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
14 static 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
30 double
nextafter(double x,double y)31 nextafter(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