/* __gmp_extract_double -- convert from double to array of mp_limb_t.
Copyright 1996, 1999, 2000, 2001, 2002, 2006 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at your
option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
#include "gmp.h"
#include "gmp-impl.h"
#ifdef XDEBUG
#undef _GMP_IEEE_FLOATS
#endif
#ifndef _GMP_IEEE_FLOATS
#define _GMP_IEEE_FLOATS 0
#endif
#define BITS_IN_MANTISSA 53
/* Extract a non-negative double in d. */
int
__gmp_extract_double (mp_ptr rp, double d)
{
long exp;
unsigned sc;
#ifdef _LONG_LONG_LIMB
#define BITS_PER_PART 64 /* somewhat bogus */
unsigned long long int manl;
#else
#define BITS_PER_PART GMP_LIMB_BITS
unsigned long int manh, manl;
#endif
/* BUGS
1. Should handle Inf and NaN in IEEE specific code.
2. Handle Inf and NaN also in default code, to avoid hangs.
3. Generalize to handle all GMP_LIMB_BITS >= 32.
4. This lits is incomplete and misspelled.
*/
ASSERT (d >= 0.0);
if (d == 0.0)
{
MPN_ZERO (rp, LIMBS_PER_DOUBLE);
return 0;
}
#if _GMP_IEEE_FLOATS
{
#if defined (__alpha) && __GNUC__ == 2 && __GNUC_MINOR__ == 8
/* Work around alpha-specific bug in GCC 2.8.x. */
volatile
#endif
union ieee_double_extract x;
x.d = d;
exp = x.s.exp;
#if BITS_PER_PART == 64 /* generalize this to BITS_PER_PART > BITS_IN_MANTISSA */
manl = (((mp_limb_t) 1 << 63)
| ((mp_limb_t) x.s.manh << 43) | ((mp_limb_t) x.s.manl << 11));
if (exp == 0)
{
/* Denormalized number. Don't try to be clever about this,
since it is not an important case to make fast. */
exp = 1;
do
{
manl = manl << 1;
exp--;
}
while ((manl & GMP_LIMB_HIGHBIT) == 0);
}
#endif
#if BITS_PER_PART == 32
manh = ((mp_limb_t) 1 << 31) | (x.s.manh << 11) | (x.s.manl >> 21);
manl = x.s.manl << 11;
if (exp == 0)
{
/* Denormalized number. Don't try to be clever about this,
since it is not an important case to make fast. */
exp = 1;
do
{
manh = (manh << 1) | (manl >> 31);
manl = manl << 1;
exp--;
}
while ((manh & GMP_LIMB_HIGHBIT) == 0);
}
#endif
#if BITS_PER_PART != 32 && BITS_PER_PART != 64
You need to generalize the code above to handle this.
#endif
exp -= 1022; /* Remove IEEE bias. */
}
#else
{
/* Unknown (or known to be non-IEEE) double format. */
exp = 0;
if (d >= 1.0)
{
ASSERT_ALWAYS (d * 0.5 != d);
while (d >= 32768.0)
{
d *= (1.0 / 65536.0);
exp += 16;
}
while (d >= 1.0)
{
d *= 0.5;
exp += 1;
}
}
else if (d < 0.5)
{
while (d < (1.0 / 65536.0))
{
d *= 65536.0;
exp -= 16;
}
while (d < 0.5)
{
d *= 2.0;
exp -= 1;
}
}
d *= (4.0 * ((unsigned long int) 1 << (BITS_PER_PART - 2)));
#if BITS_PER_PART == 64
manl = d;
#else
manh = d;
manl = (d - manh) * (4.0 * ((unsigned long int) 1 << (BITS_PER_PART - 2)));
#endif
}
#endif /* IEEE */
/* Up until here, we have ignored the actual limb size. Remains
to split manh,,manl into an array of LIMBS_PER_DOUBLE limbs.
