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[/] [openrisc/] [trunk/] [gnu-old/] [newlib-1.17.0/] [newlib/] [libm/] [common/] [s_modf.c] - Blame information for rev 816

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1 148 jeremybenn
 
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/* @(#)s_modf.c 5.1 93/09/24 */
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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 SunPro, 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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FUNCTION
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       <<modf>>, <<modff>>---split fractional and integer parts
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INDEX
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        modf
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INDEX
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        modff
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ANSI_SYNOPSIS
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        #include <math.h>
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        double modf(double <[val]>, double *<[ipart]>);
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        float modff(float <[val]>, float *<[ipart]>);
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TRAD_SYNOPSIS
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        #include <math.h>
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        double modf(<[val]>, <[ipart]>)
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        double <[val]>;
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        double *<[ipart]>;
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        float modff(<[val]>, <[ipart]>)
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        float <[val]>;
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        float *<[ipart]>;
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DESCRIPTION
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        <<modf>> splits the double <[val]> apart into an integer part
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        and a fractional part, returning the fractional part and
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        storing the integer part in <<*<[ipart]>>>.  No rounding
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        whatsoever is done; the sum of the integer and fractional
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        parts is guaranteed to be exactly  equal to <[val]>.   That
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        is, if <[realpart]> = modf(<[val]>, &<[intpart]>); then
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        `<<<[realpart]>+<[intpart]>>>' is the same as <[val]>.
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        <<modff>> is identical, save that it takes and returns
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        <<float>> rather than <<double>> values.
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RETURNS
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        The fractional part is returned.  Each result has the same
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        sign as the supplied argument <[val]>.
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PORTABILITY
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        <<modf>> is ANSI C. <<modff>> is an extension.
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QUICKREF
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        modf  ansi pure
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        modff - pure
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*/
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/*
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 * modf(double x, double *iptr)
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 * return fraction part of x, and return x's integral part in *iptr.
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 * Method:
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 *      Bit twiddling.
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 *
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 * Exception:
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 *      No exception.
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 */
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#include "fdlibm.h"
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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static const double one = 1.0;
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#else
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static double one = 1.0;
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#endif
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#ifdef __STDC__
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        double modf(double x, double *iptr)
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#else
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        double modf(x, iptr)
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        double x,*iptr;
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#endif
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{
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        __int32_t i0,i1,j0;
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        __uint32_t i;
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        EXTRACT_WORDS(i0,i1,x);
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        j0 = ((i0>>20)&0x7ff)-0x3ff;    /* exponent of x */
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        if(j0<20) {                     /* integer part in high x */
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            if(j0<0) {                   /* |x|<1 */
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                INSERT_WORDS(*iptr,i0&0x80000000,0);     /* *iptr = +-0 */
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                return x;
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            } else {
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                i = (0x000fffff)>>j0;
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                if(((i0&i)|i1)==0) {             /* x is integral */
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                    __uint32_t high;
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                    *iptr = x;
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                    GET_HIGH_WORD(high,x);
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                    INSERT_WORDS(x,high&0x80000000,0);   /* return +-0 */
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                    return x;
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                } else {
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                    INSERT_WORDS(*iptr,i0&(~i),0);
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                    return x - *iptr;
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                }
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            }
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        } else if (j0>51) {             /* no fraction part */
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            __uint32_t high;
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            *iptr = x*one;
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            GET_HIGH_WORD(high,x);
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            INSERT_WORDS(x,high&0x80000000,0);   /* return +-0 */
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            return x;
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        } else {                        /* fraction part in low x */
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            i = ((__uint32_t)(0xffffffff))>>(j0-20);
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            if((i1&i)==0) {              /* x is integral */
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                __uint32_t high;
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                *iptr = x;
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                GET_HIGH_WORD(high,x);
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                INSERT_WORDS(x,high&0x80000000,0);       /* return +-0 */
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                return x;
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            } else {
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                INSERT_WORDS(*iptr,i0,i1&(~i));
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                return x - *iptr;
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            }
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        }
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}
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#endif /* _DOUBLE_IS_32BITS */

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