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[/] [openrisc/] [trunk/] [rtos/] [ecos-2.0/] [packages/] [language/] [c/] [libm/] [v2_0/] [src/] [double/] [portable-api/] [s_scalbn.c] - Blame information for rev 174

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//===========================================================================
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//
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//      s_scalbn.c
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//
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//      Part of the standard mathematical function library
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//
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//===========================================================================
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//####ECOSGPLCOPYRIGHTBEGIN####
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// -------------------------------------------
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// This file is part of eCos, the Embedded Configurable Operating System.
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// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
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//
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// eCos is free software; you can redistribute it and/or modify it under
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// the terms of the GNU General Public License as published by the Free
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// Software Foundation; either version 2 or (at your option) any later version.
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//
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// eCos is distributed in the hope that it will be useful, but WITHOUT ANY
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or
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// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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// for more details.
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//
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// You should have received a copy of the GNU General Public License along
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// with eCos; if not, write to the Free Software Foundation, Inc.,
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// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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//
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// As a special exception, if other files instantiate templates or use macros
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// or inline functions from this file, or you compile this file and link it
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// with other works to produce a work based on this file, this file does not
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// by itself cause the resulting work to be covered by the GNU General Public
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// License. However the source code for this file must still be made available
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// in accordance with section (3) of the GNU General Public License.
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//
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// This exception does not invalidate any other reasons why a work based on
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// this file might be covered by the GNU General Public License.
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//
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// Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
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// at http://sources.redhat.com/ecos/ecos-license/
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// -------------------------------------------
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//####ECOSGPLCOPYRIGHTEND####
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//===========================================================================
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//#####DESCRIPTIONBEGIN####
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//
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// Author(s):   jlarmour
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// Contributors:  jlarmour
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// Date:        1998-02-13
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// Purpose:     
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// Description: 
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// Usage:       
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//
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//####DESCRIPTIONEND####
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//
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//===========================================================================
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// CONFIGURATION
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#include <pkgconf/libm.h>   // Configuration header
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// Include the Math library?
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#ifdef CYGPKG_LIBM     
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// Derived from code with the following copyright
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/* @(#)s_scalbn.c 1.3 95/01/18 */
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/*
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 * ====================================================
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 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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 *
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 * Developed at SunSoft, a Sun Microsystems, Inc. business.
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 * Permission to use, copy, modify, and distribute this
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 * software is freely granted, provided that this notice
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 * is preserved.
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 * ====================================================
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 */
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/*
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 * scalbn (double x, int n)
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 * scalbn(x,n) returns x* 2**n  computed by  exponent
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 * manipulation rather than by actually performing an
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 * exponentiation or a multiplication.
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 */
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#include "mathincl/fdlibm.h"
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static const double
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two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
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twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
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huge   = 1.0e+300,
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tiny   = 1.0e-300;
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        double scalbn (double x, int n)
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{
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        int  k,hx,lx;
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        hx = CYG_LIBM_HI(x);
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        lx = CYG_LIBM_LO(x);
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        k = (hx&0x7ff00000)>>20;                /* extract exponent */
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        if (k==0) {                             /* 0 or subnormal x */
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            if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
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            x *= two54;
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            hx = CYG_LIBM_HI(x);
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            k = ((hx&0x7ff00000)>>20) - 54;
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            if (n< -50000) return tiny*x;       /*underflow*/
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            }
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        if (k==0x7ff) return x+x;               /* NaN or Inf */
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        k = k+n;
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        if (k >  0x7fe) return huge*copysign(huge,x); /* overflow  */
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        if (k > 0)                              /* normal result */
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            {CYG_LIBM_HI(x) = (hx&0x800fffff)|(k<<20); return x;}
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        if (k <= -54) {
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            if (n > 50000)      /* in case integer overflow in n+k */
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                return huge*copysign(huge,x);   /*overflow*/
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            else return tiny*copysign(tiny,x);  /*underflow*/
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        }
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        k += 54;                                /* subnormal result */
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        CYG_LIBM_HI(x) = (hx&0x800fffff)|(k<<20);
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        return x*twom54;
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}
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#endif // ifdef CYGPKG_LIBM     
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// EOF s_scalbn.c

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