5980be9b3c
This work is based in part on code from NetBSD libm, libc and kernel. The library is partly public domain and partly BSD-style licensed.
44 lines
1 KiB
C
44 lines
1 KiB
C
/* @(#)s_logb.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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#include <sys/cdefs.h>
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#if defined(LIBM_SCCS) && !defined(lint)
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__RCSID("$NetBSD: s_logb.c,v 1.12 2011/08/03 14:13:07 joerg Exp $");
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#endif
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/*
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* double logb(x)
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* IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
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* Use ilogb instead.
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*/
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#include "math.h"
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#include "math_private.h"
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#ifndef __HAVE_LONG_DOUBLE
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__strong_alias(logbl,logb)
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#endif
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double
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logb(double x)
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{
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int32_t lx,ix;
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EXTRACT_WORDS(ix,lx,x);
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ix &= 0x7fffffff; /* high |x| */
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if((ix|lx)==0) return -1.0/fabs(x);
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if(ix>=0x7ff00000) return x*x;
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if((ix>>=20)==0) /* IEEE 754 logb */
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return -1022.0;
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else
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return (double) (ix-1023);
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}
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