mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-11 15:50:06 +00:00
49 lines
1.5 KiB
C
49 lines
1.5 KiB
C
/* Copyright (C) 1992, 1995 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Library General Public License as
|
|
published by the Free Software Foundation; either version 2 of the
|
|
License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Library General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Library General Public
|
|
License along with the GNU C Library; see the file COPYING.LIB. If
|
|
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
|
|
Cambridge, MA 02139, USA. */
|
|
|
|
#include <ansidecl.h>
|
|
#include <math.h>
|
|
#include <float.h>
|
|
#include "ieee754.h"
|
|
|
|
/* Return the base 2 signed integral exponent of X. */
|
|
double
|
|
DEFUN(__logb, (x), double x)
|
|
{
|
|
union ieee754_double u;
|
|
|
|
if (__isnan (x))
|
|
return x;
|
|
else if (__isinf (x))
|
|
return HUGE_VAL;
|
|
else if (x == 0.0)
|
|
return - HUGE_VAL;
|
|
|
|
u.d = x;
|
|
|
|
if (u.ieee.exponent == 0)
|
|
/* A denormalized number.
|
|
Multiplying by 2 ** DBL_MANT_DIG normalizes it;
|
|
we then subtract the DBL_MANT_DIG we added to the exponent. */
|
|
return (__logb (x * ldexp (1.0, DBL_MANT_DIG)) - DBL_MANT_DIG);
|
|
|
|
return (int) u.ieee.exponent - (DBL_MAX_EXP - 1);
|
|
}
|
|
|
|
weak_alias (__logb, logb)
|