1 /* @(#)s_floor.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 * floor(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 floor(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
floor(double x)30 floor(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=i1=0;}
40 else if(((i0&0x7fffffff)|i1)!=0)
41 { i0=0xbff00000;i1=0;}
42 }
43 } else {
44 i = (0x000fffff)>>jj0;
45 if(((i0&i)|i1)==0) return x; /* x is integral */
46 if(huge+x>0.0) { /* raise inexact flag */
47 if(i0<0) i0 += (0x00100000)>>jj0;
48 i0 &= (~i); i1=0;
49 }
50 }
51 } else if (jj0>51) {
52 if(jj0==0x400) return x+x; /* inf or NaN */
53 else return x; /* x is integral */
54 } else {
55 i = ((u_int32_t)(0xffffffff))>>(jj0-20);
56 if((i1&i)==0) return x; /* x is integral */
57 if(huge+x>0.0) { /* raise inexact flag */
58 if(i0<0) {
59 if(jj0==20) i0+=1;
60 else {
61 j = i1+(1<<(52-jj0));
62 if(j<i1) i0 +=1 ; /* got a carry */
63 i1=j;
64 }
65 }
66 i1 &= (~i);
67 }
68 }
69 INSERT_WORDS(x,i0,i1);
70 return x;
71 }
72 DEF_STD(floor);
73 LDBL_MAYBE_CLONE(floor);
74