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

1.1       maekawa     1: /* mpf_set_q (mpf_t rop, mpq_t op) -- Convert the rational op to the float rop.
                      2:
1.1.1.2 ! maekawa     3: Copyright (C) 1996, 1999 Free Software Foundation, Inc.
1.1       maekawa     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: #include "longlong.h"
                     25:
                     26: void
                     27: #if __STDC__
                     28: mpf_set_q (mpf_t r, mpq_srcptr q)
                     29: #else
                     30: mpf_set_q (r, q)
                     31:      mpf_t r;
                     32:      mpq_srcptr q;
                     33: #endif
                     34: {
                     35:   mp_ptr np, dp;
                     36:   mp_ptr rp;
                     37:   mp_size_t nsize, dsize;
                     38:   mp_size_t qsize, rsize;
                     39:   mp_size_t sign_quotient;
                     40:   unsigned normalization_steps;
                     41:   mp_limb_t qlimb;
                     42:   mp_ptr qp;
                     43:   mp_size_t prec;
                     44:   mp_exp_t exp;
                     45:   TMP_DECL (marker);
                     46:
                     47:   nsize = SIZ (&q->_mp_num);
                     48:   dsize = SIZ (&q->_mp_den);
                     49:
                     50:   if (nsize == 0)
                     51:     {
                     52:       SIZ (r) = 0;
                     53:       EXP (r) = 0;
                     54:       return;
                     55:     }
                     56:
                     57:   prec = PREC (r) + 1;
                     58:
                     59:   TMP_MARK (marker);
                     60:
                     61:   qp = PTR (r);
                     62:
                     63:   sign_quotient = nsize ^ dsize;
                     64:   nsize = ABS (nsize);
                     65:   dsize = ABS (dsize);
                     66:   np = PTR (&q->_mp_num);
                     67:   dp = PTR (&q->_mp_den);
                     68:
                     69:   exp = nsize - dsize;
                     70:
                     71:   if (nsize > prec)
                     72:     {
                     73:       np += nsize - prec;
                     74:       nsize = prec;
                     75:     }
                     76:   if (dsize > prec)
                     77:     {
                     78:       dp += dsize - prec;
                     79:       dsize = prec;
                     80:     }
                     81:
                     82:   rsize = MAX (nsize, dsize);
                     83:   rp = (mp_ptr) TMP_ALLOC ((rsize + 1) * BYTES_PER_MP_LIMB);
                     84:
                     85:   count_leading_zeros (normalization_steps, dp[dsize - 1]);
                     86:
                     87:   /* Normalize the denominator, i.e. make its most significant bit set by
                     88:      shifting it NORMALIZATION_STEPS bits to the left.  Also shift the
                     89:      numerator the same number of steps (to keep the quotient the same!).  */
                     90:   if (normalization_steps != 0)
                     91:     {
                     92:       mp_ptr tp;
                     93:       mp_limb_t nlimb;
                     94:
                     95:       /* Shift up the denominator setting the most significant bit of
                     96:         the most significant limb.  Use temporary storage not to clobber
                     97:         the original contents of the denominator.  */
                     98:       tp = (mp_ptr) TMP_ALLOC (dsize * BYTES_PER_MP_LIMB);
                     99:       mpn_lshift (tp, dp, dsize, normalization_steps);
                    100:       dp = tp;
                    101:
                    102:       if (rsize != nsize)
                    103:        {
                    104:          MPN_ZERO (rp, rsize - nsize);
                    105:          nlimb = mpn_lshift (rp + (rsize - nsize),
                    106:                              np, nsize, normalization_steps);
                    107:        }
                    108:       else
                    109:        {
1.1.1.2 ! maekawa   110:          nlimb = mpn_lshift (rp, np, rsize, normalization_steps);
1.1       maekawa   111:        }
                    112:       if (nlimb != 0)
                    113:        {
                    114:          rp[rsize] = nlimb;
                    115:          exp++;
1.1.1.2 ! maekawa   116:          /* Don't just increase rsize, chop off rp at the low end instead.  */
        !           117:          if (rsize == prec)
        !           118:            rp++;
        !           119:          else
        !           120:            rsize++;
1.1       maekawa   121:        }
                    122:     }
                    123:   else
                    124:     {
                    125:       if (rsize != nsize)
                    126:        {
                    127:          MPN_ZERO (rp, rsize - nsize);
                    128:          MPN_COPY (rp + (rsize - nsize), np, nsize);
                    129:        }
                    130:       else
                    131:        {
                    132:          MPN_COPY (rp, np, rsize);
                    133:        }
                    134:     }
                    135:
                    136:   qlimb = mpn_divrem (qp, prec - 1 - (rsize - dsize), rp, rsize, dp, dsize);
                    137:   qsize = prec - 1;
                    138:   if (qlimb)
                    139:     {
                    140:       qp[qsize] = qlimb;
                    141:       qsize++;
                    142:       exp++;
                    143:     }
                    144:
                    145:   EXP (r) = exp;
1.1.1.2 ! maekawa   146:   SIZ (r) = sign_quotient >= 0 ? qsize : -qsize;
1.1       maekawa   147:
                    148:   TMP_FREE (marker);
                    149: }