55 lines
1.2 KiB
C
55 lines
1.2 KiB
C
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/*
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* From: @(#)s_ilogb.c 5.1 93/09/24
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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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__FBSDID("$FreeBSD$");
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#include <float.h>
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#include <limits.h>
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#include <math.h>
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#include "fpmath.h"
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long double
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logbl(long double x)
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{
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union IEEEl2bits u;
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unsigned long m;
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int b;
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u.e = x;
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if (u.bits.exp == 0) {
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if ((u.bits.manl | u.bits.manh) == 0) { /* x == 0 */
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u.bits.sign = 1;
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return (1.0L / u.e);
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}
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/* denormalized */
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if (u.bits.manh == 0) {
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m = 1lu << (LDBL_MANL_SIZE - 1);
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for (b = LDBL_MANH_SIZE; !(u.bits.manl & m); m >>= 1)
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b++;
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} else {
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m = 1lu << (LDBL_MANH_SIZE - 1);
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for (b = 0; !(u.bits.manh & m); m >>= 1)
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b++;
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}
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#ifdef LDBL_IMPLICIT_NBIT
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b++;
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#endif
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return ((long double)(LDBL_MIN_EXP - b - 1));
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}
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if (u.bits.exp < (LDBL_MAX_EXP << 1) - 1) /* normal */
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return ((long double)(u.bits.exp - LDBL_MAX_EXP + 1));
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else /* +/- inf or nan */
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return (x * x);
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}
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