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 <features.h>*/
22 /* Prevent math.h from defining a colliding inline */
23 #undef __USE_EXTERN_INLINES
24 #include "math_libm.h"
25 #include "math_private.h"
26
27 #ifdef __WATCOMC__ /* Watcom defines huge=__huge */
28 #undef huge
29 #endif
30
31 static const double huge = 1.0e300;
32
floor(double x)33 double 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); i1=0;
52 }
53 }
54 } else if (j0>51) {
55 if(j0==0x400) return x+x; /* inf or NaN */
56 else return x; /* x is integral */
57 } else {
58 i = ((u_int32_t)(0xffffffff))>>(j0-20);
59 if((i1&i)==0) return x; /* x is integral */
60 if(huge+x>0.0) { /* raise inexact flag */
61 if(i0<0) {
62 if(j0==20) i0+=1;
63 else {
64 j = i1+(1<<(52-j0));
65 if(j<(u_int32_t)i1) i0 +=1 ; /* got a carry */
66 i1=j;
67 }
68 }
69 i1 &= (~i);
70 }
71 }
72 INSERT_WORDS(x,i0,i1);
73 return x;
74 }
75 libm_hidden_def(floor)
76