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/* 2009 for Newlib: Sun's sf_ilogb.c converted to be sf_logb.c. */
/*
* ====================================================
* 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.
* ====================================================
*/
/* float logb(float x)
* return the binary exponent of non-zero x
* logbf(0) = -inf, raise divide-by-zero floating point exception
* logbf(+inf|-inf) = +inf (no signal is raised)
* logbf(NaN) = NaN (no signal is raised)
* Per C99 recommendation, a NaN argument is returned unchanged.
*/
#include "fdlibm.h"
float
#ifdef __STDC__
logbf(float x)
#else
logbf(x)
float x;
#endif
{
__int32_t hx,ix;
GET_FLOAT_WORD(hx,x);
hx &= 0x7fffffff;
if(FLT_UWORD_IS_ZERO(hx)) {
float xx;
/* arg==0: return -inf and raise divide-by-zero exception */
SET_FLOAT_WORD(xx,hx); /* +0.0 */
return -1./xx; /* logbf(0) = -inf */
}
if(FLT_UWORD_IS_SUBNORMAL(hx)) {
for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;
return (float) ix;
}
else if (FLT_UWORD_IS_INFINITE(hx)) return HUGE_VALF; /* x==+|-inf */
else if (FLT_UWORD_IS_NAN(hx)) return x;
else return (float) ((hx>>23)-127);
}
#ifdef _DOUBLE_IS_32BITS
#ifdef __STDC__
double logb(double x)
#else
double logb(x)
double x;
#endif
{
return (double) logbf((float) x);
}
#endif /* defined(_DOUBLE_IS_32BITS) */
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