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Annotation of OpenXM_contrib/gmp/mpf/div.c, Revision 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: }