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 <sys/cdefs.h> 14 __FBSDID("$FreeBSD$"); 15 16 /* IEEE functions 17 * nextafter(x,y) 18 * return the next machine floating-point number of x in the 19 * direction toward y. 20 * Special cases: 21 */ 22 23 #include <float.h> 24 25 #include "math.h" 26 #include "math_private.h" 27 28 double nextafter(double x,double y)29 nextafter(double x, double y) 30 { 31 volatile double t; 32 int32_t hx,hy,ix,iy; 33 u_int32_t lx,ly; 34 35 EXTRACT_WORDS(hx,lx,x); 36 EXTRACT_WORDS(hy,ly,y); 37 ix = hx&0x7fffffff; /* |x| */ 38 iy = hy&0x7fffffff; /* |y| */ 39 40 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */ 41 ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */ 42 return x+y; 43 if(x==y) return y; /* x=y, return y */ 44 if((ix|lx)==0) { /* x == 0 */ 45 INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */ 46 t = x*x; 47 if(t==x) return t; else return x; /* raise underflow flag */ 48 } 49 if(hx>=0) { /* x > 0 */ 50 if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */ 51 if(lx==0) hx -= 1; 52 lx -= 1; 53 } else { /* x < y, x += ulp */ 54 lx += 1; 55 if(lx==0) hx += 1; 56 } 57 } else { /* x < 0 */ 58 if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */ 59 if(lx==0) hx -= 1; 60 lx -= 1; 61 } else { /* x > y, x += ulp */ 62 lx += 1; 63 if(lx==0) hx += 1; 64 } 65 } 66 hy = hx&0x7ff00000; 67 if(hy>=0x7ff00000) return x+x; /* overflow */ 68 if(hy<0x00100000) { /* underflow */ 69 t = x*x; 70 if(t!=x) { /* raise underflow flag */ 71 INSERT_WORDS(y,hx,lx); 72 return y; 73 } 74 } 75 INSERT_WORDS(x,hx,lx); 76 return x; 77 } 78 79 #if (LDBL_MANT_DIG == 53) 80 __weak_reference(nextafter, nexttoward); 81 __weak_reference(nextafter, nexttowardl); 82 __weak_reference(nextafter, nextafterl); 83 #endif 84