source: vendor/FreeBSD-msun/current/src/s_nexttowardf.c

/*
 * ====================================================
 * 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.
 * ====================================================
 */

#ifndef lint
static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_nexttowardf.c,v 1.1 2005/03/07 04:57:38 das Exp $";
#endif

#include <float.h>

#include "fpmath.h"
#include "math.h"
#include "math_private.h"

#define LDBL_INFNAN_EXP (LDBL_MAX_EXP * 2 - 1)

float
nexttowardf(float x, long double y)
{
        union IEEEl2bits uy;
        volatile float t;
        int32_t hx,ix;

        GET_FLOAT_WORD(hx,x);
        ix = hx&0x7fffffff;             /* |x| */
        uy.e = y;

        if((ix>0x7f800000) ||
           (uy.bits.exp == LDBL_INFNAN_EXP &&
            ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0))
           return x+y;  /* x or y is nan */
        if(x==y) return (float)y;               /* x=y, return y */
        if(ix==0) {                             /* x == 0 */
            SET_FLOAT_WORD(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 ^ x < y)                       /* x -= ulp */
            hx -= 1;
        else                                    /* x += ulp */
            hx += 1;
        ix = hx&0x7f800000;
        if(ix>=0x7f800000) return x+x;  /* overflow  */
        if(ix<0x00800000) {             /* underflow */
            t = x*x;
            if(t!=x) {          /* raise underflow flag */
                SET_FLOAT_WORD(y,hx);
                return y;
            }
        }
        SET_FLOAT_WORD(x,hx);
        return x;
}