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 #include <math.h>
14 #include <float.h>
15
16 #include "math_private.h"
17
18 float
nexttowardf(float x,long double y)19 nexttowardf(float x, long double y)
20 {
21 int32_t hx,ix,iy;
22 u_int32_t hy,ly,esy;
23
24 GET_FLOAT_WORD(hx,x);
25 GET_LDOUBLE_WORDS(esy,hy,ly,y);
26 ix = hx&0x7fffffff; /* |x| */
27 iy = esy&0x7fff; /* |y| */
28
29 if((ix>0x7f800000) || /* x is nan */
30 (iy>=0x7fff&&((hy|ly)!=0))) /* y is nan */
31 return x+y;
32 if((long double) x==y) return y; /* x=y, return y */
33 if(ix==0) { /* x == 0 */
34 volatile float u;
35 SET_FLOAT_WORD(x,((esy&0x8000)<<16)|1);/* return +-minsub*/
36 u = x;
37 u = u * u; /* raise underflow flag */
38 return x;
39 }
40 if(hx>=0) { /* x > 0 */
41 if(esy>=0x8000||((ix>>23)&0xff)>iy-0x3f80
42 || (((ix>>23)&0xff)==iy-0x3f80
43 && ((ix&0x7fffff)<<8)>(hy&0x7fffffff))) {/* x > y, x -= ulp */
44 hx -= 1;
45 } else { /* x < y, x += ulp */
46 hx += 1;
47 }
48 } else { /* x < 0 */
49 if(esy<0x8000||((ix>>23)&0xff)>iy-0x3f80
50 || (((ix>>23)&0xff)==iy-0x3f80
51 && ((ix&0x7fffff)<<8)>(hy&0x7fffffff))) {/* x < y, x -= ulp */
52 hx -= 1;
53 } else { /* x > y, x += ulp */
54 hx += 1;
55 }
56 }
57 hy = hx&0x7f800000;
58 if(hy>=0x7f800000) {
59 x = x+x; /* overflow */
60 return x;
61 }
62 if(hy<0x00800000) {
63 volatile float u = x*x; /* underflow */
64 }
65 SET_FLOAT_WORD(x,hx);
66 return x;
67 }
68