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63 lines
1.5 KiB
C
63 lines
1.5 KiB
C
/* 2009 for Newlib: Sun's sf_ilogb.c converted to be sf_logb.c. */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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/* float logb(float x)
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* return the binary exponent of non-zero x
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* logbf(0) = -inf, raise divide-by-zero floating point exception
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* logbf(+inf|-inf) = +inf (no signal is raised)
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* logbf(NaN) = NaN (no signal is raised)
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* Per C99 recommendation, a NaN argument is returned unchanged.
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*/
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#include "fdlibm.h"
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float
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#ifdef __STDC__
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logbf(float x)
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#else
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logbf(x)
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float x;
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#endif
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{
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__int32_t hx,ix;
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GET_FLOAT_WORD(hx,x);
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hx &= 0x7fffffff;
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if(FLT_UWORD_IS_ZERO(hx)) {
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float xx;
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/* arg==0: return -inf and raise divide-by-zero exception */
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SET_FLOAT_WORD(xx,hx); /* +0.0 */
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return -1./xx; /* logbf(0) = -inf */
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}
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if(FLT_UWORD_IS_SUBNORMAL(hx)) {
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for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;
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return (float) ix;
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}
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else if (FLT_UWORD_IS_INFINITE(hx)) return HUGE_VALF; /* x==+|-inf */
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else if (FLT_UWORD_IS_NAN(hx)) return x;
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else return (float) ((hx>>23)-127);
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}
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#ifdef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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double logb(double x)
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#else
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double logb(x)
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double x;
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#endif
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{
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return (double) logbf((float) x);
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */
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