*/
sc = (unsigned) (exp + 64 * GMP_NUMB_BITS) % GMP_NUMB_BITS;
/* We add something here to get rounding right. */
exp = (exp + 64 * GMP_NUMB_BITS) / GMP_NUMB_BITS - 64 * GMP_NUMB_BITS / GMP_NUMB_BITS + 1;
#if LIMBS_PER_DOUBLE == 2
#if GMP_NAIL_BITS == 0
if (sc != 0)
{
rp[1] = manl >> (GMP_LIMB_BITS - sc);
rp[0] = manl << sc;
}
else
{
rp[1] = manl;
rp[0] = 0;
exp--;
}
#else
if (sc > GMP_NAIL_BITS)
{
rp[1] = manl >> (GMP_LIMB_BITS - sc);
rp[0] = (manl << (sc - GMP_NAIL_BITS)) & GMP_NUMB_MASK;
}
else
{
if (sc == 0)
{
rp[1] = manl >> GMP_NAIL_BITS;
rp[0] = (manl << GMP_NUMB_BITS - GMP_NAIL_BITS) & GMP_NUMB_MASK;
exp--;
}
else
{
rp[1] = manl >> (GMP_LIMB_BITS - sc);
rp[0] = (manl >> (GMP_NAIL_BITS - sc)) & GMP_NUMB_MASK;
}
}
#endif
#endif
#if LIMBS_PER_DOUBLE == 3
#if GMP_NAIL_BITS == 0
if (sc != 0)
{
rp[2] = manh >> (GMP_LIMB_BITS - sc);
rp[1] = (manh << sc) | (manl >> (GMP_LIMB_BITS - sc));
rp[0] = manl << sc;
}
else
{
rp[2] = manh;
rp[1] = manl;
rp[0] = 0;
exp--;
}
#else
if (sc > GMP_NAIL_BITS)
{
rp[2] = (manh >> (GMP_LIMB_BITS - sc));
rp[1] = ((manh << (sc - GMP_NAIL_BITS)) |
(manl >> (GMP_LIMB_BITS - sc + GMP_NAIL_BITS))) & GMP_NUMB_MASK;
if (sc >= 2 * GMP_NAIL_BITS)
rp[0] = (manl << sc - 2 * GMP_NAIL_BITS) & GMP_NUMB_MASK;
else
rp[0] = manl >> (2 * GMP_NAIL_BITS - sc) & GMP_NUMB_MASK;
}
else
{
if (sc == 0)
{
rp[2] = manh >> GMP_NAIL_BITS;
rp[1] = ((manh << GMP_NUMB_BITS - GMP_NAIL_BITS) | (manl >> 2 * GMP_NAIL_BITS)) & GMP_NUMB_MASK;
rp[0] = 0;
exp--;
}
else
{
rp[2] = (manh >> (GMP_LIMB_BITS - sc));
rp[1] = (manh >> (GMP_NAIL_BITS - sc)) & GMP_NUMB_MASK;
rp[0] = ((manh << (GMP_NUMB_BITS - GMP_NAIL_BITS + sc))
| (manl >> (GMP_LIMB_BITS - (GMP_NUMB_BITS - GMP_NAIL_BITS + sc)))) & GMP_NUMB_MASK;
}
}
#endif
#endif
#if LIMBS_PER_DOUBLE > 3
if (sc == 0)
{
int i;
for (i = LIMBS_PER_DOUBLE - 1; i >= 0; i--)
{
rp[i] = manh >> (BITS_PER_ULONG - GMP_NUMB_BITS);
manh = ((manh << GMP_NUMB_BITS)
| (manl >> (BITS_PER_ULONG - GMP_NUMB_BITS)));
manl = manl << GMP_NUMB_BITS;
}
exp--;
}
else
{
int i;
rp[LIMBS_PER_DOUBLE - 1] = (manh >> (GMP_LIMB_BITS - sc));
manh = (manh << sc) | (manl >> (GMP_LIMB_BITS - sc));
manl = (manl << sc);
for (i = LIMBS_PER_DOUBLE - 2; i >= 0; i--)
{
rp[i] = manh >> (BITS_PER_ULONG - GMP_NUMB_BITS);
manh = ((manh << GMP_NUMB_BITS)
| (manl >> (BITS_PER_ULONG - GMP_NUMB_BITS)));
manl = manl << GMP_NUMB_BITS;
}
}
#endif
return exp;
}
syntax highlighted by Code2HTML, v. 0.9.1