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WebSVN – planix.SVN – Blame – /os/branches/feature_unix/sys/src/ape/lib/ap/math/modf.c – Rev 2

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#include <math.h>
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#include <errno.h>
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/* modf suitable for IEEE double-precision */
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#define	MASK	0x7ffL
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#define SIGN	0x80000000
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#define	SHIFT	20
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#define	BIAS	1022L
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typedef	union
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{
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	double	d;
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	struct
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	{
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		long	ms;
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		long	ls;
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	} i;
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} Cheat;
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double
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modf(double d, double *ip)
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{
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	Cheat x;
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	int e;
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	if(-1 < d && d < 1) {
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		*ip = 0;
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		return d;
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	}
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	x.d = d;
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	x.i.ms &= ~SIGN;
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	e = (x.i.ms >> SHIFT) & MASK;
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	if(e == MASK || e == 0){
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		errno = EDOM;
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		*ip = (d > 0)? HUGE_VAL : -HUGE_VAL;
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		return 0;
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	}
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	e -= BIAS;
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	if(e <= SHIFT+1) {
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		x.i.ms &= ~(0x1fffffL >> e);
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		x.i.ls = 0;
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	} else
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	if(e <= SHIFT+33)
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		x.i.ls &= ~(0x7fffffffL >> (e-SHIFT-2));
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	if(d > 0){
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		*ip = x.d;
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		return d - x.d;
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	}else{
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		*ip = -x.d;
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		return d + x.d;
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	}
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}