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/* @(#)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;
}
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