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 /* IEEE functions
14 * nexttowardf(x,y)
15 * return the next machine floating-point number of x in the
16 * direction toward y.
17 * This is for machines which use the same binary type for double and
18 * long double.
19 * Special cases:
20 */
21
22 #include <math.h>
23 #include <float.h>
24
25 #include "math_private.h"
26
27 float
nexttowardf(float x,long double y)28 nexttowardf(float x, long double y)
29 {
30 int32_t hx,hy,ix,iy;
31 u_int32_t ly;
32
33 GET_FLOAT_WORD(hx,x);
34 EXTRACT_WORDS(hy,ly,y);
35 ix = hx&0x7fffffff; /* |x| */
36 iy = hy&0x7fffffff; /* |y| */
37
38 if((ix>0x7f800000) || /* x is nan */
39 ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */
40 return x+y;
41 if((long double) x==y) return y; /* x=y, return y */
42 if(ix==0) { /* x == 0 */
43 volatile float u;
44 SET_FLOAT_WORD(x,(u_int32_t)(hy&0x80000000)|1);/* return +-minsub*/
45 u = x;
46 u = u * u; /* raise underflow flag */
47 return x;
48 }
49 if(hx>=0) { /* x > 0 */
50 if(hy<0||(ix>>23)>(iy>>20)-0x380
51 || ((ix>>23)==(iy>>20)-0x380
52 && (ix&0x7fffff)>(((hy<<3)|(ly>>29))&0x7fffff))) /* x > y, x -= ulp */
53 hx -= 1;
54 else /* x < y, x += ulp */
55 hx += 1;
56 } else { /* x < 0 */
57 if(hy>=0||(ix>>23)>(iy>>20)-0x380
58 || ((ix>>23)==(iy>>20)-0x380
59 && (ix&0x7fffff)>(((hy<<3)|(ly>>29))&0x7fffff))) /* x < y, x -= ulp */
60 hx -= 1;
61 else /* x > y, x += ulp */
62 hx += 1;
63 }
64 hy = hx&0x7f800000;
65 if(hy>=0x7f800000) {
66 x = x+x; /* overflow */
67 return x;
68 }
69 if(hy<0x00800000) {
70 volatile float u = x*x; /* underflow */
71 if(u==x) {
72 SET_FLOAT_WORD(x,hx);
73 return x;
74 }
75 }
76 SET_FLOAT_WORD(x,hx);
77 return x;
78 }
79