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/*
17 * We assume that a long double has a 15-bit exponent.  On systems
18 * where long double is the same as double, nexttoward() is an alias
19 * for nextafter(), so we don't use this routine.
20 */
21
22#include <float.h>
23
24#include "fpmath.h"
25#include "math.h"
26#include "math_private.h"
27
28#if LDBL_MAX_EXP != 0x4000
29#error "Unsupported long double format"
30#endif
31
32double
33nexttoward(double x, long double y)
34{
35	union IEEEl2bits uy;
36	volatile double t;
37	int32_t hx,ix;
38	u_int32_t lx;
39
40	EXTRACT_WORDS(hx,lx,x);
41	ix = hx&0x7fffffff;		/* |x| */
42	uy.e = y;
43
44	if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||
45	    (uy.bits.exp == 0x7fff &&
46	     ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0))
47	   return x+y;	/* x or y is nan */
48	if(x==y) return (double)y;		/* x=y, return y */
49	if(x==0.0) {
50	    INSERT_WORDS(x,uy.bits.sign<<31,1);	/* return +-minsubnormal */
51	    t = x*x;
52	    if(t==x) return t; else return x;	/* raise underflow flag */
53	}
54	if(hx>0.0 ^ x < y) {			/* x -= ulp */
55	    if(lx==0) hx -= 1;
56	    lx -= 1;
57	} else {				/* x += ulp */
58	    lx += 1;
59	    if(lx==0) hx += 1;
60	}
61	ix = hx&0x7ff00000;
62	if(ix>=0x7ff00000) return x+x;	/* overflow  */
63	if(ix<0x00100000) {		/* underflow */
64	    t = x*x;
65	    if(t!=x) {		/* raise underflow flag */
66	        INSERT_WORDS(x,hx,lx);
67		return x;
68	    }
69	}
70	INSERT_WORDS(x,hx,lx);
71	return x;
72}
73