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authorNikos Mavrogiannopoulos <nmav@gnutls.org>2011-08-13 14:10:55 +0200
committerNikos Mavrogiannopoulos <nmav@gnutls.org>2011-08-13 14:15:05 +0200
commit2385c7f999c12802b11859a34b89ff7662b1f4af (patch)
treea6dc75e9438f5ea2413a627ce8dde5d28e2a195b /gl/frexp.c
parent7f373a9e760c1aaad40aff7878dba1399831c9c3 (diff)
downloadgnutls-2385c7f999c12802b11859a34b89ff7662b1f4af.tar.gz
Added crywrap to the distributed programs.
Diffstat (limited to 'gl/frexp.c')
-rw-r--r--gl/frexp.c166
1 files changed, 166 insertions, 0 deletions
diff --git a/gl/frexp.c b/gl/frexp.c
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+++ b/gl/frexp.c
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+/* Split a double into fraction and mantissa.
+ Copyright (C) 2007-2011 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 3 of the License, 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, see <http://www.gnu.org/licenses/>. */
+
+/* Written by Paolo Bonzini <bonzini@gnu.org>, 2003, and
+ Bruno Haible <bruno@clisp.org>, 2007. */
+
+#include <config.h>
+
+/* Specification. */
+#include <math.h>
+
+#include <float.h>
+#ifdef USE_LONG_DOUBLE
+# include "isnanl-nolibm.h"
+# include "fpucw.h"
+#else
+# include "isnand-nolibm.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 DECL_ROUNDING DECL_LONG_DOUBLE_ROUNDING
+# define BEGIN_ROUNDING() BEGIN_LONG_DOUBLE_ROUNDING ()
+# define END_ROUNDING() END_LONG_DOUBLE_ROUNDING ()
+# define L_(literal) literal##L
+#else
+# define FUNC frexp
+# define DOUBLE double
+# define ISNAN isnand
+# define DECL_ROUNDING
+# define BEGIN_ROUNDING()
+# define END_ROUNDING()
+# define L_(literal) literal
+#endif
+
+DOUBLE
+FUNC (DOUBLE x, int *expptr)
+{
+ int sign;
+ int exponent;
+ DECL_ROUNDING
+
+ /* Test for NaN, infinity, and zero. */
+ if (ISNAN (x) || x + x == x)
+ {
+ *expptr = 0;
+ return x;
+ }
+
+ sign = 0;
+ if (x < 0)
+ {
+ x = - x;
+ sign = -1;
+ }
+
+ BEGIN_ROUNDING ();
+
+ {
+ /* 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. */
+ }
+
+ if (sign < 0)
+ x = - x;
+
+ END_ROUNDING ();
+
+ *expptr = exponent;
+ return x;
+}