1/* @(#)s_ceil.c 5.1 93/09/24 */
2/*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
11 */
12
13#include <sys/cdefs.h>
14#if defined(LIBM_SCCS) && !defined(lint)
15__RCSID("$NetBSD: s_ceil.c,v 1.13 2009/02/16 01:22:18 lukem Exp $");
16#endif
17
18/*
19 * ceil(x)
20 * Return x rounded toward -inf to integral value
21 * Method:
22 *	Bit twiddling.
23 * Exception:
24 *	Inexact flag raised if x not equal to ceil(x).
25 */
26
27#include "math.h"
28#include "math_private.h"
29
30static const double huge = 1.0e300;
31
32#ifndef __HAVE_LONG_DOUBLE
33__strong_alias(_ceill, ceil)
34__weak_alias(ceill, ceil)
35#endif
36
37double
38ceil(double x)
39{
40	int32_t i0,i1,jj0;
41	u_int32_t i,j;
42	EXTRACT_WORDS(i0,i1,x);
43	jj0 = ((i0>>20)&0x7ff)-0x3ff;
44	if(jj0<20) {
45	    if(jj0<0) { 	/* raise inexact if x != 0 */
46		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
47		    if(i0<0) {i0=0x80000000;i1=0;}
48		    else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;}
49		}
50	    } else {
51		i = (0x000fffff)>>jj0;
52		if(((i0&i)|i1)==0) return x; /* x is integral */
53		if(huge+x>0.0) {	/* raise inexact flag */
54		    if(i0>0) i0 += (0x00100000)>>jj0;
55		    i0 &= (~i); i1=0;
56		}
57	    }
58	} else if (jj0>51) {
59	    if(jj0==0x400) return x+x;	/* inf or NaN */
60	    else return x;		/* x is integral */
61	} else {
62	    i = ((u_int32_t)(0xffffffff))>>(jj0-20);
63	    if((i1&i)==0) return x;	/* x is integral */
64	    if(huge+x>0.0) { 		/* raise inexact flag */
65		if(i0>0) {
66		    if(jj0==20) i0+=1;
67		    else {
68			j = i1 + (1<<(52-jj0));
69			if(j<(u_int32_t)i1) i0+=1;	/* got a carry */
70			i1 = j;
71		    }
72		}
73		i1 &= (~i);
74	    }
75	}
76	INSERT_WORDS(x,i0,i1);
77	return x;
78}
79