1 /* s_nexttoward.c
2 * Conversion from s_nextafter.c by Ulrich Drepper, Cygnus Support,
3 * drepper@cygnus.com.
4 */
5
6 /*
7 * ====================================================
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 *
10 * Developed at SunPro, a Sun Microsystems, Inc. business.
11 * Permission to use, copy, modify, and distribute this
12 * software is freely granted, provided that this notice
13 * is preserved.
14 * ====================================================
15 */
16
17 #if defined(LIBM_SCCS) && !defined(lint)
18 static char rcsid[] = "$NetBSD: $";
19 #endif
20
21 /* IEEE functions
22 * nexttoward(x,y)
23 * return the next machine floating-point number of x in the
24 * direction toward y.
25 * Special cases:
26 */
27
28 #include <errno.h>
29 #include <math.h>
30 #include <math-barriers.h>
31 #include <math_private.h>
32 #include <float.h>
33
__nexttoward(double x,long double y)34 double __nexttoward(double x, long double y)
35 {
36 int32_t hx,ix,iy;
37 uint32_t lx,hy,ly,esy;
38
39 EXTRACT_WORDS(hx,lx,x);
40 GET_LDOUBLE_WORDS(esy,hy,ly,y);
41 ix = hx&0x7fffffff; /* |x| */
42 iy = esy&0x7fff; /* |y| */
43
44 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
45 ((iy>=0x7fff)&&(hy|ly)!=0)) /* y is nan */
46 return x+y;
47 if((long double) x==y) return y; /* x=y, return y */
48 if((ix|lx)==0) { /* x == 0 */
49 double u;
50 INSERT_WORDS(x,(esy&0x8000)<<16,1); /* return +-minsub */
51 u = math_opt_barrier (x);
52 u = u * u;
53 math_force_eval (u); /* raise underflow flag */
54 return x;
55 }
56 if(hx>=0) { /* x > 0 */
57 if (x > y) { /* x -= ulp */
58 if(lx==0) hx -= 1;
59 lx -= 1;
60 } else { /* x < y, x += ulp */
61 lx += 1;
62 if(lx==0) hx += 1;
63 }
64 } else { /* x < 0 */
65 if (x < y) { /* x -= ulp */
66 if(lx==0) hx -= 1;
67 lx -= 1;
68 } else { /* x > y, x += ulp */
69 lx += 1;
70 if(lx==0) hx += 1;
71 }
72 }
73 hy = hx&0x7ff00000;
74 if(hy>=0x7ff00000) {
75 double u = x+x; /* overflow */
76 math_force_eval (u);
77 __set_errno (ERANGE);
78 }
79 if(hy<0x00100000) {
80 double u = x*x; /* underflow */
81 math_force_eval (u); /* raise underflow flag */
82 __set_errno (ERANGE);
83 }
84 INSERT_WORDS(x,hx,lx);
85 return x;
86 }
87 weak_alias (__nexttoward, nexttoward)
88