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Annotation of OpenXM_contrib/gmp/insert-dbl.c, Revision 1.1

1.1     ! maekawa     1: /* __gmp_insert_double -- convert from array of mp_limb_t to double.
        !             2:
        !             3: Copyright (C) 1996, 1997, 1999, 2000 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 Lesser General Public License as published by
        !             9: the Free Software Foundation; either version 2.1 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 Lesser General Public
        !            15: License for more details.
        !            16:
        !            17: You should have received a copy of the GNU Lesser 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:
        !            25: #ifdef XDEBUG
        !            26: #undef _GMP_IEEE_FLOATS
        !            27: #endif
        !            28:
        !            29: #ifndef _GMP_IEEE_FLOATS
        !            30: #define _GMP_IEEE_FLOATS 0
        !            31: #endif
        !            32:
        !            33: double
        !            34: #if __STDC__
        !            35: __gmp_scale2 (double d, int exp)
        !            36: #else
        !            37: __gmp_scale2 (d, exp)
        !            38:      double d;
        !            39:      int exp;
        !            40: #endif
        !            41: {
        !            42: #if _GMP_IEEE_FLOATS
        !            43:   {
        !            44: #if defined (__alpha) && __GNUC__ == 2 && __GNUC_MINOR__ == 8
        !            45:     /* Work around alpha-specific bug in GCC 2.8.x.  */
        !            46:     volatile
        !            47: #endif
        !            48:     union ieee_double_extract x;
        !            49:     x.d = d;
        !            50:     exp += x.s.exp;
        !            51:     x.s.exp = exp;
        !            52:     if (exp >= 2047)
        !            53:       {
        !            54:        /* Return +-infinity */
        !            55:        x.s.exp = 2047;
        !            56:        x.s.manl = x.s.manh = 0;
        !            57:       }
        !            58:     else if (exp < 1)
        !            59:       {
        !            60:        x.s.exp = 1;            /* smallest exponent (biased) */
        !            61:        /* Divide result by 2 until we have scaled it to the right IEEE
        !            62:           denormalized number, but stop if it becomes zero.  */
        !            63:        while (exp < 1 && x.d != 0)
        !            64:          {
        !            65:            x.d *= 0.5;
        !            66:            exp++;
        !            67:          }
        !            68:       }
        !            69:     return x.d;
        !            70:   }
        !            71: #else
        !            72:   {
        !            73:     double factor, r;
        !            74:
        !            75:     factor = 2.0;
        !            76:     if (exp < 0)
        !            77:       {
        !            78:        factor = 0.5;
        !            79:        exp = -exp;
        !            80:       }
        !            81:     r = d;
        !            82:     if (exp != 0)
        !            83:       {
        !            84:        if ((exp & 1) != 0)
        !            85:          r *= factor;
        !            86:        exp >>= 1;
        !            87:        while (exp != 0)
        !            88:          {
        !            89:            factor *= factor;
        !            90:            if ((exp & 1) != 0)
        !            91:              r *= factor;
        !            92:            exp >>= 1;
        !            93:          }
        !            94:       }
        !            95:     return r;
        !            96:   }
        !            97: #endif
        !            98: }