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 #include <LibConfig.h>
13 #include <sys/EfiCdefs.h>
14 #if defined(LIBM_SCCS) && !defined(lint)
15 __RCSID("$NetBSD: s_floor.c,v 1.11 2002/05/26 22:01:56 wiz Exp $");
16 #endif
17
18 /*
19 * floor(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 floor(x).
25 */
26
27 #include "math.h"
28 #include "math_private.h"
29
30 static const double huge = 1.0e300;
31
32 double
floor(double x)33 floor(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=i1=0;}
43 else if(((i0&0x7fffffff)|i1)!=0)
44 { i0=0xbff00000;i1=0;}
45 }
46 } else {
47 i = (0x000fffff)>>j0;
48 if(((i0&i)|i1)==0) return x; /* x is integral */
49 if(huge+x>0.0) { /* raise inexact flag */
50 if(i0<0) i0 += (0x00100000)>>j0;
51 i0 &= (~i); i1=0;
52 }
53 }
54 } else if (j0>51) {
55 if(j0==0x400) return x+x; /* inf or NaN */
56 else return x; /* x is integral */
57 } else {
58 i = ((u_int32_t)(0xffffffff))>>(j0-20);
59 if((i1&i)==0) return x; /* x is integral */
60 if(huge+x>0.0) { /* raise inexact flag */
61 if(i0<0) {
62 if(j0==20) i0+=1;
63 else {
64 j = i1+(1<<(52-j0));
65 if((int32_t)j<i1) i0 +=1 ; /* got a carry */
66 i1=j;
67 }
68 }
69 i1 &= (~i);
70 }
71 }
72 INSERT_WORDS(x,i0,i1);
73 return x;
74 }
75