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 #include <sys/cdefs.h>
14 __FBSDID("$FreeBSD$");
15
16 /*
17 * floor(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 floor(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
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);
52 i1=0;
53 }
54 }
55 } else if (j0>51) {
56 if (j0==0x400) return x+x; /* inf or NaN */
57 else return x; /* x is integral */
58 } else {
59 i = ((u_int32_t)(0xffffffff))>>(j0-20);
60 if ((i1&i)==0) return x; /* x is integral */
61 if (huge+x>0.0) { /* raise inexact flag */
62 if (i0<0) {
63 if (j0==20) i0+=1;
64 else {
65 j = i1+(1<<(52-j0));
66 if (j<(u_int32_t)i1) i0 +=1 ; /* got a carry */
67 i1=j;
68 }
69 }
70 i1 &= (~i);
71 }
72 }
73 INSERT_WORDS(x,i0,i1);
74 return x;
75 }
76
77 #if SUPPORT_LONG_DOUBLE
78
79 #if LDBL_MANT_DIG == 53
80 __weak_reference(floor, floorl);
81 #endif
82
83 #endif
84