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 * floor(x)
14 * Return x rounded toward -inf to integral value
15 * Method:
16 * Bit twiddling.
17 * Exception:
18 * Inexact flag raised if x not equal to floor(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
floor(double x)29 floor(double x)
30 {
31 int32_t i0,i1,j0;
32 u_int32_t i,j;
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) {/* return 0*sign(x) if |x|<1 */
38 if(i0>=0) {i0=i1=0;}
39 else if(((i0&0x7fffffff)|i1)!=0)
40 { i0=0xbff00000;i1=0;}
41 }
42 } else {
43 i = (0x000fffff)>>j0;
44 if(((i0&i)|i1)==0) return x; /* x is integral */
45 if(huge+x>0.0) { /* raise inexact flag */
46 if(i0<0) i0 += (0x00100000)>>j0;
47 i0 &= (~i); i1=0;
48 }
49 }
50 } else if (j0>51) {
51 if(j0==0x400) return x+x; /* inf or NaN */
52 else return x; /* x is integral */
53 } else {
54 i = ((u_int32_t)(0xffffffff))>>(j0-20);
55 if((i1&i)==0) return x; /* x is integral */
56 if(huge+x>0.0) { /* raise inexact flag */
57 if(i0<0) {
58 if(j0==20) i0+=1;
59 else {
60 j = i1+(1<<(52-j0));
61 if(j<i1) i0 +=1 ; /* got a carry */
62 i1=j;
63 }
64 }
65 i1 &= (~i);
66 }
67 }
68 INSERT_WORDS(x,i0,i1);
69 return x;
70 }
71
72 #if LDBL_MANT_DIG == 53
73 __weak_reference(floor, floorl);
74 #endif
75