1143217Sdas/* @(#)s_nextafter.c 5.1 93/09/24 */
2143217Sdas/*
3143217Sdas * ====================================================
4143217Sdas * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5143217Sdas *
6143217Sdas * Developed at SunPro, a Sun Microsystems, Inc. business.
7143217Sdas * Permission to use, copy, modify, and distribute this
8143217Sdas * software is freely granted, provided that this notice
9143217Sdas * is preserved.
10143217Sdas * ====================================================
11143217Sdas */
12143217Sdas
13176451Sdas#include <sys/cdefs.h>
14176451Sdas__FBSDID("$FreeBSD$");
15143217Sdas
16143217Sdas/*
17143217Sdas * We assume that a long double has a 15-bit exponent.  On systems
18143217Sdas * where long double is the same as double, nexttoward() is an alias
19143217Sdas * for nextafter(), so we don't use this routine.
20143217Sdas */
21143217Sdas
22143217Sdas#include <float.h>
23143217Sdas
24143217Sdas#include "fpmath.h"
25143217Sdas#include "math.h"
26143217Sdas#include "math_private.h"
27143217Sdas
28143217Sdas#if LDBL_MAX_EXP != 0x4000
29143217Sdas#error "Unsupported long double format"
30143217Sdas#endif
31143217Sdas
32143217Sdasdouble
33143217Sdasnexttoward(double x, long double y)
34143217Sdas{
35143217Sdas	union IEEEl2bits uy;
36143217Sdas	volatile double t;
37143217Sdas	int32_t hx,ix;
38143217Sdas	u_int32_t lx;
39143217Sdas
40143217Sdas	EXTRACT_WORDS(hx,lx,x);
41143217Sdas	ix = hx&0x7fffffff;		/* |x| */
42143217Sdas	uy.e = y;
43143217Sdas
44143217Sdas	if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||
45143217Sdas	    (uy.bits.exp == 0x7fff &&
46143217Sdas	     ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0))
47143217Sdas	   return x+y;	/* x or y is nan */
48143217Sdas	if(x==y) return (double)y;		/* x=y, return y */
49143217Sdas	if(x==0.0) {
50143217Sdas	    INSERT_WORDS(x,uy.bits.sign<<31,1);	/* return +-minsubnormal */
51143217Sdas	    t = x*x;
52143217Sdas	    if(t==x) return t; else return x;	/* raise underflow flag */
53143217Sdas	}
54143217Sdas	if(hx>0.0 ^ x < y) {			/* x -= ulp */
55143217Sdas	    if(lx==0) hx -= 1;
56143217Sdas	    lx -= 1;
57143217Sdas	} else {				/* x += ulp */
58143217Sdas	    lx += 1;
59143217Sdas	    if(lx==0) hx += 1;
60143217Sdas	}
61143217Sdas	ix = hx&0x7ff00000;
62143217Sdas	if(ix>=0x7ff00000) return x+x;	/* overflow  */
63143217Sdas	if(ix<0x00100000) {		/* underflow */
64143217Sdas	    t = x*x;
65143217Sdas	    if(t!=x) {		/* raise underflow flag */
66218510Sdas	        INSERT_WORDS(x,hx,lx);
67218510Sdas		return x;
68143217Sdas	    }
69143217Sdas	}
70143217Sdas	INSERT_WORDS(x,hx,lx);
71143217Sdas	return x;
72143217Sdas}
73