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Annotation of OpenXM_contrib/gmp/extract-double.c, Revision 1.1

1.1     ! maekawa     1: /* __gmp_extract_double -- convert from double to array of mp_limb_t.
        !             2:
        !             3: Copyright (C) 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:
        !            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: #define MP_BASE_AS_DOUBLE (2.0 * ((mp_limb_t) 1 << (BITS_PER_MP_LIMB - 1)))
        !            34:
        !            35: /* Extract a non-negative double in d.  */
        !            36:
        !            37: int
        !            38: #if __STDC__
        !            39: __gmp_extract_double (mp_ptr rp, double d)
        !            40: #else
        !            41: __gmp_extract_double (rp, d)
        !            42:      mp_ptr rp;
        !            43:      double d;
        !            44: #endif
        !            45: {
        !            46:   long exp;
        !            47:   unsigned sc;
        !            48:   mp_limb_t manh, manl;
        !            49:
        !            50:   /* BUGS
        !            51:
        !            52:      1. Should handle Inf and NaN in IEEE specific code.
        !            53:      2. Handle Inf and NaN also in default code, to avoid hangs.
        !            54:      3. Generalize to handle all BITS_PER_MP_LIMB >= 32.
        !            55:      4. This lits is incomplete and misspelled.
        !            56:    */
        !            57:
        !            58:   if (d == 0.0)
        !            59:     {
        !            60:       rp[0] = 0;
        !            61:       rp[1] = 0;
        !            62: #if BITS_PER_MP_LIMB == 32
        !            63:       rp[2] = 0;
        !            64: #endif
        !            65:       return 0;
        !            66:     }
        !            67:
        !            68: #if _GMP_IEEE_FLOATS
        !            69:   {
        !            70:     union ieee_double_extract x;
        !            71:     x.d = d;
        !            72:
        !            73:     exp = x.s.exp;
        !            74:     sc = (unsigned) (exp + 2) % BITS_PER_MP_LIMB;
        !            75: #if BITS_PER_MP_LIMB == 64
        !            76:     manl = (((mp_limb_t) 1 << 63)
        !            77:            | ((mp_limb_t) x.s.manh << 43) | ((mp_limb_t) x.s.manl << 11));
        !            78: #else
        !            79:     manh = ((mp_limb_t) 1 << 31) | (x.s.manh << 11) | (x.s.manl >> 21);
        !            80:     manl = x.s.manl << 11;
        !            81: #endif
        !            82:   }
        !            83: #else
        !            84:   {
        !            85:     /* Unknown (or known to be non-IEEE) double format.  */
        !            86:     exp = 0;
        !            87:     if (d >= 1.0)
        !            88:       {
        !            89:        if (d * 0.5 == d)
        !            90:          abort ();
        !            91:
        !            92:        while (d >= 32768.0)
        !            93:          {
        !            94:            d *= (1.0 / 65536.0);
        !            95:            exp += 16;
        !            96:          }
        !            97:        while (d >= 1.0)
        !            98:          {
        !            99:            d *= 0.5;
        !           100:            exp += 1;
        !           101:          }
        !           102:       }
        !           103:     else if (d < 0.5)
        !           104:       {
        !           105:        while (d < (1.0 / 65536.0))
        !           106:          {
        !           107:            d *=  65536.0;
        !           108:            exp -= 16;
        !           109:          }
        !           110:        while (d < 0.5)
        !           111:          {
        !           112:            d *= 2.0;
        !           113:            exp -= 1;
        !           114:          }
        !           115:       }
        !           116:
        !           117:     sc = (unsigned) exp % BITS_PER_MP_LIMB;
        !           118:
        !           119:     d *= MP_BASE_AS_DOUBLE;
        !           120: #if BITS_PER_MP_LIMB == 64
        !           121:     manl = d;
        !           122: #else
        !           123:     manh = d;
        !           124:     manl = (d - manh) * MP_BASE_AS_DOUBLE;
        !           125: #endif
        !           126:
        !           127:     exp += 1022;
        !           128:   }
        !           129: #endif
        !           130:
        !           131:   exp = (unsigned) (exp + 1) / BITS_PER_MP_LIMB - 1024 / BITS_PER_MP_LIMB + 1;
        !           132:
        !           133: #if BITS_PER_MP_LIMB == 64
        !           134:   if (sc != 0)
        !           135:     {
        !           136:       rp[1] = manl >> (BITS_PER_MP_LIMB - sc);
        !           137:       rp[0] = manl << sc;
        !           138:     }
        !           139:   else
        !           140:     {
        !           141:       rp[1] = manl;
        !           142:       rp[0] = 0;
        !           143:     }
        !           144: #else
        !           145:   if (sc != 0)
        !           146:     {
        !           147:       rp[2] = manh >> (BITS_PER_MP_LIMB - sc);
        !           148:       rp[1] = (manl >> (BITS_PER_MP_LIMB - sc)) | (manh << sc);
        !           149:       rp[0] = manl << sc;
        !           150:     }
        !           151:   else
        !           152:     {
        !           153:       rp[2] = manh;
        !           154:       rp[1] = manl;
        !           155:       rp[0] = 0;
        !           156:     }
        !           157: #endif
        !           158:
        !           159:   return exp;
        !           160: }