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/* $OpenBSD: s_ilogbl.c,v 1.2 2016/09/12 19:47:02 guenther Exp $ */
/*
* From: @(#)s_ilogb.c 5.1 93/09/24
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
#include <sys/types.h>
#include <machine/ieee.h>
#include <float.h>
#include <limits.h>
#include <math.h>
int
ilogbl(long double x)
{
struct ieee_ext *p = (struct ieee_ext *)&x;
unsigned long m;
int b;
if (p->ext_exp == 0) {
if ((p->ext_fracl
#ifdef EXT_FRACLMBITS
| p->ext_fraclm
#endif /* EXT_FRACLMBITS */
#ifdef EXT_FRACHMBITS
| p->ext_frachm
#endif /* EXT_FRACHMBITS */
| p->ext_frach) == 0)
return (FP_ILOGB0);
/* denormalized */
if (p->ext_frach == 0
#ifdef EXT_FRACHMBITS
&& p->ext_frachm == 0
#endif
) {
m = 1lu << (EXT_FRACLBITS - 1);
for (b = EXT_FRACHBITS; !(p->ext_fracl & m); m >>= 1)
b++;
#if defined(EXT_FRACHMBITS) && defined(EXT_FRACLMBITS)
m = 1lu << (EXT_FRACLMBITS - 1);
for (b += EXT_FRACHMBITS; !(p->ext_fraclm & m); m >>= 1)
b++;
#endif /* defined(EXT_FRACHMBITS) && defined(EXT_FRACLMBITS) */
} else {
m = 1lu << (EXT_FRACHBITS - 1);
for (b = 0; !(p->ext_frach & m); m >>= 1)
b++;
#ifdef EXT_FRACHMBITS
m = 1lu << (EXT_FRACHMBITS - 1);
for (; !(p->ext_frachm & m); m >>= 1)
b++;
#endif /* EXT_FRACHMBITS */
}
#ifdef EXT_IMPLICIT_NBIT
b++;
#endif
return (LDBL_MIN_EXP - b - 1);
} else if (p->ext_exp < (LDBL_MAX_EXP << 1) - 1)
return (p->ext_exp - LDBL_MAX_EXP + 1);
else if (p->ext_fracl != 0
#ifdef EXT_FRACLMBITS
|| p->ext_fraclm != 0
#endif /* EXT_FRACLMBITS */
#ifdef EXT_FRACHMBITS
|| p->ext_frachm != 0
#endif /* EXT_FRACHMBITS */
|| p->ext_frach != 0)
return (FP_ILOGBNAN);
else
return (INT_MAX);
}
DEF_STD(ilogbl);
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