/*      $NetBSD: s_nexttowardf.c,v 1.5 2024/05/05 14:06:47 riastradh Exp $      */

/*
 * ====================================================
 * 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>
#if 0
__FBSDID("$FreeBSD: src/lib/msun/src/s_nexttowardf.c,v 1.3 2011/02/10 07:38:38 das Exp $");
#else
__RCSID("$NetBSD: s_nexttowardf.c,v 1.5 2024/05/05 14:06:47 riastradh Exp $");
#endif

#include <string.h>
#include <float.h>
#include <machine/ieee.h>

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

/*
 * On ports where long double is just double, reuse the ieee_double_u
 * union as if it were ieee_ext_u -- broken-down components of (long)
 * double values.
 */
#ifndef __HAVE_LONG_DOUBLE
#define ieee_ext_u      ieee_double_u
#define extu_ld         dblu_d
#define extu_ext        dblu_dbl
#define ext_sign        dbl_sign
#define ext_exp         dbl_exp
#define ext_frach       dbl_frach
#define ext_fracl       dbl_fracl
#define EXT_EXP_INFNAN  DBL_EXP_INFNAN
#define LDBL_NBIT       0
#endif

/*
 * XXX We should arrange to define LDBL_NBIT unconditionally in the
 * appropriate MD header file.
 */
#ifdef LDBL_IMPLICIT_NBIT
#define LDBL_NBIT       0
#endif

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

        GET_FLOAT_WORD(hx,x);
        ix = hx&0x7fffffff;             /* |x| */

        memset(&uy, 0, sizeof(uy));
        uy.extu_ld = y;
        uy.extu_ext.ext_frach &= ~LDBL_NBIT;

        if((ix>0x7f800000) ||
           (uy.extu_ext.ext_exp == EXT_EXP_INFNAN &&
            (uy.extu_ext.ext_frach | uy.extu_ext.ext_fracl) != 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.extu_ext.ext_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(x,hx);
                return x;
            }
        }
        SET_FLOAT_WORD(x,hx);
        return x;
}