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 #if 0
15 __FBSDID("$FreeBSD: src/lib/msun/src/s_trunc.c,v 1.1 2004/06/20 09:25:43 das Exp $");
16 #endif
17 #if defined(LIBM_SCCS) && !defined(lint)
18 __RCSID("$NetBSD: s_trunc.c,v 1.4 2013/11/13 12:58:11 joerg Exp $");
19 #endif
20
21 /*
22 * trunc(x)
23 * Return x rounded toward 0 to integral value
24 * Method:
25 * Bit twiddling.
26 * Exception:
27 * Inexact flag raised if x not equal to trunc(x).
28 */
29
30 #include "math.h"
31 #include "math_private.h"
32
33 #ifndef __HAVE_LONG_DOUBLE
34 __strong_alias(_truncl, trunc)
35 __weak_alias(truncl, trunc)
36 #endif
37
38 static const double huge = 1.0e300;
39
40 double
trunc(double x)41 trunc(double x)
42 {
43 int32_t i0,i1,jj0;
44 uint32_t i;
45 EXTRACT_WORDS(i0,i1,x);
46 jj0 = ((i0>>20)&0x7ff)-0x3ff;
47 if(jj0<20) {
48 if(jj0<0) { /* raise inexact if x != 0 */
49 if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */
50 i0 &= 0x80000000U;
51 i1 = 0;
52 }
53 } else {
54 i = (0x000fffff)>>jj0;
55 if(((i0&i)|i1)==0) return x; /* x is integral */
56 if(huge+x>0.0) { /* raise inexact flag */
57 i0 &= (~i); i1=0;
58 }
59 }
60 } else if (jj0>51) {
61 if(jj0==0x400) return x+x; /* inf or NaN */
62 else return x; /* x is integral */
63 } else {
64 i = ((u_int32_t)(0xffffffff))>>(jj0-20);
65 if((i1&i)==0) return x; /* x is integral */
66 if(huge+x>0.0) /* raise inexact flag */
67 i1 &= (~i);
68 }
69 INSERT_WORDS(x,i0,i1);
70 return x;
71 }
72