From 7ce331c01ce6eb7b3f5c715a38a24359da9c6ee2 Mon Sep 17 00:00:00 2001
From: Eric Andersen <andersen@codepoet.org>
Date: Thu, 22 Nov 2001 14:04:29 +0000
Subject: Totally rework the math library, this time based on the MacOs X math
 library (which is itself based on the math lib from FreeBSD).  -Erik

---
 libm/s_scalbn.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 libm/s_scalbn.c

(limited to 'libm/s_scalbn.c')

diff --git a/libm/s_scalbn.c b/libm/s_scalbn.c
new file mode 100644
index 000000000..6534fd4cf
--- /dev/null
+++ b/libm/s_scalbn.c
@@ -0,0 +1,66 @@
+/* @(#)s_scalbn.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+#if defined(LIBM_SCCS) && !defined(lint)
+static char rcsid[] = "$NetBSD: s_scalbn.c,v 1.8 1995/05/10 20:48:08 jtc Exp $";
+#endif
+
+/* 
+ * scalbn (double x, int n)
+ * scalbn(x,n) returns x* 2**n  computed by  exponent  
+ * manipulation rather than by actually performing an 
+ * exponentiation or a multiplication.
+ */
+
+#include "math.h"
+#include "math_private.h"
+
+#ifdef __STDC__
+static const double
+#else
+static double
+#endif
+two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
+twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
+huge   = 1.0e+300,
+tiny   = 1.0e-300;
+
+#ifdef __STDC__
+	double scalbn (double x, int n)
+#else
+	double scalbn (x,n)
+	double x; int n;
+#endif
+{
+	int32_t k,hx,lx;
+	EXTRACT_WORDS(hx,lx,x);
+        k = (hx&0x7ff00000)>>20;		/* extract exponent */
+        if (k==0) {				/* 0 or subnormal x */
+            if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
+	    x *= two54; 
+	    GET_HIGH_WORD(hx,x);
+	    k = ((hx&0x7ff00000)>>20) - 54; 
+            if (n< -50000) return tiny*x; 	/*underflow*/
+	    }
+        if (k==0x7ff) return x+x;		/* NaN or Inf */
+        k = k+n; 
+        if (k >  0x7fe) return huge*copysign(huge,x); /* overflow  */
+        if (k > 0) 				/* normal result */
+	    {SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;}
+        if (k <= -54)
+            if (n > 50000) 	/* in case integer overflow in n+k */
+		return huge*copysign(huge,x);	/*overflow*/
+	    else return tiny*copysign(tiny,x); 	/*underflow*/
+        k += 54;				/* subnormal result */
+	SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));
+        return x*twom54;
+}
-- 
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