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

1.1       maekawa     1: /* mpf_ui_div -- Divide an unsigned integer with a float.
                      2:
1.1.1.3 ! ohara       3: Copyright 1993, 1994, 1995, 1996, 2000, 2001, 2002 Free Software Foundation,
        !             4: Inc.
1.1       maekawa     5:
                      6: This file is part of the GNU MP Library.
                      7:
                      8: The GNU MP Library is free software; you can redistribute it and/or modify
1.1.1.2   maekawa     9: it under the terms of the GNU Lesser General Public License as published by
                     10: the Free Software Foundation; either version 2.1 of the License, or (at your
1.1       maekawa    11: option) any later version.
                     12:
                     13: The GNU MP Library is distributed in the hope that it will be useful, but
                     14: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
1.1.1.2   maekawa    15: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
1.1       maekawa    16: License for more details.
                     17:
1.1.1.2   maekawa    18: You should have received a copy of the GNU Lesser General Public License
1.1       maekawa    19: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     20: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     21: MA 02111-1307, USA. */
                     22:
                     23: #include "gmp.h"
                     24: #include "gmp-impl.h"
                     25: #include "longlong.h"
                     26:
                     27: void
                     28: mpf_ui_div (mpf_ptr r, unsigned long int u, mpf_srcptr v)
                     29: {
                     30:   mp_srcptr vp;
                     31:   mp_ptr rp, tp;
                     32:   mp_size_t vsize;
                     33:   mp_size_t rsize, tsize;
                     34:   mp_size_t sign_quotient;
                     35:   mp_size_t prec;
                     36:   mp_limb_t q_limb;
                     37:   mp_exp_t rexp;
                     38:   TMP_DECL (marker);
                     39:
                     40:   vsize = v->_mp_size;
                     41:   sign_quotient = vsize;
                     42:   vsize = ABS (vsize);
                     43:   prec = r->_mp_prec;
                     44:
                     45:   if (vsize == 0)
1.1.1.2   maekawa    46:     DIVIDE_BY_ZERO;
                     47:
1.1       maekawa    48:   if (u == 0)
                     49:     {
                     50:       r->_mp_size = 0;
                     51:       r->_mp_exp = 0;
                     52:       return;
                     53:     }
                     54:
                     55:   TMP_MARK (marker);
                     56:   rexp = 1 - v->_mp_exp;
                     57:
                     58:   rp = r->_mp_d;
                     59:   vp = v->_mp_d;
                     60:
                     61:   if (vsize > prec)
                     62:     {
                     63:       vp += vsize - prec;
                     64:       vsize = prec;
                     65:     }
                     66:
                     67:   tsize = vsize + prec;
                     68:   tp = (mp_ptr) TMP_ALLOC ((tsize + 1) * BYTES_PER_MP_LIMB);
                     69:   MPN_ZERO (tp, tsize);
                     70:
                     71:   /* Normalize the divisor and the dividend.  */
1.1.1.3 ! ohara      72:   if ((vp[vsize - 1] & GMP_NUMB_HIGHBIT) == 0)
1.1       maekawa    73:     {
                     74:       mp_ptr tmp;
                     75:       mp_limb_t dividend_high, dividend_low;
1.1.1.3 ! ohara      76:       unsigned normalization_steps;
        !            77:
        !            78:       count_leading_zeros (normalization_steps, vp[vsize - 1]);
        !            79:       normalization_steps -= GMP_NAIL_BITS;
1.1       maekawa    80:
                     81:       /* Shift up the divisor setting the most significant bit of
                     82:         the most significant limb.  Use temporary storage not to clobber
                     83:         the original contents of the divisor.  */
                     84:       tmp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB);
                     85:       mpn_lshift (tmp, vp, vsize, normalization_steps);
                     86:       vp = tmp;
                     87:
                     88:       /* Shift up the dividend, possibly introducing a new most
                     89:         significant word.  */
1.1.1.3 ! ohara      90:       dividend_high = (mp_limb_t) u >> (GMP_NUMB_BITS - normalization_steps);
        !            91:       dividend_low = ((mp_limb_t) u << normalization_steps) & GMP_NUMB_MASK;
1.1       maekawa    92:
                     93:       tp[tsize - 1] = dividend_low;
                     94:       if (dividend_high != 0)
                     95:        {
1.1.1.3 ! ohara      96: #if GMP_NAIL_BITS != 0
        !            97:          if (dividend_high > vp[vsize - 1])
        !            98:            {
        !            99:              tp[tsize - 2] = dividend_low;
        !           100:              tp[tsize - 1] = dividend_high & GMP_NUMB_MASK;
        !           101:              tp[tsize] = dividend_high >> GMP_NUMB_BITS;
        !           102:              tsize++;
        !           103:              rexp += 2;
        !           104:            }
        !           105:          else
        !           106: #endif
        !           107:            {
        !           108:              tp[tsize] = dividend_high;
        !           109:              tsize++;
        !           110:              rexp++;
        !           111:            }
1.1       maekawa   112:        }
                    113:     }
                    114:   else
                    115:     {
                    116:       /* The divisor is already normalized, as required.
                    117:         Copy it to temporary space if it overlaps with the quotient.  */
                    118:       if (vp - rp <= tsize - vsize)
                    119:        {
                    120:          mp_ptr tmp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB);
                    121:          MPN_COPY (tmp, vp, vsize);
                    122:          vp = (mp_srcptr) tmp;
                    123:        }
                    124:
1.1.1.3 ! ohara     125:       tp[tsize - 1] = u & GMP_NUMB_MASK;
        !           126: #if GMP_NAIL_BITS != 0
        !           127:       if (u > GMP_NUMB_MAX)
        !           128:        {
        !           129:          tp[tsize] = u >> GMP_NUMB_BITS;
        !           130:          tsize++;
        !           131:          rexp++;
        !           132:        }
        !           133: #endif
1.1       maekawa   134:     }
                    135:
                    136:   q_limb = mpn_divmod (rp, tp, tsize, vp, vsize);
                    137:   rsize = tsize - vsize;
                    138:   if (q_limb)
                    139:     {
                    140:       rp[rsize] = q_limb;
                    141:       rsize++;
                    142:       rexp++;
                    143:     }
                    144:
                    145:   r->_mp_size = sign_quotient >= 0 ? rsize : -rsize;
                    146:   r->_mp_exp = rexp;
                    147:   TMP_FREE (marker);
                    148: }