1 /* @(#)s_nextafter.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  * Copyright (c) 2002, 2003 David Schultz <das@FreeBSD.ORG>
12  */
13 
14 /* IEEE functions
15  *	nextafterl(x,y)
16  *	return the next machine floating-point number of x in the
17  *	direction toward y.
18  *   Special cases:
19  */
20 
21 #include <math.h>
22 #include <sys/cdefs.h>
23 
24 #include "math_private.h"
25 
26 union IEEEl2bits {
27 	long double	e;
28 	struct {
29 		unsigned int	manl	:32;
30 		unsigned int	manh	:32;
31 		unsigned int	exp	:15;
32 		unsigned int	sign	:1;
33 		unsigned int	junkl	:16;
34 		unsigned int	junkh	:32;
35 	} bits;
36 	struct {
37 		unsigned long	man	:64;
38 		unsigned int	expsign	:16;
39 		unsigned long	junk	:48;
40 	} xbits;
41 };
42 
43 #define	LDBL_NBIT	0x80000000
44 #define	mask_nbit_l(u)	((u).bits.manh &= ~LDBL_NBIT)
45 
46 long double
47 nextafterl(long double x, long double y)
48 {
49 	volatile long double t;
50 	union IEEEl2bits ux, uy;
51 
52 	ux.e = x;
53 	uy.e = y;
54 
55 	if ((ux.bits.exp == 0x7fff &&
56 	     ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl) != 0) ||
57 	    (uy.bits.exp == 0x7fff &&
58 	     ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0))
59 	   return x+y;	/* x or y is nan */
60 	if(x==y) return y;		/* x=y, return y */
61 	if(x==0.0) {
62 	    ux.bits.manh = 0;			/* return +-minsubnormal */
63 	    ux.bits.manl = 1;
64 	    ux.bits.sign = uy.bits.sign;
65 	    t = ux.e*ux.e;
66 	    if(t==ux.e) return t; else return ux.e; /* raise underflow flag */
67 	}
68 	if((x>0.0) ^ (x<y)) {			/* x -= ulp */
69 	    if(ux.bits.manl==0) {
70 		if ((ux.bits.manh&~LDBL_NBIT)==0)
71 		    ux.bits.exp -= 1;
72 		ux.bits.manh = (ux.bits.manh - 1) | (ux.bits.manh & LDBL_NBIT);
73 	    }
74 	    ux.bits.manl -= 1;
75 	} else {				/* x += ulp */
76 	    ux.bits.manl += 1;
77 	    if(ux.bits.manl==0) {
78 		ux.bits.manh = (ux.bits.manh + 1) | (ux.bits.manh & LDBL_NBIT);
79 		if ((ux.bits.manh&~LDBL_NBIT)==0)
80 		    ux.bits.exp += 1;
81 	    }
82 	}
83 	if(ux.bits.exp==0x7fff) return x+x;	/* overflow  */
84 	if(ux.bits.exp==0) {			/* underflow */
85 	    mask_nbit_l(ux);
86 	    t = ux.e * ux.e;
87 	    if(t!=ux.e)			/* raise underflow flag */
88 		return ux.e;
89 	}
90 	return ux.e;
91 }
92 
93 __strong_reference(nextafterl, nexttowardl);
94