Imported Upstream version 93u+upstream

1 files changed, 153 insertions, 0 deletions

diff --git a/src/lib/libast/comp/frexp.c b/src/lib/libast/comp/frexp.c
new file mode 100644
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+++ b/src/lib/libast/comp/frexp.c
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+/***********************************************************************
+*                                                                      *
+*               This software is part of the ast package               *
+*          Copyright (c) 1985-2011 AT&T Intellectual Property          *
+*                      and is licensed under the                       *
+*                 Eclipse Public License, Version 1.0                  *
+*                    by AT&T Intellectual Property                     *
+*                                                                      *
+*                A copy of the License is available at                 *
+*          http://www.eclipse.org/org/documents/epl-v10.html           *
+*         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *
+*                                                                      *
+*              Information and Software Systems Research               *
+*                            AT&T Research                             *
+*                           Florham Park NJ                            *
+*                                                                      *
+*                 Glenn Fowler <gsf@research.att.com>                  *
+*                  David Korn <dgk@research.att.com>                   *
+*                   Phong Vo <kpv@research.att.com>                    *
+*                                                                      *
+***********************************************************************/
+#pragma prototyped
+
+/*
+ * frexp/ldexp implementation
+ */
+
+#include <ast.h>
+
+#include "FEATURE/float"
+
+#if _lib_frexp && _lib_ldexp
+
+NoN(frexp)
+
+#else
+
+#if defined(_ast_dbl_exp_index) && defined(_ast_dbl_exp_shift)
+
+#define INIT()		_ast_dbl_exp_t _pow_
+#define pow2(i)		(_pow_.f=1,_pow_.e[_ast_dbl_exp_index]+=((i)<<_ast_dbl_exp_shift),_pow_.f)
+
+#else
+
+static double		pow2tab[DBL_MAX_EXP + 1];
+
+static int
+init(void)
+{
+	register int	x;
+	double		g;
+
+	g = 1;
+	for (x = 0; x < elementsof(pow2tab); x++)
+	{
+		pow2tab[x] = g;
+		g *= 2;
+	}
+	return 0;
+}
+
+#define INIT()		(pow2tab[0]?0:init())
+
+#define pow2(i)		pow2tab[i]
+
+#endif
+
+#if !_lib_frexp
+
+extern double
+frexp(double f, int* p)
+{
+	register int	k;
+	register int	x;
+	double		g;
+
+	INIT();
+
+	/*
+	 * normalize
+	 */
+
+	x = k = DBL_MAX_EXP / 2;
+	if (f < 1)
+	{
+		g = 1.0L / f;
+		for (;;)
+		{
+			k = (k + 1) / 2;
+			if (g < pow2(x))
+				x -= k;
+			else if (k == 1 && g < pow2(x+1))
+				break;
+			else
+				x += k;
+		}
+		if (g == pow2(x))
+			x--;
+		x = -x;
+	}
+	else if (f > 1)
+	{
+		for (;;)
+		{
+			k = (k + 1) / 2;
+			if (f > pow2(x))
+				x += k;
+			else if (k == 1 && f > pow2(x-1))
+				break;
+			else
+				x -= k;
+		}
+		if (f == pow2(x))
+			x++;
+	}
+	else
+		x = 1;
+	*p = x;
+
+	/*
+	 * shift
+	 */
+
+	x = -x;
+	if (x < 0)
+		f /= pow2(-x);
+	else if (x < DBL_MAX_EXP)
+		f *= pow2(x);
+	else
+		f = (f * pow2(DBL_MAX_EXP - 1)) * pow2(x - (DBL_MAX_EXP - 1));
+	return f;
+}
+
+#endif
+
+#if !_lib_ldexp
+
+extern double
+ldexp(double f, register int x)
+{
+	INIT();
+	if (x < 0)
+		f /= pow2(-x);
+	else if (x < DBL_MAX_EXP)
+		f *= pow2(x);
+	else
+		f = (f * pow2(DBL_MAX_EXP - 1)) * pow2(x - (DBL_MAX_EXP - 1));
+	return f;
+}
+
+#endif
+
+#endif