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/* mpfr_set_ld -- convert a machine long double to
a multiple precision floating-point number
Copyright 2002, 2003 Free Software Foundation, Inc.
This file is part of the MPFR Library.
The MPFR 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 2.1 of the License, or (at your
option) any later version.
The MPFR 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 MPFR Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include <float.h>
#include <limits.h> /* for CHAR_BIT */
#include "gmp.h"
#include "gmp-impl.h"
#include "mpfr.h"
#include "mpfr-impl.h"
#ifndef DBL_MANT_DIG
#define DBL_MANT_DIG 53
#endif
#ifndef CHAR_BIT
#define CHAR_BIT 8
#endif
/* Various i386 systems have been seen with float.h LDBL constants equal to
the DBL ones, whereas they ought to be bigger, reflecting the 10-byte
IEEE extended format on that processor. gcc 3.2.1 on FreeBSD and Solaris
has been seen with the problem, and gcc 2.95.4 on FreeBSD 4.7. */
#if HAVE_LDOUBLE_IEEE_EXT_LITTLE
static const struct {
char bytes[10];
long double dummy; /* for memory alignment */
} ldbl_max_struct = {
{ '\xFF','\xFF','\xFF','\xFF',
'\xFF','\xFF','\xFF','\xFF',
'\xFE','\x7F' }
};
#define MPFR_LDBL_MAX (* (const long double *) ldbl_max_struct.bytes)
#else
#define MPFR_LDBL_MAX LDBL_MAX
#endif
/* This is an overestimate, but fine for our purposes, it only needs to be
enough that "t" below can hold a long double without rounding. */
#define MPFR_LDBL_MANT_DIG (CHAR_BIT * sizeof (long double))
int
mpfr_set_ld (mpfr_ptr r, long double d, mp_rnd_t rnd_mode)
{
mpfr_t t, u;
int inexact, shift_exp = 0, inexact2 = 0;
LONGDOUBLE_NAN_ACTION (d, goto nan);
if (d > MPFR_LDBL_MAX)
{
mpfr_set_inf (r, 1);
return 0;
}
if (d < -MPFR_LDBL_MAX)
{
mpfr_set_inf (r, -1);
return 0;
}
if (d == 0.0)
return mpfr_set_d (r, (double) d, rnd_mode);
mpfr_init2 (t, MPFR_LDBL_MANT_DIG);
mpfr_init2 (u, DBL_MANT_DIG);
mpfr_set_ui (t, 0, GMP_RNDN);
while (d != 0.0)
{
if ((d > (long double) DBL_MAX) || ((-d) > (long double) DBL_MAX))
{ /* d is neither +Inf nor -Inf and u is Inf: this implies that an
overflow occured, i.e. the exponent of d is too large for the
double format */
long double div9, div10, div11, div12, div13;
div9 = (long double) (double) 1.34078079299425971e154; /* 2^(2^9) */
div10 = div9 * div9;
div11 = div10 * div10; /* 2^(2^11) */
div12 = div11 * div11; /* 2^(2^12) */
div13 = div12 * div12; /* 2^(2^13) */
if (ABS(d) >= div13)
{
d = d / div13; /* exact */
shift_exp += 8192;
}
if (ABS(d) >= div12)
{
d = d / div12; /* exact */
shift_exp += 4096;
}
if (ABS(d) >= div11)
{
d = d / div11; /* exact */
shift_exp += 2048;
}
if (ABS(d) >= div10)
{
d = d / div10; /* exact */
shift_exp += 1024;
}
/* warning: we may have DBL_MAX=2^1024*(1-2^(-53)) < d < 2^1024,
therefore we have one extra exponent reduction step */
if (ABS(d) >= div9)
{
d = d / div9; /* exact */
shift_exp += 512;
}
mpfr_set_ui (u, 0, GMP_RNDZ);
}
else
{
/* since -DBL_MAX <= d <= DBL_MAX, the cast to double should not
overflow here */
mpfr_set_d (u, (double) d, GMP_RNDN);
/* warning: using MPFR_IS_ZERO will cause a READ_UNINIT_MEM if u=Inf */
if (mpfr_cmp_ui (u, 0) == 0 && (d != (long double) 0.0)) /* underflow */
{
long double div10, div11, div12, div13;
div10 = (long double) (double) 5.5626846462680034577255e-309; /* 2^(-2^10) */
div11 = div10 * div10; /* 2^(-2^11) */
div12 = div11 * div11; /* 2^(-2^12) */
div13 = div12 * div12; /* 2^(-2^13) */
if (ABS(d) <= div13)
{
d = d / div13; /* exact */
shift_exp -= 8192;
}
if (ABS(d) <= div12)
{
d = d / div12; /* exact */
shift_exp -= 4096;
}
if (ABS(d) <= div11)
{
d = d / div11; /* exact */
shift_exp -= 2048;
}
if (ABS(d) <= div10)
{
d = d / div10; /* exact */
shift_exp -= 1024;
}
}
}
mpfr_add (t, t, u, GMP_RNDN); /* exact */
if (!mpfr_number_p (t))
break;
d = d - (long double) mpfr_get_d1 (u); /* exact */
}
/* now t is exactly the input value d */
inexact = mpfr_set (r, t, rnd_mode);
if (shift_exp > 0)
inexact2 = mpfr_mul_2exp (r, r, shift_exp, rnd_mode);
else if (shift_exp < 0)
inexact2 = mpfr_div_2exp (r, r, -shift_exp, rnd_mode);
if (inexact2) /* overflow */
inexact = inexact2;
mpfr_clear (t);
mpfr_clear (u);
return inexact;
nan:
MPFR_SET_NAN(r);
MPFR_RET_NAN;
}
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