xref: /illumos-gate/usr/src/lib/libm/common/C/ceil.c (revision ddc0e0b5)
125c28e83SPiotr Jasiukajtis /*
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2125c28e83SPiotr Jasiukajtis /*
2225c28e83SPiotr Jasiukajtis  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
2325c28e83SPiotr Jasiukajtis  */
2425c28e83SPiotr Jasiukajtis /*
2525c28e83SPiotr Jasiukajtis  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
2625c28e83SPiotr Jasiukajtis  * Use is subject to license terms.
2725c28e83SPiotr Jasiukajtis  */
2825c28e83SPiotr Jasiukajtis 
29*ddc0e0b5SRichard Lowe #pragma weak __ceil = ceil
3025c28e83SPiotr Jasiukajtis 
3125c28e83SPiotr Jasiukajtis /*
3225c28e83SPiotr Jasiukajtis  * ceil(x) returns the least integral value bigger than or equal to x.
3325c28e83SPiotr Jasiukajtis  * NOTE: ceil(x) returns result with the same sign as x's, including 0.
3425c28e83SPiotr Jasiukajtis  *
3525c28e83SPiotr Jasiukajtis  * Modified 8/4/04 for performance.
3625c28e83SPiotr Jasiukajtis  */
3725c28e83SPiotr Jasiukajtis 
3825c28e83SPiotr Jasiukajtis #include "libm.h"
3925c28e83SPiotr Jasiukajtis 
4025c28e83SPiotr Jasiukajtis static const double
4125c28e83SPiotr Jasiukajtis 	zero = 0.0,
4225c28e83SPiotr Jasiukajtis 	one = 1.0,
4325c28e83SPiotr Jasiukajtis 	two52 = 4503599627370496.0;
4425c28e83SPiotr Jasiukajtis 
4525c28e83SPiotr Jasiukajtis double
ceil(double x)4625c28e83SPiotr Jasiukajtis ceil(double x) {
4725c28e83SPiotr Jasiukajtis 	double	t, w;
4825c28e83SPiotr Jasiukajtis 	int	hx, lx, ix;
4925c28e83SPiotr Jasiukajtis 
5025c28e83SPiotr Jasiukajtis 	hx = ((int *)&x)[HIWORD];
5125c28e83SPiotr Jasiukajtis 	lx = ((int *)&x)[LOWORD];
5225c28e83SPiotr Jasiukajtis 	ix = hx & ~0x80000000;
5325c28e83SPiotr Jasiukajtis 	if (ix >= 0x43300000)	/* return x if |x| >= 2^52, or x is NaN */
5425c28e83SPiotr Jasiukajtis 		return (x * one);
5525c28e83SPiotr Jasiukajtis 	t = (hx >= 0)? two52 : -two52;
5625c28e83SPiotr Jasiukajtis 	w = x + t;
5725c28e83SPiotr Jasiukajtis 	t = w - t;
5825c28e83SPiotr Jasiukajtis 	if (ix < 0x3ff00000) {
5925c28e83SPiotr Jasiukajtis 		if ((ix | lx) == 0)
6025c28e83SPiotr Jasiukajtis 			return (x);
6125c28e83SPiotr Jasiukajtis 		else
6225c28e83SPiotr Jasiukajtis 			return ((hx < 0)? -zero : one);
6325c28e83SPiotr Jasiukajtis 	}
6425c28e83SPiotr Jasiukajtis 	return ((t >= x)? t : t + one);
6525c28e83SPiotr Jasiukajtis }
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