xref: /freebsd/lib/msun/src/s_ceil.c (revision f3c5273d315a64826d2149ac453ff8c4583ddbe8)
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 __FBSDID("$FreeBSD$");
15 
16 /*
17  * ceil(x)
18  * Return x rounded toward -inf to integral value
19  * Method:
20  *	Bit twiddling.
21  * Exception:
22  *	Inexact flag raised if x not equal to ceil(x).
23  */
24 
25 #include <float.h>
26 
27 #include "math.h"
28 #include "math_private.h"
29 
30 static const double huge = 1.0e300;
31 
32 double
33 ceil(double x)
34 {
35 	int32_t i0,i1,j0;
36 	u_int32_t i,j;
37 	EXTRACT_WORDS(i0,i1,x);
38 	j0 = ((i0>>20)&0x7ff)-0x3ff;
39 	if(j0<20) {
40 	    if(j0<0) { 	/* raise inexact if x != 0 */
41 		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
42 		    if(i0<0) {i0=0x80000000;i1=0;}
43 		    else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;}
44 		}
45 	    } else {
46 		i = (0x000fffff)>>j0;
47 		if(((i0&i)|i1)==0) return x; /* x is integral */
48 		if(huge+x>0.0) {	/* raise inexact flag */
49 		    if(i0>0) i0 += (0x00100000)>>j0;
50 		    i0 &= (~i); i1=0;
51 		}
52 	    }
53 	} else if (j0>51) {
54 	    if(j0==0x400) return x+x;	/* inf or NaN */
55 	    else return x;		/* x is integral */
56 	} else {
57 	    i = ((u_int32_t)(0xffffffff))>>(j0-20);
58 	    if((i1&i)==0) return x;	/* x is integral */
59 	    if(huge+x>0.0) { 		/* raise inexact flag */
60 		if(i0>0) {
61 		    if(j0==20) i0+=1;
62 		    else {
63 			j = i1 + (1<<(52-j0));
64 			if(j<i1) i0+=1;	/* got a carry */
65 			i1 = j;
66 		    }
67 		}
68 		i1 &= (~i);
69 	    }
70 	}
71 	INSERT_WORDS(x,i0,i1);
72 	return x;
73 }
74 
75 #if LDBL_MANT_DIG == 53
76 __weak_reference(ceil, ceill);
77 #endif
78