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.
53 lines
1.2 KiB
C
53 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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#include <sys/cdefs.h>
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#if defined(LIBM_SCCS) && !defined(lint)
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__RCSID("$NetBSD: s_ilogb.c,v 1.13 2011/07/28 22:32:29 joerg 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) = 0x80000001
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* ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
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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(ilogbl,ilogb)
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#endif
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int
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ilogb(double x)
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{
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int32_t hx,lx,ix;
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GET_HIGH_WORD(hx,x);
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hx &= 0x7fffffff;
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if(hx<0x00100000) {
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GET_LOW_WORD(lx,x);
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if((hx|lx)==0)
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return 0x80000001; /* ilogb(0) = 0x80000001 */
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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 return 0x7fffffff;
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}
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