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42 lines
1.0 KiB
C
42 lines
1.0 KiB
C
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/* @(#)s_ilogb.c 1.3 95/01/18 */
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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 SunSoft, 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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/* 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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int ilogb(double x) {
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int hx, lx, ix;
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hx = (__HI(x)) & 0x7fffffff; /* high word of x */
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if(hx < 0x00100000) {
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lx = __LO(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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} else if(hx < 0x7ff00000)
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return (hx >> 20) - 1023;
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else
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return 0x7fffffff;
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}
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