| /* @(#)s_nextafter.c 5.1 93/09/24 */ |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| #include <sys/cdefs.h> |
| __FBSDID("$FreeBSD$"); |
| |
| /* |
| * We assume that a long double has a 15-bit exponent. On systems |
| * where long double is the same as double, nexttoward() is an alias |
| * for nextafter(), so we don't use this routine. |
| */ |
| |
| #include <float.h> |
| |
| #include "fpmath.h" |
| #include "math.h" |
| #include "math_private.h" |
| |
| #if LDBL_MAX_EXP != 0x4000 |
| #error "Unsupported long double format" |
| #endif |
| |
| double |
| nexttoward(double x, long double y) |
| { |
| union IEEEl2bits uy; |
| volatile double t; |
| int32_t hx,ix; |
| u_int32_t lx; |
| |
| EXTRACT_WORDS(hx,lx,x); |
| ix = hx&0x7fffffff; /* |x| */ |
| uy.e = y; |
| |
| if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || |
| (uy.bits.exp == 0x7fff && |
| ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0)) |
| return x+y; /* x or y is nan */ |
| if(x==y) return (double)y; /* x=y, return y */ |
| if(x==0.0) { |
| INSERT_WORDS(x,uy.bits.sign<<31,1); /* return +-minsubnormal */ |
| t = x*x; |
| if(t==x) return t; else return x; /* raise underflow flag */ |
| } |
| if(hx>0.0 ^ x < y) { /* x -= ulp */ |
| if(lx==0) hx -= 1; |
| lx -= 1; |
| } else { /* x += ulp */ |
| lx += 1; |
| if(lx==0) hx += 1; |
| } |
| ix = hx&0x7ff00000; |
| if(ix>=0x7ff00000) return x+x; /* overflow */ |
| if(ix<0x00100000) { /* underflow */ |
| t = x*x; |
| if(t!=x) { /* raise underflow flag */ |
| INSERT_WORDS(x,hx,lx); |
| return x; |
| } |
| } |
| INSERT_WORDS(x,hx,lx); |
| return x; |
| } |