1/* s_nexttoward.c
2 * Conversion from s_nextafter.c by Ulrich Drepper, Cygnus Support,
3 * drepper@cygnus.com and Jakub Jelinek, jj@ultra.linux.cz.
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)
18static 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 <math_ldbl_opt.h>
33#include <float.h>
34
35double __nexttoward(double x, long double y)
36{
37 int32_t hx,ix;
38 int64_t hy,iy;
39 uint32_t lx;
40 double yhi;
41
42 EXTRACT_WORDS(hx,lx,x);
43 yhi = ldbl_high (y);
44 EXTRACT_WORDS64(hy,yhi);
45 ix = hx&0x7fffffff; /* |x| */
46 iy = hy&0x7fffffffffffffffLL; /* |y| */
47
48 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
49 iy>0x7ff0000000000000LL) /* y is nan */
50 return x+y;
51 if((long double) x==y) return y; /* x=y, return y */
52 if((ix|lx)==0) { /* x == 0 */
53 double u;
54 INSERT_WORDS(x,(uint32_t)((hy>>32)&0x80000000),1);/* return +-minsub */
55 u = math_opt_barrier (x);
56 u = u * u;
57 math_force_eval (u); /* raise underflow flag */
58 return x;
59 }
60 if(hx>=0) { /* x > 0 */
61 if (x > y) { /* x > 0 */
62 if(lx==0) hx -= 1;
63 lx -= 1;
64 } else { /* x < y, x += ulp */
65 lx += 1;
66 if(lx==0) hx += 1;
67 }
68 } else { /* x < 0 */
69 if (x < y) { /* x < 0 */
70 if(lx==0) hx -= 1;
71 lx -= 1;
72 } else { /* x > y, x += ulp */
73 lx += 1;
74 if(lx==0) hx += 1;
75 }
76 }
77 hy = hx&0x7ff00000;
78 if(hy>=0x7ff00000) {
79 double u = x+x; /* overflow */
80 math_force_eval (u);
81 __set_errno (ERANGE);
82 }
83 if(hy<0x00100000) {
84 double u = x*x; /* underflow */
85 math_force_eval (u); /* raise underflow flag */
86 __set_errno (ERANGE);
87 }
88 INSERT_WORDS(x,hx,lx);
89 return x;
90}
91long_double_symbol (libm, __nexttoward, nexttoward);
92

source code of glibc/sysdeps/ieee754/ldbl-128ibm/s_nexttoward.c