50 lines
1.2 KiB
C
50 lines
1.2 KiB
C
/* @(#)s_ilogb.c 5.1 93/09/24 */
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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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#ifndef lint
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static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_ilogb.c,v 1.9 2004/10/09 17:14:28 stefanf Exp $";
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#endif
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/* ilogb(double x)
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* return the binary exponent of non-zero x
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* ilogb(0) = FP_ILOGB0
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* ilogb(NaN) = FP_ILOGBNAN (no signal is raised)
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* ilogb(inf) = INT_MAX (no signal is raised)
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*/
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#include <limits.h>
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#include "math.h"
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#include "math_private.h"
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int ilogb(double x)
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{
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int32_t hx,lx,ix;
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EXTRACT_WORDS(hx,lx,x);
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hx &= 0x7fffffff;
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if(hx<0x00100000) {
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if((hx|lx)==0)
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return FP_ILOGB0;
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else /* subnormal x */
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if(hx==0) {
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for (ix = -1043; lx>0; lx<<=1) ix -=1;
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} else {
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for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;
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}
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return ix;
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}
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else if (hx<0x7ff00000) return (hx>>20)-1023;
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else if (hx>0x7ff00000 || lx!=0) return FP_ILOGBNAN;
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else return INT_MAX;
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}
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