logbf.c File Reference

#include "libm.h"
#include "libm_util.h"
#include "libm_inlines.h"
#include "libm_errno.h"

Include dependency graph for logbf.c:

Go to the source code of this file.

Macros
#define	USE_INFINITYF_WITH_FLAGS
#define	USE_HANDLE_ERRORF

Functions
float	_logbf (float x)

Macro Definition Documentation

USE_HANDLE_ERRORF

#define USE_HANDLE_ERRORF

Definition at line 31 of file logbf.c.

USE_INFINITYF_WITH_FLAGS

#define USE_INFINITYF_WITH_FLAGS

Definition at line 30 of file logbf.c.

Function Documentation

_logbf()

float _logbf

(

float

x

)

Definition at line 38 of file logbf.c.

{
  unsigned int ux;
  int u;
  GET_BITS_SP32(x, ux);
  u = ((ux & EXPBITS_SP32) >> EXPSHIFTBITS_SP32) - EXPBIAS_SP32;
  if ((ux & ~SIGNBIT_SP32) == 0)
    /* x is +/-zero. Return -infinity with div-by-zero flag. */
    return _handle_errorf("_logbf", OP_LOGB, NINFBITPATT_SP32, _SING,
                         AMD_F_DIVBYZERO, ERANGE, x, 0.0F, 1);
  else if (EMIN_SP32 <= u && u <= EMAX_SP32)
    /* x is a normal number */
    return (float)u;
  else if (u > EMAX_SP32)
    {
      /* x is infinity or NaN */
      if ((ux & MANTBITS_SP32) == 0)
        /* x is +/-infinity. For VC++, return infinity of same sign. */
        return x;
      else
        /* x is NaN, result is NaN */
        return _handle_errorf("_logbf", OP_LOGB, ux|0x00400000, _DOMAIN,
                             0, EDOM, x, 0.0F, 1);
    }
  else
    {
      /* x is denormalized. */
#ifdef FOLLOW_IEEE754_LOGB
      /* Return the value of the minimum exponent to ensure that
         the relationship between logb and scalb, defined in
         IEEE 754, holds. */
      return EMIN_SP32;
#else
      /* Follow the rule set by IEEE 854 for logb */
      ux &= MANTBITS_SP32;
      u = EMIN_SP32;
      while (ux < IMPBIT_SP32)
        {
          ux <<= 1;
          u--;
        }
      return (float)u;
#endif
    }
}