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Annotation of OpenXM_contrib/gmp/mpf/add.c, Revision 1.1.1.2

1.1       maekawa     1: /* mpf_add -- Add 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
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:
                     25: void
                     26: #if __STDC__
                     27: mpf_add (mpf_ptr r, mpf_srcptr u, mpf_srcptr v)
                     28: #else
                     29: mpf_add (r, u, v)
                     30:      mpf_ptr r;
                     31:      mpf_srcptr u;
                     32:      mpf_srcptr v;
                     33: #endif
                     34: {
                     35:   mp_srcptr up, vp;
                     36:   mp_ptr rp, tp;
                     37:   mp_size_t usize, vsize, rsize;
                     38:   mp_size_t prec;
                     39:   mp_exp_t uexp;
                     40:   mp_size_t ediff;
                     41:   mp_limb_t cy;
                     42:   int negate;
                     43:   TMP_DECL (marker);
                     44:
                     45:   usize = u->_mp_size;
                     46:   vsize = v->_mp_size;
                     47:
                     48:   /* Handle special cases that don't work in generic code below.  */
                     49:   if (usize == 0)
                     50:     {
                     51:       mpf_set (r, v);
                     52:       return;
                     53:     }
                     54:   if (vsize == 0)
                     55:     {
                     56:       mpf_set (r, u);
                     57:       return;
                     58:     }
                     59:
                     60:   /* If signs of U and V are different, perform subtraction.  */
                     61:   if ((usize ^ vsize) < 0)
                     62:     {
                     63:       __mpf_struct v_negated;
                     64:       v_negated._mp_size = -vsize;
                     65:       v_negated._mp_exp = v->_mp_exp;
                     66:       v_negated._mp_d = v->_mp_d;
                     67:       mpf_sub (r, u, &v_negated);
                     68:       return;
                     69:     }
                     70:
                     71:   TMP_MARK (marker);
                     72:
                     73:   /* Signs are now known to be the same.  */
                     74:   negate = usize < 0;
                     75:
                     76:   /* Make U be the operand with the largest exponent.  */
                     77:   if (u->_mp_exp < v->_mp_exp)
                     78:     {
                     79:       mpf_srcptr t;
                     80:       t = u; u = v; v = t;
                     81:       usize = u->_mp_size;
                     82:       vsize = v->_mp_size;
                     83:     }
                     84:
                     85:   usize = ABS (usize);
                     86:   vsize = ABS (vsize);
                     87:   up = u->_mp_d;
                     88:   vp = v->_mp_d;
                     89:   rp = r->_mp_d;
                     90:   prec = r->_mp_prec;
                     91:   uexp = u->_mp_exp;
                     92:   ediff = u->_mp_exp - v->_mp_exp;
                     93:
                     94:   /* If U extends beyond PREC, ignore the part that does.  */
                     95:   if (usize > prec)
                     96:     {
                     97:       up += usize - prec;
                     98:       usize = prec;
                     99:     }
                    100:
                    101:   /* If V extends beyond PREC, ignore the part that does.
                    102:      Note that this may make vsize negative.  */
                    103:   if (vsize + ediff > prec)
                    104:     {
                    105:       vp += vsize + ediff - prec;
                    106:       vsize = prec - ediff;
                    107:     }
                    108:
                    109: #if 0
                    110:   /* Locate the least significant non-zero limb in (the needed parts
                    111:      of) U and V, to simplify the code below.  */
                    112:   while (up[0] == 0)
                    113:     up++, usize--;
                    114:   while (vp[0] == 0)
                    115:     vp++, vsize--;
                    116: #endif
                    117:
                    118:   /* Allocate temp space for the result.  Allocate
                    119:      just vsize + ediff later???  */
                    120:   tp = (mp_ptr) TMP_ALLOC (prec * BYTES_PER_MP_LIMB);
                    121:
                    122:   if (ediff >= prec)
                    123:     {
                    124:       /* V completely cancelled.  */
                    125:       if (tp != up)
                    126:        MPN_COPY (rp, up, usize);
                    127:       rsize = usize;
                    128:     }
                    129:   else
                    130:     {
                    131:       /* uuuu     |  uuuu     |  uuuu     |  uuuu     |  uuuu    */
                    132:       /* vvvvvvv  |  vv       |    vvvvv  |    v      |       vv */
                    133:
                    134:       if (usize > ediff)
                    135:        {
                    136:          /* U and V partially overlaps.  */
                    137:          if (vsize + ediff <= usize)
                    138:            {
                    139:              /* uuuu     */
                    140:              /*   v      */
                    141:              mp_size_t size;
                    142:              size = usize - ediff - vsize;
                    143:              MPN_COPY (tp, up, size);
                    144:              cy = mpn_add (tp + size, up + size, usize - size, vp, vsize);
                    145:              rsize = usize;
                    146:            }
                    147:          else
                    148:            {
                    149:              /* uuuu     */
                    150:              /*   vvvvv  */
                    151:              mp_size_t size;
                    152:              size = vsize + ediff - usize;
                    153:              MPN_COPY (tp, vp, size);
                    154:              cy = mpn_add (tp + size, up, usize, vp + size, usize - ediff);
                    155:              rsize = vsize + ediff;
                    156:            }
                    157:        }
                    158:       else
                    159:        {
                    160:          /* uuuu     */
                    161:          /*      vv  */
                    162:          mp_size_t size;
                    163:          size = vsize + ediff - usize;
                    164:          MPN_COPY (tp, vp, vsize);
                    165:          MPN_ZERO (tp + vsize, ediff - usize);
                    166:          MPN_COPY (tp + size, up, usize);
                    167:          cy = 0;
                    168:          rsize = size + usize;
                    169:        }
                    170:
                    171:       MPN_COPY (rp, tp, rsize);
                    172:       rp[rsize] = cy;
                    173:       rsize += cy;
                    174:       uexp += cy;
                    175:     }
                    176:
                    177:   r->_mp_size = negate ? -rsize : rsize;
                    178:   r->_mp_exp = uexp;
                    179:   TMP_FREE (marker);
                    180: }