Initial revision

From-SVN: r26263

libjava/java/lang/s_scalbn.c

@@ -0,0 +1,104 @@
+
+/* @(#)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.
+ * ====================================================
+ */
+
+/*
+FUNCTION
+<<scalbn>>, <<scalbnf>>---scale by integer
+INDEX
+	scalbn
+INDEX
+	scalbnf
+
+ANSI_SYNOPSIS
+	#include <math.h>
+	double scalbn(double <[x]>, int <[y]>);
+	float scalbnf(float <[x]>, int <[y]>);
+
+TRAD_SYNOPSIS
+	#include <math.h>
+	double scalbn(<[x]>,<[y]>)
+	double <[x]>;
+	int <[y]>;
+	float scalbnf(<[x]>,<[y]>)
+	float <[x]>;
+	int <[y]>;
+
+DESCRIPTION
+<<scalbn>> and <<scalbnf>> scale <[x]> by <[n]>, returning <[x]> times
+2 to the power <[n]>.  The result is computed by manipulating the
+exponent, rather than by actually performing an exponentiation or
+multiplication.
+
+RETURNS
+<[x]> times 2 to the power <[n]>.
+
+PORTABILITY
+Neither <<scalbn>> nor <<scalbnf>> is required by ANSI C or by the System V
+Interface Definition (Issue 2).
+
+*/
+
+/* 
+ * 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 "fdlibm.h"
+
+#ifndef _DOUBLE_IS_32BITS
+
+#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;
+}
+
+#endif /* _DOUBLE_IS_32BITS */