Mercurial > nand-ecoscentric
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 |
| parents | |
| children | 443894e2e912 |
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new file mode 100644 --- /dev/null +++ b/packages/language/c/libm/current/src/double/portable-api/s_scalbn.c @@ -0,0 +1,110 @@ +//=========================================================================== +// +// 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
