1 /*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 */
11
12 /*
13 * trunc(x)
14 * Return x rounded toward 0 to integral value
15 * Method:
16 * Bit twiddling.
17 * Exception:
18 * Inexact flag raised if x not equal to trunc(x).
19 */
20
21 #include <float.h>
22
23 #include "math.h"
24 #include "math_private.h"
25
26 static const double huge = 1.0e300;
27
28 double
trunc(double x)29 trunc(double x)
30 {
31 int32_t i0,i1,j0;
32 u_int32_t i;
33 EXTRACT_WORDS(i0,i1,x);
34 j0 = ((i0>>20)&0x7ff)-0x3ff;
35 if(j0<20) {
36 if(j0<0) { /* raise inexact if x != 0 */
37 if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */
38 i0 &= 0x80000000U;
39 i1 = 0;
40 }
41 } else {
42 i = (0x000fffff)>>j0;
43 if(((i0&i)|i1)==0) return x; /* x is integral */
44 if(huge+x>0.0) { /* raise inexact flag */
45 i0 &= (~i); i1=0;
46 }
47 }
48 } else if (j0>51) {
49 if(j0==0x400) return x+x; /* inf or NaN */
50 else return x; /* x is integral */
51 } else {
52 i = ((u_int32_t)(0xffffffff))>>(j0-20);
53 if((i1&i)==0) return x; /* x is integral */
54 if(huge+x>0.0) /* raise inexact flag */
55 i1 &= (~i);
56 }
57 INSERT_WORDS(x,i0,i1);
58 return x;
59 }
60
61 #if LDBL_MANT_DIG == 53
62 __weak_reference(trunc, truncl);
63 #endif
64