Annotation of OpenXM_contrib/gmp/extract-dbl.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, 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: /* Extract a non-negative double in d. */
! 34:
! 35: int
! 36: #if __STDC__
! 37: __gmp_extract_double (mp_ptr rp, double d)
! 38: #else
! 39: __gmp_extract_double (rp, d)
! 40: mp_ptr rp;
! 41: double d;
! 42: #endif
! 43: {
! 44: long exp;
! 45: unsigned sc;
! 46: mp_limb_t manh, manl;
! 47:
! 48: /* BUGS
! 49:
! 50: 1. Should handle Inf and NaN in IEEE specific code.
! 51: 2. Handle Inf and NaN also in default code, to avoid hangs.
! 52: 3. Generalize to handle all BITS_PER_MP_LIMB >= 32.
! 53: 4. This lits is incomplete and misspelled.
! 54: */
! 55:
! 56: if (d == 0.0)
! 57: {
! 58: rp[0] = 0;
! 59: rp[1] = 0;
! 60: #if BITS_PER_MP_LIMB == 32
! 61: rp[2] = 0;
! 62: #endif
! 63: return 0;
! 64: }
! 65:
! 66: #if _GMP_IEEE_FLOATS
! 67: {
! 68: #if defined (__alpha) && __GNUC__ == 2 && __GNUC_MINOR__ == 8
! 69: /* Work around alpha-specific bug in GCC 2.8.x. */
! 70: volatile
! 71: #endif
! 72: union ieee_double_extract x;
! 73: x.d = d;
! 74: exp = x.s.exp;
! 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: if (exp == 0)
! 79: {
! 80: /* Denormalized number. Don't try to be clever about this,
! 81: since it is not an important case to make fast. */
! 82: exp = 1;
! 83: do
! 84: {
! 85: manl = manl << 1;
! 86: exp--;
! 87: }
! 88: while ((mp_limb_signed_t) manl >= 0);
! 89: }
! 90: #else
! 91: manh = ((mp_limb_t) 1 << 31) | (x.s.manh << 11) | (x.s.manl >> 21);
! 92: manl = x.s.manl << 11;
! 93: if (exp == 0)
! 94: {
! 95: /* Denormalized number. Don't try to be clever about this,
! 96: since it is not an important case to make fast. */
! 97: exp = 1;
! 98: do
! 99: {
! 100: manh = (manh << 1) | (manl >> 31);
! 101: manl = manl << 1;
! 102: exp--;
! 103: }
! 104: while ((mp_limb_signed_t) manh >= 0);
! 105: }
! 106: #endif
! 107: exp -= 1022; /* Remove IEEE bias. */
! 108: }
! 109: #else
! 110: {
! 111: /* Unknown (or known to be non-IEEE) double format. */
! 112: exp = 0;
! 113: if (d >= 1.0)
! 114: {
! 115: if (d * 0.5 == d)
! 116: abort ();
! 117:
! 118: while (d >= 32768.0)
! 119: {
! 120: d *= (1.0 / 65536.0);
! 121: exp += 16;
! 122: }
! 123: while (d >= 1.0)
! 124: {
! 125: d *= 0.5;
! 126: exp += 1;
! 127: }
! 128: }
! 129: else if (d < 0.5)
! 130: {
! 131: while (d < (1.0 / 65536.0))
! 132: {
! 133: d *= 65536.0;
! 134: exp -= 16;
! 135: }
! 136: while (d < 0.5)
! 137: {
! 138: d *= 2.0;
! 139: exp -= 1;
! 140: }
! 141: }
! 142:
! 143: d *= MP_BASE_AS_DOUBLE;
! 144: #if BITS_PER_MP_LIMB == 64
! 145: manl = d;
! 146: #else
! 147: manh = d;
! 148: manl = (d - manh) * MP_BASE_AS_DOUBLE;
! 149: #endif
! 150: }
! 151: #endif
! 152:
! 153: sc = (unsigned) exp % BITS_PER_MP_LIMB;
! 154:
! 155: /* We add something here to get rounding right. */
! 156: exp = (exp + 2048) / BITS_PER_MP_LIMB - 2048 / BITS_PER_MP_LIMB + 1;
! 157:
! 158: #if BITS_PER_MP_LIMB == 64
! 159: if (sc != 0)
! 160: {
! 161: rp[1] = manl >> (BITS_PER_MP_LIMB - sc);
! 162: rp[0] = manl << sc;
! 163: }
! 164: else
! 165: {
! 166: rp[1] = manl;
! 167: rp[0] = 0;
! 168: exp--;
! 169: }
! 170: #else
! 171: if (sc != 0)
! 172: {
! 173: rp[2] = manh >> (BITS_PER_MP_LIMB - sc);
! 174: rp[1] = (manl >> (BITS_PER_MP_LIMB - sc)) | (manh << sc);
! 175: rp[0] = manl << sc;
! 176: }
! 177: else
! 178: {
! 179: rp[2] = manh;
! 180: rp[1] = manl;
! 181: rp[0] = 0;
! 182: exp--;
! 183: }
! 184: #endif
! 185:
! 186: return exp;
! 187: }
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