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  */
12 
13 #include <sys/cdefs.h>
14 __FBSDID("$FreeBSD$");
15 
16 /* IEEE functions
17  *	nextafter(x,y)
18  *	return the next machine floating-point number of x in the
19  *	direction toward y.
20  *   Special cases:
21  */
22 
23 #include <float.h>
24 
25 #include "fpmath.h"
26 #include "math.h"
27 #include "math_private.h"
28 
29 #if LDBL_MAX_EXP != 0x4000
30 #error "Unsupported long double format"
31 #endif
32 
33 long double
nextafterl(long double x,long double y)34 nextafterl(long double x, long double y)
35 {
36 	volatile long double t;
37 	union IEEEl2bits ux, uy;
38 
39 	ux.e = x;
40 	uy.e = y;
41 
42 	if ((ux.bits.exp == 0x7fff &&
43 	     ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl) != 0) ||
44 	    (uy.bits.exp == 0x7fff &&
45 	     ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0))
46 	   return x+y;	/* x or y is nan */
47 	if(x==y) return y;		/* x=y, return y */
48 	if(x==0.0) {
49 	    ux.bits.manh = 0;			/* return +-minsubnormal */
50 	    ux.bits.manl = 1;
51 	    ux.bits.sign = uy.bits.sign;
52 	    t = ux.e*ux.e;
53 	    if(t==ux.e) return t; else return ux.e; /* raise underflow flag */
54 	}
55 	if(x>0.0 ^ x<y) {			/* x -= ulp */
56 	    if(ux.bits.manl==0) {
57 		if ((ux.bits.manh&~LDBL_NBIT)==0)
58 		    ux.bits.exp -= 1;
59 		ux.bits.manh = (ux.bits.manh - 1) | (ux.bits.manh & LDBL_NBIT);
60 	    }
61 	    ux.bits.manl -= 1;
62 	} else {				/* x += ulp */
63 	    ux.bits.manl += 1;
64 	    if(ux.bits.manl==0) {
65 		ux.bits.manh = (ux.bits.manh + 1) | (ux.bits.manh & LDBL_NBIT);
66 		if ((ux.bits.manh&~LDBL_NBIT)==0)
67 		    ux.bits.exp += 1;
68 	    }
69 	}
70 	if(ux.bits.exp==0x7fff) return x+x;	/* overflow  */
71 	if(ux.bits.exp==0) {			/* underflow */
72 	    mask_nbit_l(ux);
73 	    t = ux.e * ux.e;
74 	    if(t!=ux.e)			/* raise underflow flag */
75 		return ux.e;
76 	}
77 	return ux.e;
78 }
79 
80 __strong_reference(nextafterl, nexttowardl);
81