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 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