Subversion Repositories openrisc_2011-10-31

/* @(#)z_frexp.c 1.0 98/08/13 */

/*

FUNCTION

       <<frexp>>, <<frexpf>>---split floating-point number

INDEX

        frexp

INDEX

        frexpf

ANSI_SYNOPSIS

        #include <math.h>

        double frexp(double <[val]>, int *<[exp]>);

        float frexpf(float <[val]>, int *<[exp]>);

TRAD_SYNOPSIS

        #include <math.h>

        double frexp(<[val]>, <[exp]>)

        double <[val]>;

        int *<[exp]>;

        float frexpf(<[val]>, <[exp]>)

        float <[val]>;

        int *<[exp]>;

DESCRIPTION

        All nonzero, normal numbers can be described as <[m]> * 2**<[p]>.

        <<frexp>> represents the double <[val]> as a mantissa <[m]>

        and a power of two <[p]>. The resulting mantissa will always

        be greater than or equal to <<0.5>>, and less than <<1.0>> (as

        long as <[val]> is nonzero). The power of two will be stored

        in <<*>><[exp]>.

@ifnottex

<[m]> and <[p]> are calculated so that

<[val]> is <[m]> times <<2>> to the power <[p]>.

@end ifnottex

@tex

<[m]> and <[p]> are calculated so that

$ val = m \times 2^p $.

@end tex

<<frexpf>> is identical, other than taking and returning

floats rather than doubles.

RETURNS

<<frexp>> returns the mantissa <[m]>. If <[val]> is <<0>>, infinity,

or Nan, <<frexp>> will set <<*>><[exp]> to <<0>> and return <[val]>.

PORTABILITY

<<frexp>> is ANSI.

<<frexpf>> is an extension.

*/

/*****************************************************************

 * frexp

 *

 * Input:

 *   d   - floating point value

 *   exp - exponent value

 *

 * Output:

 *   A floating point value in the range [0.5, 1).

 *

 * Description:

 *   This routine breaks a floating point value into a number f and

 *   an exponent exp such that d = f * 2 ^ exp.

 *

 *****************************************************************/

#include "fdlibm.h"

#include "zmath.h"

#ifndef _DOUBLE_IS_32BITS

double frexp (double d, int *exp)

{

  double f;

  __uint32_t hd, ld, hf, lf;

  /* Check for special values. */

  switch (numtest (d))

    {

      case NAN:

      case INF:

        errno = EDOM;

      case 0:

        *exp = 0;

        return (d);

    }

  EXTRACT_WORDS (hd, ld, d);

  /* Get the exponent. */

  *exp = ((hd & 0x7ff00000) >> 20) - 1022;

  /* Get the mantissa. */

  lf = ld;

  hf = hd & 0x800fffff;

  hf |= 0x3fe00000;

  INSERT_WORDS (f, hf, lf);

  return (f);

}

#endif /* _DOUBLE_IS_32BITS */