/* @(#)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.
 * ====================================================
 */

/* IEEE functions
 *      nexttoward(x,y)
 *      return the next machine floating-point number of x in the
 *      direction toward y.
 *   Special cases:
 */

#include <math.h>
#include <float.h>

#include "math_private.h"

double
nexttoward(double x, long double y)
{
        int32_t hx,ix,iy;
        u_int32_t lx,hy,ly,esy;

        EXTRACT_WORDS(hx,lx,x);
        GET_LDOUBLE_WORDS(esy,hy,ly,y);
        ix = hx&0x7fffffff;             /* |x| */
        iy = esy&0x7fff;                /* |y| */

        if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
           ((iy>=0x7fff)&&(hy|ly)!=0))          /* y is nan */
           return x+y;
        if((long double) x==y) return y;        /* x=y, return y */
        if((ix|lx)==0) {                        /* x == 0 */
            volatile double u;
            INSERT_WORDS(x,(esy&0x8000)<<16,1); /* return +-minsub */
            u = x;
            u = u * u;                          /* raise underflow flag */
            return x;
        }
        if(hx>=0) {                             /* x > 0 */
            if (esy>=0x8000||((ix>>20)&0x7ff)>iy-0x3c00
                || (((ix>>20)&0x7ff)==iy-0x3c00
                    && (((hx<<11)|(lx>>21))>(hy&0x7fffffff)
                        || (((hx<<11)|(lx>>21))==(hy&0x7fffffff)
                            && (lx<<11)>ly)))) {        /* x > y, x -= ulp */
                if(lx==0) hx -= 1;
                lx -= 1;
            } else {                            /* x < y, x += ulp */
                lx += 1;
                if(lx==0) hx += 1;
            }
        } else {                                /* x < 0 */
            if (esy<0x8000||((ix>>20)&0x7ff)>iy-0x3c00
                || (((ix>>20)&0x7ff)==iy-0x3c00
                    && (((hx<<11)|(lx>>21))>(hy&0x7fffffff)
                        || (((hx<<11)|(lx>>21))==(hy&0x7fffffff)
                            && (lx<<11)>ly))))  {/* x < y, x -= ulp */
                if(lx==0) hx -= 1;
                lx -= 1;
            } else {                            /* x > y, x += ulp */
                lx += 1;
                if(lx==0) hx += 1;
            }
        }
        hy = hx&0x7ff00000;
        if(hy>=0x7ff00000) {
          x = x+x;      /* overflow  */
          return x;
        }
        if(hy<0x00100000) {
            volatile double u = x*x;            /* underflow */
            if(u==x) {
                INSERT_WORDS(x,hx,lx);
                return x;
            }
        }
        INSERT_WORDS(x,hx,lx);
        return x;
}