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: src/lib/msun/src/s_nexttoward.c,v 1.1 2005/03/07 04:56:46 das Exp $";
15#endif
16
17/*
18 * We assume that a long double has a 15-bit exponent.  On systems
19 * where long double is the same as double, nexttoward() is an alias
20 * for nextafter(), so we don't use this routine.
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
33double
34nexttoward(double x, long double y)
35{
36	union IEEEl2bits uy;
37	volatile double t;
38	int32_t hx,ix;
39	u_int32_t lx;
40
41	EXTRACT_WORDS(hx,lx,x);
42	ix = hx&0x7fffffff;		/* |x| */
43	uy.e = y;
44
45	if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=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 (double)y;		/* x=y, return y */
50	if(x==0.0) {
51	    INSERT_WORDS(x,uy.bits.sign<<31,1);	/* return +-minsubnormal */
52	    t = x*x;
53	    if(t==x) return t; else return x;	/* raise underflow flag */
54	}
55	if(hx>0.0 ^ x < y) {			/* x -= ulp */
56	    if(lx==0) hx -= 1;
57	    lx -= 1;
58	} else {				/* x += ulp */
59	    lx += 1;
60	    if(lx==0) hx += 1;
61	}
62	ix = hx&0x7ff00000;
63	if(ix>=0x7ff00000) return x+x;	/* overflow  */
64	if(ix<0x00100000) {		/* underflow */
65	    t = x*x;
66	    if(t!=x) {		/* raise underflow flag */
67	        INSERT_WORDS(y,hx,lx);
68		return y;
69	    }
70	}
71	INSERT_WORDS(x,hx,lx);
72	return x;
73}
74