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Annotation of OpenXM_contrib/gmp/mpz/get_d.c, Revision 1.1.1.3

1.1       maekawa     1: /* double mpz_get_d (mpz_t src) -- Return the double approximation to SRC.
                      2:
1.1.1.3 ! ohara       3: Copyright 1996, 1997, 2000, 2001, 2002 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"
1.1.1.2   maekawa    24: #include "longlong.h"
                     25:
                     26:
1.1.1.3 ! ohara      27: /* FIXME: Would prefer to inline this on all compilers, not just those with
        !            28:    "inline".  */
        !            29: static inline int
        !            30: mpn_zero_p (mp_srcptr p, mp_size_t n)
1.1.1.2   maekawa    31: {
                     32:   mp_size_t i;
                     33:
                     34:   for (i = 0; i < n; i++)
1.1.1.3 ! ohara      35:     if (p[i] != 0)
        !            36:       return 0;
1.1.1.2   maekawa    37:
                     38:   return 1;
                     39: }
                     40:
1.1       maekawa    41:
                     42: double
                     43: mpz_get_d (mpz_srcptr src)
                     44: {
                     45:   double res;
1.1.1.2   maekawa    46:   mp_size_t size;
1.1       maekawa    47:   int negative;
                     48:   mp_ptr qp;
1.1.1.2   maekawa    49:   mp_limb_t hz, lz;
                     50:   int cnt;
1.1       maekawa    51:
                     52:   size = SIZ(src);
                     53:   if (size == 0)
                     54:     return 0.0;
                     55:
                     56:   negative = size < 0;
                     57:   size = ABS (size);
                     58:   qp = PTR(src);
                     59:
1.1.1.2   maekawa    60:   if (size == 1)
                     61:     {
                     62:       res = qp[size - 1];
                     63:     }
                     64:   else if (size == 2)
                     65:     {
                     66:       res = MP_BASE_AS_DOUBLE * qp[size - 1] + qp[size - 2];
                     67:     }
                     68:   else
                     69:     {
                     70:       count_leading_zeros (cnt, qp[size - 1]);
1.1.1.3 ! ohara      71:       cnt -= GMP_NAIL_BITS;
1.1.1.2   maekawa    72:
                     73: #if BITS_PER_MP_LIMB == 32
                     74:       if (cnt == 0)
                     75:        {
                     76:          hz = qp[size - 1];
                     77:          lz = qp[size - 2];
                     78:        }
                     79:       else
                     80:        {
1.1.1.3 ! ohara      81:          hz = ((qp[size - 1] << cnt) | (qp[size - 2] >> GMP_NUMB_BITS - cnt)) & GMP_NUMB_MASK;
        !            82:          lz = ((qp[size - 2] << cnt) | (qp[size - 3] >> GMP_NUMB_BITS - cnt)) & GMP_NUMB_MASK;
1.1.1.2   maekawa    83:        }
                     84: #if _GMP_IEEE_FLOATS
                     85:       /* Take bits from less significant limbs, but only if they may affect
                     86:         the result.  */
                     87:       if ((lz & 0x7ff) == 0x400)
                     88:        {
                     89:          if (cnt != 0)
1.1.1.3 ! ohara      90:            lz += (((qp[size - 3] << cnt) & GMP_NUMB_MASK) != 0
        !            91:                   || ! mpn_zero_p (qp, size - 3));
1.1.1.2   maekawa    92:          else
                     93:            lz += (! mpn_zero_p (qp, size - 2));
                     94:        }
                     95: #endif
                     96:       res = MP_BASE_AS_DOUBLE * hz + lz;
1.1.1.3 ! ohara      97:       res = __gmp_scale2 (res, (size - 2) * GMP_NUMB_BITS - cnt);
1.1.1.2   maekawa    98: #endif
                     99: #if BITS_PER_MP_LIMB == 64
                    100:       if (cnt == 0)
                    101:        hz = qp[size - 1];
                    102:       else
1.1.1.3 ! ohara     103:        hz = ((qp[size - 1] << cnt) | (qp[size - 2] >> GMP_NUMB_BITS - cnt)) & GMP_NUMB_MASK;
1.1.1.2   maekawa   104: #if _GMP_IEEE_FLOATS
                    105:       if ((hz & 0x7ff) == 0x400)
                    106:        {
                    107:          if (cnt != 0)
1.1.1.3 ! ohara     108:            hz += (((qp[size - 2] << cnt) & GMP_NUMB_MASK) != 0
        !           109:                   || ! mpn_zero_p (qp, size - 2));
1.1.1.2   maekawa   110:          else
                    111:            hz += (! mpn_zero_p (qp, size - 1));
                    112:        }
                    113: #endif
                    114:       res = hz;
1.1.1.3 ! ohara     115:       res = __gmp_scale2 (res, (size - 1) * GMP_NUMB_BITS - cnt);
1.1.1.2   maekawa   116: #endif
                    117:     }
1.1       maekawa   118:
                    119:   return negative ? -res : res;
                    120: }