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 /* 17 * We assume that a long double has a 15-bit exponent. On systems 18 * where long double is the same as double, nexttoward() is an alias 19 * for nextafter(), so we don't use this routine. 20 */ 21 22 #include <float.h> 23 24 #include "fpmath.h" 25 #include "math.h" 26 #include "math_private.h" 27 28 #if LDBL_MAX_EXP != 0x4000 29 #error "Unsupported long double format" 30 #endif 31 32 double 33 nexttoward(double x, long double y) 34 { 35 union IEEEl2bits uy; 36 volatile double t; 37 int32_t hx,ix; 38 u_int32_t lx; 39 40 EXTRACT_WORDS(hx,lx,x); 41 ix = hx&0x7fffffff; /* |x| */ 42 uy.e = y; 43 44 if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || 45 (uy.bits.exp == 0x7fff && 46 ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0)) 47 return x+y; /* x or y is nan */ 48 if(x==y) return (double)y; /* x=y, return y */ 49 if(x==0.0) { 50 INSERT_WORDS(x,uy.bits.sign<<31,1); /* return +-minsubnormal */ 51 t = x*x; 52 if(t==x) return t; else return x; /* raise underflow flag */ 53 } 54 if(hx>0.0 ^ x < y) { /* x -= ulp */ 55 if(lx==0) hx -= 1; 56 lx -= 1; 57 } else { /* x += ulp */ 58 lx += 1; 59 if(lx==0) hx += 1; 60 } 61 ix = hx&0x7ff00000; 62 if(ix>=0x7ff00000) return x+x; /* overflow */ 63 if(ix<0x00100000) { /* underflow */ 64 t = x*x; 65 if(t!=x) { /* raise underflow flag */ 66 INSERT_WORDS(x,hx,lx); 67 return x; 68 } 69 } 70 INSERT_WORDS(x,hx,lx); 71 return x; 72 } 73