fix

git-svn-id: http://svn2.nishi.boats/svn/milsko/trunk@555 b9cfdab3-6d41-4d17-bbe4-086880011989

src/math/nbsd_scalbn.c

@@ -0,0 +1,65 @@
+/* @(#)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.
+ * ====================================================
+ */
+
+/* $Id$ */
+
+#include <Mw/BaseTypes.h>
+#include "math_internal.h"
+
+/*
+ * 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.
+ */
+
+static const double
+    two54  = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
+    twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
+    hugev  = 1.0e+300,
+    tinyv  = 1.0e-300;
+
+double
+nbsd_scalbn(double x, int n) {
+	return nbsd_scalbln(x, n);
+}
+
+double
+nbsd_scalbln(double x, long n) {
+	MwI32 k, hx, lx;
+	EXTRACT_WORDS(hx, lx, x);
+	k = ((MwU32)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 = (((MwU32)hx & 0x7ff00000) >> 20) - 54;
+		if(n < -50000) return tinyv * x; /*underflow*/
+	}
+	if(k == 0x7ff) return x + x; /* NaN or Inf */
+	k = k + n;
+	if(k > 0x7fe) return hugev * nbsd_copysign(hugev, 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 hugev * nbsd_copysign(hugev, x); /*overflow*/
+		else
+			return tinyv * nbsd_copysign(tinyv, x); /*underflow*/
+	}
+	k += 54; /* subnormal result */
+	SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
+	return x * twom54;
+}