diff packages/language/c/libm/current/src/double/portable-api/s_scalbn.c @ 0:3111d98ba7b3 ecos-v1_1-release

Initial commit of eCos version 1.1
author jlarmour
date Tue, 11 May 1999 11:16:07 +0000
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+//===========================================================================
+//
+//      s_scalbn.c
+//
+//      Part of the standard mathematical function library
+//
+//===========================================================================
+//####COPYRIGHTBEGIN####
+//
+// -------------------------------------------
+// The contents of this file are subject to the Cygnus eCos Public License
+// Version 1.0 (the "License"); you may not use this file except in
+// compliance with the License.  You may obtain a copy of the License at
+// http://sourceware.cygnus.com/ecos
+// 
+// Software distributed under the License is distributed on an "AS IS"
+// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See the
+// License for the specific language governing rights and limitations under
+// the License.
+// 
+// The Original Code is eCos - Embedded Cygnus Operating System, released
+// September 30, 1998.
+// 
+// The Initial Developer of the Original Code is Cygnus.  Portions created
+// by Cygnus are Copyright (C) 1998 Cygnus Solutions.  All Rights Reserved.
+// -------------------------------------------
+//
+//####COPYRIGHTEND####
+//===========================================================================
+//#####DESCRIPTIONBEGIN####
+//
+// Author(s):   jlarmour@cygnus.co.uk
+// Contributors:  jlarmour@cygnus.co.uk
+// Date:        1998-02-13
+// Purpose:     
+// Description: 
+// Usage:       
+//
+//####DESCRIPTIONEND####
+//
+//===========================================================================
+
+// CONFIGURATION
+
+#include <pkgconf/libm.h>   // Configuration header
+
+// Include the Math library?
+#ifdef CYGPKG_LIBM     
+
+// Derived from code with the following copyright
+
+
+/* @(#)s_scalbn.c 1.3 95/01/18 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunSoft, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+/* 
+ * 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 "mathincl/fdlibm.h"
+
+static const double
+two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
+twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
+huge   = 1.0e+300,
+tiny   = 1.0e-300;
+
+        double scalbn (double x, int n)
+{
+        int  k,hx,lx;
+        hx = CYG_LIBM_HI(x);
+        lx = CYG_LIBM_LO(x);
+        k = (hx&0x7ff00000)>>20;                /* extract exponent */
+        if (k==0) {                             /* 0 or subnormal x */
+            if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
+            x *= two54; 
+            hx = CYG_LIBM_HI(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 */
+            {CYG_LIBM_HI(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 */
+        CYG_LIBM_HI(x) = (hx&0x800fffff)|(k<<20);
+        return x*twom54;
+}
+
+#endif // ifdef CYGPKG_LIBM     
+
+// EOF s_scalbn.c