+/* Split a double into fraction and mantissa.
+ Copyright (C) 2007 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2, or (at your option)
+ any later version.
+
+ This program 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 General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along
+ with this program; if not, write to the Free Software Foundation,
+ Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+
+#include <config.h>
+
+#if !(defined USE_LONG_DOUBLE && !HAVE_LONG_DOUBLE)
+
+/* Specification. */
+# include <math.h>
+
+# include <float.h>
+# ifdef USE_LONG_DOUBLE
+# include "isnanl-nolibm.h"
+# else
+# include "isnan.h"
+# endif
+
+/* This file assumes FLT_RADIX = 2. If FLT_RADIX is a power of 2 greater
+ than 2, or not even a power of 2, some rounding errors can occur, so that
+ then the returned mantissa is only guaranteed to be <= 1.0, not < 1.0. */
+
+# ifdef USE_LONG_DOUBLE
+# define FUNC frexpl
+# define DOUBLE long double
+# define ISNAN isnanl
+# define L_(literal) literal##L
+# else
+# define FUNC frexp
+# define DOUBLE double
+# define ISNAN isnan
+# define L_(literal) literal
+# endif
+
+DOUBLE
+FUNC (DOUBLE x, int *exp)
+{
+ int sign;
+ int exponent;
+
+ /* Test for NaN, infinity, and zero. */
+ if (ISNAN (x) || x + x == x)
+ {
+ *exp = 0;
+ return x;
+ }
+
+ sign = 0;
+ if (x < 0)
+ {
+ x = - x;
+ sign = -1;
+ }
+
+ if (0)
+ {
+ /* Implementation contributed by Paolo Bonzini.
+ Disabled because it's under GPL and doesn't pass the tests. */
+
+ /* Since the exponent is an 'int', it fits in 64 bits. Therefore the
+ loops are executed no more than 64 times. */
+ DOUBLE exponents[64];
+ DOUBLE *next;
+ int bit;
+
+ exponent = 0;
+ if (x >= L_(1.0))
+ {
+ for (next = exponents, exponents[0] = L_(2.0), bit = 1;
+ *next <= x + x;
+ bit <<= 1, next[1] = next[0] * next[0], next++);
+
+ for (; next >= exponents; bit >>= 1, next--)
+ if (x + x >= *next)
+ {
+ x /= *next;
+ exponent |= bit;
+ }
+ }
+ else if (x < L_(0.5))
+ {
+ for (next = exponents, exponents[0] = L_(0.5), bit = 1;
+ *next > x;
+ bit <<= 1, next[1] = next[0] * next[0], next++);
+
+ for (; next >= exponents; bit >>= 1, next--)
+ if (x < *next)
+ {
+ x /= *next;
+ exponent |= bit;
+ }
+ exponent = - exponent;
+ }
+ }
+ else
+ {
+ /* Implementation contributed by Bruno Haible. */
+
+ /* Since the exponent is an 'int', it fits in 64 bits. Therefore the
+ loops are executed no more than 64 times. */
+ DOUBLE pow2[64]; /* pow2[i] = 2^2^i */
+ DOUBLE powh[64]; /* powh[i] = 2^-2^i */
+ int i;
+
+ exponent = 0;
+ if (x >= L_(1.0))
+ {
+ /* A positive exponent. */
+ DOUBLE pow2_i; /* = pow2[i] */
+ DOUBLE powh_i; /* = powh[i] */
+
+ /* Invariants: pow2_i = 2^2^i, powh_i = 2^-2^i,
+ x * 2^exponent = argument, x >= 1.0. */
+ for (i = 0, pow2_i = L_(2.0), powh_i = L_(0.5);
+ ;
+ i++, pow2_i = pow2_i * pow2_i, powh_i = powh_i * powh_i)
+ {
+ if (x >= pow2_i)
+ {
+ exponent += (1 << i);
+ x *= powh_i;
+ }
+ else
+ break;
+
+ pow2[i] = pow2_i;
+ powh[i] = powh_i;
+ }
+ /* Avoid making x too small, as it could become a denormalized
+ number and thus lose precision. */
+ while (i > 0 && x < pow2[i - 1])
+ {
+ i--;
+ powh_i = powh[i];
+ }
+ exponent += (1 << i);
+ x *= powh_i;
+ /* Here 2^-2^i <= x < 1.0. */
+ }
+ else
+ {
+ /* A negative or zero exponent. */
+ DOUBLE pow2_i; /* = pow2[i] */
+ DOUBLE powh_i; /* = powh[i] */
+
+ /* Invariants: pow2_i = 2^2^i, powh_i = 2^-2^i,
+ x * 2^exponent = argument, x < 1.0. */
+ for (i = 0, pow2_i = L_(2.0), powh_i = L_(0.5);
+ ;
+ i++, pow2_i = pow2_i * pow2_i, powh_i = powh_i * powh_i)
+ {
+ if (x < powh_i)
+ {
+ exponent -= (1 << i);
+ x *= pow2_i;
+ }
+ else
+ break;
+
+ pow2[i] = pow2_i;
+ powh[i] = powh_i;
+ }
+ /* Here 2^-2^i <= x < 1.0. */
+ }
+
+ /* Invariants: x * 2^exponent = argument, and 2^-2^i <= x < 1.0. */
+ while (i > 0)
+ {
+ i--;
+ if (x < powh[i])
+ {
+ exponent -= (1 << i);
+ x *= pow2[i];
+ }
+ }
+ /* Here 0.5 <= x < 1.0. */
+ }
+
+ *exp = exponent;
+ return (sign < 0 ? - x : x);
+}
+
+#else
+
+/* This declaration is solely to ensure that after preprocessing
+ this file is never empty. */
+typedef int dummy;
+
+#endif