:
                     99:       /* Shift up the divisor setting the most significant bit of
                    100:         the most significant limb.  Use temporary storage not to clobber
                    101:         the original contents of the divisor.  */
                    102:       tmp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB);
                    103:       mpn_lshift (tmp, vp, vsize, normalization_steps);
                    104:       vp = tmp;
                    105:
                    106:       /* Shift up the dividend, possibly introducing a new most
                    107:         significant word.  Move the shifted dividend in the remainder
                    108:         at the same time.  */
                    109:       nlimb = mpn_lshift (rtp, up, usize, normalization_steps);
                    110:       if (nlimb != 0)
                    111:        {
                    112:          rtp[usize] = nlimb;
                    113:          tsize++;
                    114:          rexp++;
                    115:        }
                    116:     }
                    117:   else
                    118:     {
                    119:       /* The divisor is already normalized, as required.
                    120:         Copy it to temporary space if it overlaps with the quotient.  */
                    121:       if (vp - rp <= tsize - vsize)
                    122:        {
                    123:          mp_ptr tmp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB);
                    124:          MPN_COPY (tmp, vp, vsize);
                    125:          vp = (mp_srcptr) tmp;
                    126:        }
                    127:
                    128:       /* Move the dividend to the remainder.  */
                    129:       MPN_COPY (rtp, up, usize);
                    130:     }
                    131:
                    132:   q_limb = mpn_divmod (rp, tp, tsize, vp, vsize);
                    133:   rsize = tsize - vsize;
                    134:   if (q_limb)
                    135:     {
                    136:       rp[rsize] = q_limb;
                    137:       rsize++;
                    138:       rexp++;
                    139:     }
                    140:
                    141:   r->_mp_size = sign_quotient >= 0 ? rsize : -rsize;
                    142:   r->_mp_exp = rexp;
                    143:   TMP_FREE (marker);
                    144: }