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 * trunc(x)
15 * Return x rounded toward 0 to integral value
16 * Method:
17 * Bit twiddling.
18 * Exception:
19 * Inexact flag raised if x not equal to trunc(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
trunc(double x)30 trunc(double x)
31 {
32 int32_t i0,i1,jj0;
33 u_int32_t i;
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) {/* |x|<1, so return 0*sign(x) */
39 i0 &= 0x80000000U;
40 i1 = 0;
41 }
42 } else {
43 i = (0x000fffff)>>jj0;
44 if(((i0&i)|i1)==0) return x; /* x is integral */
45 if(huge+x>0.0) { /* raise inexact flag */
46 i0 &= (~i); i1=0;
47 }
48 }
49 } else if (jj0>51) {
50 if(jj0==0x400) return x+x; /* inf or NaN */
51 else return x; /* x is integral */
52 } else {
53 i = ((u_int32_t)(0xffffffff))>>(jj0-20);
54 if((i1&i)==0) return x; /* x is integral */
55 if(huge+x>0.0) /* raise inexact flag */
56 i1 &= (~i);
57 }
58 INSERT_WORDS(x,i0,i1);
59 return x;
60 }
61
62 #if LDBL_MANT_DIG == DBL_MANT_DIG
63 __strong_alias(truncl, trunc);
64 #endif /* LDBL_MANT_DIG == DBL_MANT_DIG */
65