1 
2 /* @(#)s_floor.c 5.1 93/09/24 */
3 /*
4  * ====================================================
5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6  *
7  * Developed at SunPro, a Sun Microsystems, Inc. business.
8  * Permission to use, copy, modify, and distribute this
9  * software is freely granted, provided that this notice
10  * is preserved.
11  * ====================================================
12  */
13 
14 /*
15 FUNCTION
16 <<floor>>, <<floorf>>, <<ceil>>, <<ceilf>>---floor and ceiling
17 INDEX
18 	floor
19 INDEX
20 	floorf
21 INDEX
22 	ceil
23 INDEX
24 	ceilf
25 
26 ANSI_SYNOPSIS
27 	#include <math.h>
28 	double floor(double <[x]>);
29         float floorf(float <[x]>);
30         double ceil(double <[x]>);
31         float ceilf(float <[x]>);
32 
33 TRAD_SYNOPSIS
34 	#include <math.h>
35         double floor(<[x]>)
36 	double <[x]>;
37         float floorf(<[x]>)
38 	float <[x]>;
39         double ceil(<[x]>)
40 	double <[x]>;
41         float ceilf(<[x]>)
42 	float <[x]>;
43 
44 DESCRIPTION
45 <<floor>> and <<floorf>> find
46 @tex
47 $\lfloor x \rfloor$,
48 @end tex
49 the nearest integer less than or equal to <[x]>.
50 <<ceil>> and <<ceilf>> find
51 @tex
52 $\lceil x\rceil$,
53 @end tex
54 the nearest integer greater than or equal to <[x]>.
55 
56 RETURNS
57 <<floor>> and <<ceil>> return the integer result as a double.
58 <<floorf>> and <<ceilf>> return the integer result as a float.
59 
60 PORTABILITY
61 <<floor>> and <<ceil>> are ANSI.
62 <<floorf>> and <<ceilf>> are extensions.
63 
64 
65 */
66 
67 /*
68  * floor(x)
69  * Return x rounded toward -inf to integral value
70  * Method:
71  *	Bit twiddling.
72  * Exception:
73  *	Inexact flag raised if x not equal to floor(x).
74  */
75 
76 #include "fdlibm.h"
77 
78 #ifndef _DOUBLE_IS_32BITS
79 
80 #ifdef __STDC__
81 static const double huge = 1.0e300;
82 #else
83 static double huge = 1.0e300;
84 #endif
85 
86 #ifdef __STDC__
floor(double x)87 	double floor(double x)
88 #else
89 	double floor(x)
90 	double x;
91 #endif
92 {
93 	__int32_t i0,i1,j0;
94 	__uint32_t i,j;
95 	EXTRACT_WORDS(i0,i1,x);
96 	j0 = ((i0>>20)&0x7ff)-0x3ff;
97 	if(j0<20) {
98 	    if(j0<0) { 	/* raise inexact if x != 0 */
99 		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
100 		    if(i0>=0) {i0=i1=0;}
101 		    else if(((i0&0x7fffffff)|i1)!=0)
102 			{ i0=0xbff00000;i1=0;}
103 		}
104 	    } else {
105 		i = (0x000fffff)>>j0;
106 		if(((i0&i)|i1)==0) return x; /* x is integral */
107 		if(huge+x>0.0) {	/* raise inexact flag */
108 		    if(i0<0) i0 += (0x00100000)>>j0;
109 		    i0 &= (~i); i1=0;
110 		}
111 	    }
112 	} else if (j0>51) {
113 	    if(j0==0x400) return x+x;	/* inf or NaN */
114 	    else return x;		/* x is integral */
115 	} else {
116 	    i = ((__uint32_t)(0xffffffff))>>(j0-20);
117 	    if((i1&i)==0) return x;	/* x is integral */
118 	    if(huge+x>0.0) { 		/* raise inexact flag */
119 		if(i0<0) {
120 		    if(j0==20) i0+=1;
121 		    else {
122 			j = i1+(1<<(52-j0));
123 			if(j<i1) i0 +=1 ; 	/* got a carry */
124 			i1=j;
125 		    }
126 		}
127 		i1 &= (~i);
128 	    }
129 	}
130 	INSERT_WORDS(x,i0,i1);
131 	return x;
132 }
133 
134 #endif /* _DOUBLE_IS_32BITS */
135