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 /*
14 * ceil(x)
15 * Return x rounded toward -inf to integral value
16 * Method:
17 * Bit twiddling.
18 * Exception:
19 * Inexact flag raised if x not equal to ceil(x).
20 */
21
22 #include <float.h>
23 #include <math.h>
24
25 #include "math_private.h"
26
27 static const double huge = 1.0e300;
28
29 double
ceil(double x)30 ceil(double x)
31 {
32 int32_t i0,i1,jj0;
33 u_int32_t i,j;
34 EXTRACT_WORDS(i0,i1,x);
35 jj0 = ((i0>>20)&0x7ff)-0x3ff;
36 if(jj0<20) {
37 if(jj0<0) { /* raise inexact if x != 0 */
38 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
39 if(i0<0) {i0=0x80000000;i1=0;}
40 else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;}
41 }
42 } else {
43 i = (0x000fffff)>>jj0;
44 if(((i0&i)|i1)==0) return x; /* x is integral */
45 if(huge+x>0.0) { /* raise inexact flag */
46 if(i0>0) i0 += (0x00100000)>>jj0;
47 i0 &= (~i); i1=0;
48 }
49 }
50 } else if (jj0>51) {
51 if(jj0==0x400) return x+x; /* inf or NaN */
52 else return x; /* x is integral */
53 } else {
54 i = ((u_int32_t)(0xffffffff))>>(jj0-20);
55 if((i1&i)==0) return x; /* x is integral */
56 if(huge+x>0.0) { /* raise inexact flag */
57 if(i0>0) {
58 if(jj0==20) i0+=1;
59 else {
60 j = i1 + (1<<(52-jj0));
61 if(j<i1) i0+=1; /* got a carry */
62 i1 = j;
63 }
64 }
65 i1 &= (~i);
66 }
67 }
68 INSERT_WORDS(x,i0,i1);
69 return x;
70 }
71
72 #if LDBL_MANT_DIG == DBL_MANT_DIG
73 __strong_alias(ceill, ceil);
74 #endif /* LDBL_MANT_DIG == DBL_MANT_DIG */
75