version 1.1.1.1, 2000/01/10 15:35:27 |
version 1.1.1.3, 2003/08/25 16:06:33 |
|
|
/* double mpz_get_d (mpz_t src) -- Return the double approximation to SRC. |
/* double mpz_get_d (mpz_t src) -- Return the double approximation to SRC. |
|
|
Copyright (C) 1996 Free Software Foundation, Inc. |
Copyright 1996, 1997, 2000, 2001, 2002 Free Software Foundation, Inc. |
|
|
This file is part of the GNU MP Library. |
This file is part of the GNU MP Library. |
|
|
The GNU MP Library is free software; you can redistribute it and/or modify |
The GNU MP Library is free software; you can redistribute it and/or modify |
it under the terms of the GNU Library General Public License as published by |
it under the terms of the GNU Lesser General Public License as published by |
the Free Software Foundation; either version 2 of the License, or (at your |
the Free Software Foundation; either version 2.1 of the License, or (at your |
option) any later version. |
option) any later version. |
|
|
The GNU MP Library is distributed in the hope that it will be useful, but |
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 |
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
License for more details. |
License for more details. |
|
|
You should have received a copy of the GNU Library General Public License |
You should have received a copy of the GNU Lesser General Public License |
along with the GNU MP Library; see the file COPYING.LIB. If not, write to |
along with the GNU MP Library; see the file COPYING.LIB. If not, write to |
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
MA 02111-1307, USA. */ |
MA 02111-1307, USA. */ |
|
|
#include "gmp.h" |
#include "gmp.h" |
#include "gmp-impl.h" |
#include "gmp-impl.h" |
|
#include "longlong.h" |
|
|
|
|
|
/* FIXME: Would prefer to inline this on all compilers, not just those with |
|
"inline". */ |
|
static inline int |
|
mpn_zero_p (mp_srcptr p, mp_size_t n) |
|
{ |
|
mp_size_t i; |
|
|
|
for (i = 0; i < n; i++) |
|
if (p[i] != 0) |
|
return 0; |
|
|
|
return 1; |
|
} |
|
|
|
|
double |
double |
#if __STDC__ |
|
mpz_get_d (mpz_srcptr src) |
mpz_get_d (mpz_srcptr src) |
#else |
|
mpz_get_d (src) |
|
mpz_srcptr src; |
|
#endif |
|
{ |
{ |
double res; |
double res; |
mp_size_t size, i, n_limbs_to_use; |
mp_size_t size; |
int negative; |
int negative; |
mp_ptr qp; |
mp_ptr qp; |
|
mp_limb_t hz, lz; |
|
int cnt; |
|
|
size = SIZ(src); |
size = SIZ(src); |
if (size == 0) |
if (size == 0) |
|
|
size = ABS (size); |
size = ABS (size); |
qp = PTR(src); |
qp = PTR(src); |
|
|
res = qp[size - 1]; |
if (size == 1) |
n_limbs_to_use = MIN (LIMBS_PER_DOUBLE, size); |
{ |
for (i = 2; i <= n_limbs_to_use; i++) |
res = qp[size - 1]; |
res = res * MP_BASE_AS_DOUBLE + qp[size - i]; |
} |
|
else if (size == 2) |
|
{ |
|
res = MP_BASE_AS_DOUBLE * qp[size - 1] + qp[size - 2]; |
|
} |
|
else |
|
{ |
|
count_leading_zeros (cnt, qp[size - 1]); |
|
cnt -= GMP_NAIL_BITS; |
|
|
res = __gmp_scale2 (res, (size - n_limbs_to_use) * BITS_PER_MP_LIMB); |
#if BITS_PER_MP_LIMB == 32 |
|
if (cnt == 0) |
|
{ |
|
hz = qp[size - 1]; |
|
lz = qp[size - 2]; |
|
} |
|
else |
|
{ |
|
hz = ((qp[size - 1] << cnt) | (qp[size - 2] >> GMP_NUMB_BITS - cnt)) & GMP_NUMB_MASK; |
|
lz = ((qp[size - 2] << cnt) | (qp[size - 3] >> GMP_NUMB_BITS - cnt)) & GMP_NUMB_MASK; |
|
} |
|
#if _GMP_IEEE_FLOATS |
|
/* Take bits from less significant limbs, but only if they may affect |
|
the result. */ |
|
if ((lz & 0x7ff) == 0x400) |
|
{ |
|
if (cnt != 0) |
|
lz += (((qp[size - 3] << cnt) & GMP_NUMB_MASK) != 0 |
|
|| ! mpn_zero_p (qp, size - 3)); |
|
else |
|
lz += (! mpn_zero_p (qp, size - 2)); |
|
} |
|
#endif |
|
res = MP_BASE_AS_DOUBLE * hz + lz; |
|
res = __gmp_scale2 (res, (size - 2) * GMP_NUMB_BITS - cnt); |
|
#endif |
|
#if BITS_PER_MP_LIMB == 64 |
|
if (cnt == 0) |
|
hz = qp[size - 1]; |
|
else |
|
hz = ((qp[size - 1] << cnt) | (qp[size - 2] >> GMP_NUMB_BITS - cnt)) & GMP_NUMB_MASK; |
|
#if _GMP_IEEE_FLOATS |
|
if ((hz & 0x7ff) == 0x400) |
|
{ |
|
if (cnt != 0) |
|
hz += (((qp[size - 2] << cnt) & GMP_NUMB_MASK) != 0 |
|
|| ! mpn_zero_p (qp, size - 2)); |
|
else |
|
hz += (! mpn_zero_p (qp, size - 1)); |
|
} |
|
#endif |
|
res = hz; |
|
res = __gmp_scale2 (res, (size - 1) * GMP_NUMB_BITS - cnt); |
|
#endif |
|
} |
|
|
return negative ? -res : res; |
return negative ? -res : res; |
} |
} |