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-rw-r--r--lib/printf-frexp.c188
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diff --git a/lib/printf-frexp.c b/lib/printf-frexp.c
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+/* Split a double into fraction and mantissa, for hexadecimal printf.
+ 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 Lesser 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 Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#include <config.h>
+
+/* Specification. */
+#ifdef USE_LONG_DOUBLE
+# include "printf-frexpl.h"
+#else
+# include "printf-frexp.h"
+#endif
+
+#include <float.h>
+#include <math.h>
+#ifdef USE_LONG_DOUBLE
+# include "fpucw.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 <= 2.0, not < 2.0. */
+
+#ifdef USE_LONG_DOUBLE
+# define FUNC printf_frexpl
+# define DOUBLE long double
+# define MIN_EXP LDBL_MIN_EXP
+# if HAVE_FREXPL_IN_LIBC && HAVE_LDEXPL_IN_LIBC
+# define USE_FREXP_LDEXP
+# define FREXP frexpl
+# define LDEXP ldexpl
+# endif
+# 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 printf_frexp
+# define DOUBLE double
+# define MIN_EXP DBL_MIN_EXP
+# if HAVE_FREXP_IN_LIBC && HAVE_LDEXP_IN_LIBC
+# define USE_FREXP_LDEXP
+# define FREXP frexp
+# define LDEXP ldexp
+# endif
+# define DECL_ROUNDING
+# define BEGIN_ROUNDING()
+# define END_ROUNDING()
+# define L_(literal) literal
+#endif
+
+DOUBLE
+FUNC (DOUBLE x, int *expptr)
+{
+ int exponent;
+ DECL_ROUNDING
+
+ BEGIN_ROUNDING ();
+
+#ifdef USE_FREXP_LDEXP
+ /* frexp and ldexp are usually faster than the loop below. */
+ x = FREXP (x, &exponent);
+
+ x = x + x;
+ exponent -= 1;
+
+ if (exponent < MIN_EXP - 1)
+ {
+ x = LDEXP (x, exponent - (MIN_EXP - 1));
+ exponent = MIN_EXP - 1;
+ }
+#else
+ {
+ /* 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 nonnegative 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;
+ }
+ }
+ /* Here 1.0 <= x < 2^2^i. */
+ }
+ else
+ {
+ /* A negative 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, exponent >= MIN_EXP - 1. */
+ 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 (exponent - (1 << i) < MIN_EXP - 1)
+ break;
+
+ exponent -= (1 << i);
+ x *= pow2_i;
+ if (x >= L_(1.0))
+ break;
+
+ pow2[i] = pow2_i;
+ powh[i] = powh_i;
+ }
+ }
+ /* Here either x < 1.0 and exponent - 2^i < MIN_EXP - 1 <= exponent,
+ or 1.0 <= x < 2^2^i and exponent >= MIN_EXP - 1. */
+
+ if (x < L_(1.0))
+ /* Invariants: x * 2^exponent = argument, x < 1.0 and
+ exponent - 2^i < MIN_EXP - 1 <= exponent. */
+ while (i > 0)
+ {
+ i--;
+ if (exponent - (1 << i) >= MIN_EXP - 1)
+ {
+ exponent -= (1 << i);
+ x *= pow2[i];
+ if (x >= L_(1.0))
+ break;
+ }
+ }
+
+ /* Here either x < 1.0 and exponent = MIN_EXP - 1,
+ or 1.0 <= x < 2^2^i and exponent >= MIN_EXP - 1. */
+ }
+
+ /* Invariants: x * 2^exponent = argument, and
+ either x < 1.0 and exponent = MIN_EXP - 1,
+ or 1.0 <= x < 2^2^i and exponent >= MIN_EXP - 1. */
+ while (i > 0)
+ {
+ i--;
+ if (x >= pow2[i])
+ {
+ exponent += (1 << i);
+ x *= powh[i];
+ }
+ }
+ /* Here either x < 1.0 and exponent = MIN_EXP - 1,
+ or 1.0 <= x < 2.0 and exponent >= MIN_EXP - 1. */
+ }
+#endif
+
+ END_ROUNDING ();
+
+ *expptr = exponent;
+ return x;
+}