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