276 lines
6.3 KiB
C
276 lines
6.3 KiB
C
/* __gmp_extract_double -- convert from double to array of mp_limb_t.
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Copyright 1996, 1999, 2000, 2001, 2002, 2006 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#include "mpir.h"
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#include "gmp-impl.h"
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#ifdef XDEBUG
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#undef _GMP_IEEE_FLOATS
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#endif
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#ifndef _GMP_IEEE_FLOATS
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#define _GMP_IEEE_FLOATS 0
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#endif
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#define BITS_IN_MANTISSA 53
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/* Extract a non-negative double in d. */
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int
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__gmp_extract_double (mp_ptr rp, double d)
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{
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long exp;
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unsigned sc;
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#ifdef _LONG_LONG_LIMB
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#define BITS_PER_PART 64 /* somewhat bogus */
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unsigned long long int manl;
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#else
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#define BITS_PER_PART GMP_LIMB_BITS
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unsigned long int manh, manl;
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#endif
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/* BUGS
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1. Should handle Inf and NaN in IEEE specific code.
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2. Handle Inf and NaN also in default code, to avoid hangs.
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3. Generalize to handle all GMP_LIMB_BITS >= 32.
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4. This lits is incomplete and misspelled.
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*/
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ASSERT (d >= 0.0);
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if (d == 0.0)
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{
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MPN_ZERO (rp, LIMBS_PER_DOUBLE);
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return 0;
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}
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#if _GMP_IEEE_FLOATS
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{
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union ieee_double_extract x;
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x.d = d;
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exp = x.s.exp;
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#if BITS_PER_PART == 64 /* generalize this to BITS_PER_PART > BITS_IN_MANTISSA */
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manl = (((mp_limb_t) 1 << 63)
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| ((mp_limb_t) x.s.manh << 43) | ((mp_limb_t) x.s.manl << 11));
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if (exp == 0)
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{
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/* Denormalized number. Don't try to be clever about this,
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since it is not an important case to make fast. */
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exp = 1;
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do
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{
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manl = manl << 1;
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exp--;
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}
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while ((manl & GMP_LIMB_HIGHBIT) == 0);
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}
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#endif
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#if BITS_PER_PART == 32
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manh = ((mp_limb_t) 1 << 31) | (x.s.manh << 11) | (x.s.manl >> 21);
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manl = x.s.manl << 11;
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if (exp == 0)
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{
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/* Denormalized number. Don't try to be clever about this,
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since it is not an important case to make fast. */
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exp = 1;
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do
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{
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manh = (manh << 1) | (manl >> 31);
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manl = manl << 1;
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exp--;
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}
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while ((manh & GMP_LIMB_HIGHBIT) == 0);
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}
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#endif
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#if BITS_PER_PART != 32 && BITS_PER_PART != 64
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You need to generalize the code above to handle this.
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#endif
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exp -= 1022; /* Remove IEEE bias. */
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}
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#else
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{
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/* Unknown (or known to be non-IEEE) double format. */
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exp = 0;
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if (d >= 1.0)
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{
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ASSERT_ALWAYS (d * 0.5 != d);
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while (d >= 32768.0)
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{
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d *= (1.0 / 65536.0);
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exp += 16;
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}
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while (d >= 1.0)
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{
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d *= 0.5;
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exp += 1;
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}
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}
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else if (d < 0.5)
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{
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while (d < (1.0 / 65536.0))
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{
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d *= 65536.0;
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exp -= 16;
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}
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while (d < 0.5)
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{
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d *= 2.0;
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exp -= 1;
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}
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}
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d *= (4.0 * ((unsigned long int) 1 << (BITS_PER_PART - 2)));
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#if BITS_PER_PART == 64
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manl = d;
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#else
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manh = d;
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manl = (d - manh) * (4.0 * ((unsigned long int) 1 << (BITS_PER_PART - 2)));
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#endif
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}
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#endif /* IEEE */
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/* Up until here, we have ignored the actual limb size. Remains
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to split manh,,manl into an array of LIMBS_PER_DOUBLE limbs.
