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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [mathfp/] [s_frexp.c] - Blame information for rev 207

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1 207 jeremybenn
 
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/* @(#)z_frexp.c 1.0 98/08/13 */
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/*
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FUNCTION
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       <<frexp>>, <<frexpf>>---split floating-point number
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INDEX
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        frexp
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INDEX
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        frexpf
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ANSI_SYNOPSIS
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        #include <math.h>
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        double frexp(double <[val]>, int *<[exp]>);
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        float frexpf(float <[val]>, int *<[exp]>);
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TRAD_SYNOPSIS
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        #include <math.h>
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        double frexp(<[val]>, <[exp]>)
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        double <[val]>;
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        int *<[exp]>;
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        float frexpf(<[val]>, <[exp]>)
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        float <[val]>;
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        int *<[exp]>;
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DESCRIPTION
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        All nonzero, normal numbers can be described as <[m]> * 2**<[p]>.
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        <<frexp>> represents the double <[val]> as a mantissa <[m]>
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        and a power of two <[p]>. The resulting mantissa will always
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        be greater than or equal to <<0.5>>, and less than <<1.0>> (as
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        long as <[val]> is nonzero). The power of two will be stored
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        in <<*>><[exp]>.
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@ifnottex
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<[m]> and <[p]> are calculated so that
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<[val]> is <[m]> times <<2>> to the power <[p]>.
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@end ifnottex
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@tex
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<[m]> and <[p]> are calculated so that
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$ val = m \times 2^p $.
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@end tex
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<<frexpf>> is identical, other than taking and returning
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floats rather than doubles.
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RETURNS
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<<frexp>> returns the mantissa <[m]>. If <[val]> is <<0>>, infinity,
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or Nan, <<frexp>> will set <<*>><[exp]> to <<0>> and return <[val]>.
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PORTABILITY
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<<frexp>> is ANSI.
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<<frexpf>> is an extension.
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*/
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/*****************************************************************
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 * frexp
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 *
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 * Input:
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 *   d   - floating point value
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 *   exp - exponent value
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 *
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 * Output:
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 *   A floating point value in the range [0.5, 1).
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 *
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 * Description:
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 *   This routine breaks a floating point value into a number f and
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 *   an exponent exp such that d = f * 2 ^ exp.
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 *
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 *****************************************************************/
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#include "fdlibm.h"
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#include "zmath.h"
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#ifndef _DOUBLE_IS_32BITS
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double frexp (double d, int *exp)
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{
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  double f;
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  __uint32_t hd, ld, hf, lf;
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  /* Check for special values. */
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  switch (numtest (d))
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    {
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      case NAN:
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      case INF:
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        errno = EDOM;
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      case 0:
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        *exp = 0;
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        return (d);
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    }
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  EXTRACT_WORDS (hd, ld, d);
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  /* Get the exponent. */
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  *exp = ((hd & 0x7ff00000) >> 20) - 1022;
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  /* Get the mantissa. */
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  lf = ld;
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  hf = hd & 0x800fffff;
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  hf |= 0x3fe00000;
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  INSERT_WORDS (f, hf, lf);
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  return (f);
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}
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#endif /* _DOUBLE_IS_32BITS */

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