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_nextafter.c,v 1.11 2005/03/07 21:27:37 das Exp $";
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 "math.h"
28#include "math_private.h"
29
30double
31nextafter(double x, double y)
32{
33	volatile double t;
34	int32_t hx,hy,ix,iy;
35	u_int32_t lx,ly;
36
37	EXTRACT_WORDS(hx,lx,x);
38	EXTRACT_WORDS(hy,ly,y);
39	ix = hx&0x7fffffff;		/* |x| */
40	iy = hy&0x7fffffff;		/* |y| */
41
42	if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
43	   ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0))     /* y is nan */
44	   return x+y;
45	if(x==y) return y;		/* x=y, return y */
46	if((ix|lx)==0) {			/* x == 0 */
47	    INSERT_WORDS(x,hy&0x80000000,1);	/* return +-minsubnormal */
48	    t = x*x;
49	    if(t==x) return t; else return x;	/* raise underflow flag */
50	}
51	if(hx>=0) {				/* x > 0 */
52	    if(hx>hy||((hx==hy)&&(lx>ly))) {	/* x > y, x -= ulp */
53		if(lx==0) hx -= 1;
54		lx -= 1;
55	    } else {				/* x < y, x += ulp */
56		lx += 1;
57		if(lx==0) hx += 1;
58	    }
59	} else {				/* x < 0 */
60	    if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
61		if(lx==0) hx -= 1;
62		lx -= 1;
63	    } else {				/* x > y, x += ulp */
64		lx += 1;
65		if(lx==0) hx += 1;
66	    }
67	}
68	hy = hx&0x7ff00000;
69	if(hy>=0x7ff00000) return x+x;	/* overflow  */
70	if(hy<0x00100000) {		/* underflow */
71	    t = x*x;
72	    if(t!=x) {		/* raise underflow flag */
73	        INSERT_WORDS(y,hx,lx);
74		return y;
75	    }
76	}
77	INSERT_WORDS(x,hx,lx);
78	return x;
79}
80
81#if (LDBL_MANT_DIG == 53)
82__weak_reference(nextafter, nexttoward);
83__weak_reference(nextafter, nexttowardl);
84__weak_reference(nextafter, nextafterl);
85#endif
86