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*/
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sc = (unsigned) (exp + 64 * GMP_NUMB_BITS) % GMP_NUMB_BITS;
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/* We add something here to get rounding right. */
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exp = (exp + 64 * GMP_NUMB_BITS) / GMP_NUMB_BITS - 64 * GMP_NUMB_BITS / GMP_NUMB_BITS + 1;
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#if LIMBS_PER_DOUBLE == 2
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#if GMP_NAIL_BITS == 0
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if (sc != 0)
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{
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rp[1] = manl >> (GMP_LIMB_BITS - sc);
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rp[0] = manl << sc;
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}
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else
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{
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rp[1] = manl;
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rp[0] = 0;
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exp--;
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}
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#else
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if (sc > GMP_NAIL_BITS)
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{
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rp[1] = manl >> (GMP_LIMB_BITS - sc);
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rp[0] = (manl << (sc - GMP_NAIL_BITS)) & GMP_NUMB_MASK;
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}
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else
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{
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if (sc == 0)
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{
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rp[1] = manl >> GMP_NAIL_BITS;
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rp[0] = (manl << GMP_NUMB_BITS - GMP_NAIL_BITS) & GMP_NUMB_MASK;
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exp--;
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}
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else
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{
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rp[1] = manl >> (GMP_LIMB_BITS - sc);
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rp[0] = (manl >> (GMP_NAIL_BITS - sc)) & GMP_NUMB_MASK;
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}
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}
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#endif
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#endif
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#if LIMBS_PER_DOUBLE == 3
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#if GMP_NAIL_BITS == 0
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if (sc != 0)
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{
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rp[2] = manh >> (GMP_LIMB_BITS - sc);
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rp[1] = (manh << sc) | (manl >> (GMP_LIMB_BITS - sc));
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rp[0] = manl << sc;
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}
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else
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{
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rp[2] = manh;
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rp[1] = manl;
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rp[0] = 0;
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exp--;
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}
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#else
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if (sc > GMP_NAIL_BITS)
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{
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rp[2] = (manh >> (GMP_LIMB_BITS - sc));
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rp[1] = ((manh << (sc - GMP_NAIL_BITS)) |
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(manl >> (GMP_LIMB_BITS - sc + GMP_NAIL_BITS))) & GMP_NUMB_MASK;
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if (sc >= 2 * GMP_NAIL_BITS)
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rp[0] = (manl << sc - 2 * GMP_NAIL_BITS) & GMP_NUMB_MASK;
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else
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rp[0] = manl >> (2 * GMP_NAIL_BITS - sc) & GMP_NUMB_MASK;
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}
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else
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{
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if (sc == 0)
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{
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rp[2] = manh >> GMP_NAIL_BITS;
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rp[1] = ((manh << GMP_NUMB_BITS - GMP_NAIL_BITS) | (manl >> 2 * GMP_NAIL_BITS)) & GMP_NUMB_MASK;
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rp[0] = 0;
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exp--;
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}
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else
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{
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rp[2] = (manh >> (GMP_LIMB_BITS - sc));
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rp[1] = (manh >> (GMP_NAIL_BITS - sc)) & GMP_NUMB_MASK;
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rp[0] = ((manh << (GMP_NUMB_BITS - GMP_NAIL_BITS + sc))
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}
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}
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#endif
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#endif
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#if LIMBS_PER_DOUBLE > 3
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if (sc == 0)
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{
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int i;
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for (i = LIMBS_PER_DOUBLE - 1; i >= 0; i--)
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{
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rp[i] = manh >> (BITS_PER_ULONG - GMP_NUMB_BITS);
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manh = ((manh << GMP_NUMB_BITS)
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| (manl >> (BITS_PER_ULONG - GMP_NUMB_BITS)));
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manl = manl << GMP_NUMB_BITS;
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}
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exp--;
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}
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else
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{
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int i;
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rp[LIMBS_PER_DOUBLE - 1] = (manh >> (GMP_LIMB_BITS - sc));
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manh = (manh << sc) | (manl >> (GMP_LIMB_BITS - sc));
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manl = (manl << sc);
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for (i = LIMBS_PER_DOUBLE - 2; i >= 0; i--)
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{
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rp[i] = manh >> (BITS_PER_ULONG - GMP_NUMB_BITS);
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manh = ((manh << GMP_NUMB_BITS)
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| (manl >> (BITS_PER_ULONG - GMP_NUMB_BITS)));
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manl = manl << GMP_NUMB_BITS;
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}
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}
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#endif
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return exp;
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}
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