s_nextafterl.c revision 143217 
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#ifndef lint
14static char rcsid[] = "$FreeBSD: head/lib/msun/src/s_nextafterl.c 143217 2005-03-07 04:56:46Z das $";
15#endif
16
17/* IEEE functions
18 *	nextafter(x,y)
19 *	return the next machine floating-point number of x in the
20 *	direction toward y.
21 *   Special cases:
22 */
23
24#include <sys/cdefs.h>
25#include <float.h>
26
27#include "fpmath.h"
28#include "math.h"
29#include "math_private.h"
30
31#if LDBL_MAX_EXP != 0x4000
32#error "Unsupported long double format"
33#endif
34
35long double
36nextafterl(long double x, long double y)
37{
38	volatile long double t;
39	union IEEEl2bits ux, uy;
40
41	ux.e = x;
42	uy.e = y;
43
44	if ((ux.bits.exp == 0x7fff &&
45	     ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl) != 0) ||
46	    (uy.bits.exp == 0x7fff &&
47	     ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0))
48	   return x+y;	/* x or y is nan */
49	if(x==y) return y;		/* x=y, return y */
50	if(x==0.0) {
51	    ux.bits.manh = 0;			/* return +-minsubnormal */
52	    ux.bits.manl = 1;
53	    ux.bits.sign = uy.bits.sign;
54	    t = ux.e*ux.e;
55	    if(t==ux.e) return t; else return ux.e; /* raise underflow flag */
56	}
57	if(x>0.0 ^ x<y) {			/* x -= ulp */
58	    if(ux.bits.manl==0) {
59		if ((ux.bits.manh&~LDBL_NBIT)==0)
60		    ux.bits.exp -= 1;
61		ux.bits.manh = (ux.bits.manh - 1) | (ux.bits.manh & LDBL_NBIT);
62	    }
63	    ux.bits.manl -= 1;
64	} else {				/* x += ulp */
65	    ux.bits.manl += 1;
66	    if(ux.bits.manl==0) {
67		ux.bits.manh = (ux.bits.manh + 1) | (ux.bits.manh & LDBL_NBIT);
68		if ((ux.bits.manh&~LDBL_NBIT)==0)
69		    ux.bits.exp += 1;
70	    }
71	}
72	if(ux.bits.exp==0x7fff) return x+x;	/* overflow  */
73	if(ux.bits.exp==0) {			/* underflow */
74	    mask_nbit_l(ux);
75	    t = ux.e * ux.e;
76	    if(t!=ux.e)			/* raise underflow flag */
77		return ux.e;
78	}
79	return ux.e;
80}
81
82__strong_reference(nextafterl, nexttowardl);
83