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 | |
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 | |