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Annotation of OpenXM_contrib/gmp/mpf/ui_div.c, Revision 1.1

1.1     ! maekawa     1: /* mpf_ui_div -- Divide an unsigned integer with a float.
        !             2:
        !             3: Copyright (C) 1993, 1994, 1995, 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_ui_div (mpf_ptr r, unsigned long int u, mpf_srcptr v)
        !            29: #else
        !            30: mpf_ui_div (r, u, v)
        !            31:      mpf_ptr r;
        !            32:      unsigned long int u;
        !            33:      mpf_srcptr v;
        !            34: #endif
        !            35: {
        !            36:   mp_srcptr vp;
        !            37:   mp_ptr rp, tp;
        !            38:   mp_size_t 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:   vsize = v->_mp_size;
        !            48:   sign_quotient = vsize;
        !            49:   vsize = ABS (vsize);
        !            50:   prec = r->_mp_prec;
        !            51:
        !            52:   if (vsize == 0)
        !            53:     vsize = 1 / vsize;         /* divide by zero as directed */
        !            54:   if (u == 0)
        !            55:     {
        !            56:       r->_mp_size = 0;
        !            57:       r->_mp_exp = 0;
        !            58:       return;
        !            59:     }
        !            60:
        !            61:   TMP_MARK (marker);
        !            62:   rexp = 1 - v->_mp_exp;
        !            63:
        !            64:   rp = r->_mp_d;
        !            65:   vp = v->_mp_d;
        !            66:
        !            67:   if (vsize > prec)
        !            68:     {
        !            69:       vp += vsize - prec;
        !            70:       vsize = prec;
        !            71:     }
        !            72:
        !            73:   tsize = vsize + prec;
        !            74:   tp = (mp_ptr) TMP_ALLOC ((tsize + 1) * BYTES_PER_MP_LIMB);
        !            75:   MPN_ZERO (tp, tsize);
        !            76:
        !            77:   count_leading_zeros (normalization_steps, vp[vsize - 1]);
        !            78:
        !            79:   /* Normalize the divisor and the dividend.  */
        !            80:   if (normalization_steps != 0)
        !            81:     {
        !            82:       mp_ptr tmp;
        !            83:       mp_limb_t dividend_high, dividend_low;
        !            84:
        !            85:       /* Shift up the divisor setting the most significant bit of
        !            86:         the most significant limb.  Use temporary storage not to clobber
        !            87:         the original contents of the divisor.  */
        !            88:       tmp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB);
        !            89:       mpn_lshift (tmp, vp, vsize, normalization_steps);
        !            90:       vp = tmp;
        !            91:
        !            92:       /* Shift up the dividend, possibly introducing a new most
        !            93:         significant word.  */
        !            94:       dividend_high = (mp_limb_t) u >> (BITS_PER_MP_LIMB - normalization_steps);
        !            95:       dividend_low = (mp_limb_t) u << normalization_steps;
        !            96:
        !            97:       tp[tsize - 1] = dividend_low;
        !            98:       if (dividend_high != 0)
        !            99:        {
        !           100:          tp[tsize] = dividend_high;
        !           101:          tsize++;
        !           102:          rexp++;
        !           103:        }
        !           104:     }
        !           105:   else
        !           106:     {
        !           107:       /* The divisor is already normalized, as required.
        !           108:         Copy it to temporary space if it overlaps with the quotient.  */
        !           109:       if (vp - rp <= tsize - vsize)
        !           110:        {
        !           111:          mp_ptr tmp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB);
        !           112:          MPN_COPY (tmp, vp, vsize);
        !           113:          vp = (mp_srcptr) tmp;
        !           114:        }
        !           115:
        !           116:       tp[tsize - 1] = u;
        !           117:     }
        !           118:
        !           119:   q_limb = mpn_divmod (rp, tp, tsize, vp, vsize);
        !           120:   rsize = tsize - vsize;
        !           121:   if (q_limb)
        !           122:     {
        !           123:       rp[rsize] = q_limb;
        !           124:       rsize++;
        !           125:       rexp++;
        !           126:     }
        !           127:
        !           128:   r->_mp_size = sign_quotient >= 0 ? rsize : -rsize;
        !           129:   r->_mp_exp = rexp;
        !           130:   TMP_FREE (marker);
        !           131: }