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 #ifndef lint
14 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_floor.c,v 1.9 2003/07/23 04:53:46 peter Exp $";
15 #endif
16
17 /*
18 * floor(x)
19 * Return x rounded toward -inf to integral value
20 * Method:
21 * Bit twiddling.
22 * Exception:
23 * Inexact flag raised if x not equal to floor(x).
24 */
25
26 #include "math.h"
27 #include "math_private.h"
28
29 static const double huge = 1.0e300;
30
31 double
floor(double x)32 floor(double x)
33 {
34 int32_t i0,i1,j0;
35 u_int32_t i,j;
36 EXTRACT_WORDS(i0,i1,x);
37 j0 = ((i0>>20)&0x7ff)-0x3ff;
38 if(j0<20) {
39 if(j0<0) { /* raise inexact if x != 0 */
40 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
41 if(i0>=0) {i0=i1=0;}
42 else if(((i0&0x7fffffff)|i1)!=0)
43 { i0=0xbff00000;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