s_floor.c

eCos/RedBoot for勤研ARM AnywhereII(4510) 含全部源代码

//===========================================================================
//
//      s_floor.c
//
//      Part of the standard mathematical function library
//
//===========================================================================
//####ECOSGPLCOPYRIGHTBEGIN####
// -------------------------------------------
// This file is part of eCos, the Embedded Configurable Operating System.
// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
//
// eCos is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License along
// with eCos; if not, write to the Free Software Foundation, Inc.,
// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
//
// As a special exception, if other files instantiate templates or use macros
// or inline functions from this file, or you compile this file and link it
// with other works to produce a work based on this file, this file does not
// by itself cause the resulting work to be covered by the GNU General Public
// License. However the source code for this file must still be made available
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// this file might be covered by the GNU General Public License.
//
// Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
// at http://sources.redhat.com/ecos/ecos-license/
// -------------------------------------------
//####ECOSGPLCOPYRIGHTEND####
//===========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):   jlarmour
// Contributors:  jlarmour
// 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_floor.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.
 * ====================================================
 */

/*
 * floor(x)
 * Return x rounded toward -inf to integral value
 * Method:
 *      Bit twiddling.
 * Exception:
 *      Inexact flag raised if x not equal to floor(x).
 */

#include "mathincl/fdlibm.h"

static const double huge = 1.0e300;

        double floor(double x)
{
        int i0,i1,j0;
        unsigned i,j;
        i0 =  CYG_LIBM_HI(x);
        i1 =  CYG_LIBM_LO(x);
        j0 = ((i0>>20)&0x7ff)-0x3ff;
        if(j0<20) {
            if(j0<0) {  /* raise inexact if x != 0 */
                if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
                    if(i0>=0) {i0=i1=0;} 
                    else if(((i0&0x7fffffff)|i1)!=0)
                        { i0=0xbff00000;i1=0;}
                }
            } else {
                i = (0x000fffff)>>j0;
                if(((i0&i)|i1)==0) return x; /* x is integral */
                if(huge+x>0.0) {        /* raise inexact flag */
                    if(i0<0) i0 += (0x00100000)>>j0;
                    i0 &= (~i); i1=0;
                }
            }
        } else if (j0>51) {
            if(j0==0x400) return x+x;   /* inf or NaN */
            else return x;              /* x is integral */
        } else {
            i = ((unsigned)(0xffffffff))>>(j0-20);
            if((i1&i)==0) return x;     /* x is integral */
            if(huge+x>0.0) {            /* raise inexact flag */
                if(i0<0) {
                    if(j0==20) i0+=1; 
                    else {
                        j = i1+(1<<(52-j0));
                        if(j<(unsigned)i1) i0 +=1 ;     /* got a carry */
                        i1=j;
                    }
                }
                i1 &= (~i);
            }
        }
        CYG_LIBM_HI(x) = i0;
        CYG_LIBM_LO(x) = i1;
        return x;
}

#endif // ifdef CYGPKG_LIBM     

// EOF s_floor.c