1  /* s_nexttoward.c
       2   * Conversion from s_nextafter.c by Ulrich Drepper, Cygnus Support,
       3   * drepper@cygnus.com and Jakub Jelinek, jj@ultra.linux.cz.
       4   */
       5  
       6  /*
       7   * ====================================================
       8   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
       9   *
      10   * Developed at SunPro, a Sun Microsystems, Inc. business.
      11   * Permission to use, copy, modify, and distribute this
      12   * software is freely granted, provided that this notice
      13   * is preserved.
      14   * ====================================================
      15   */
      16  
      17  #if defined(LIBM_SCCS) && !defined(lint)
      18  static char rcsid[] = "$NetBSD: $";
      19  #endif
      20  
      21  /* IEEE functions
      22   *	nexttoward(x,y)
      23   *	return the next machine floating-point number of x in the
      24   *	direction toward y.
      25   *   Special cases:
      26   */
      27  
      28  #include <errno.h>
      29  #include <math.h>
      30  #include <math-barriers.h>
      31  #include <math_private.h>
      32  #include <math_ldbl_opt.h>
      33  #include <float.h>
      34  
      35  double __nexttoward(double x, long double y)
      36  {
      37  	int32_t hx,ix;
      38  	int64_t hy,iy;
      39  	uint32_t lx;
      40  	double yhi;
      41  
      42  	EXTRACT_WORDS(hx,lx,x);
      43  	yhi = ldbl_high (y);
      44  	EXTRACT_WORDS64(hy,yhi);
      45  	ix = hx&0x7fffffff;		/* |x| */
      46  	iy = hy&0x7fffffffffffffffLL;	/* |y| */
      47  
      48  	if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
      49  	   iy>0x7ff0000000000000LL)			    /* y is nan */
      50  	   return x+y;
      51  	if((long double) x==y) return y;	/* x=y, return y */
      52  	if((ix|lx)==0) {			/* x == 0 */
      53  	    double u;
      54  	    INSERT_WORDS(x,(uint32_t)((hy>>32)&0x80000000),1);/* return +-minsub */
      55  	    u = math_opt_barrier (x);
      56  	    u = u * u;
      57  	    math_force_eval (u);		/* raise underflow flag */
      58  	    return x;
      59  	}
      60  	if(hx>=0) {				/* x > 0 */
      61  	    if (x > y) {			/* x > 0 */
      62  		if(lx==0) hx -= 1;
      63  		lx -= 1;
      64  	    } else {				/* x < y, x += ulp */
      65  		lx += 1;
      66  		if(lx==0) hx += 1;
      67  	    }
      68  	} else {				/* x < 0 */
      69  	    if (x < y) {			/* x < 0 */
      70  		if(lx==0) hx -= 1;
      71  		lx -= 1;
      72  	    } else {				/* x > y, x += ulp */
      73  		lx += 1;
      74  		if(lx==0) hx += 1;
      75  	    }
      76  	}
      77  	hy = hx&0x7ff00000;
      78  	if(hy>=0x7ff00000) {
      79  	  double u = x+x;			/* overflow  */
      80  	  math_force_eval (u);
      81  	  __set_errno (ERANGE);
      82  	}
      83  	if(hy<0x00100000) {
      84  	    double u = x*x;			/* underflow */
      85  	    math_force_eval (u);		/* raise underflow flag */
      86  	    __set_errno (ERANGE);
      87  	}
      88  	INSERT_WORDS(x,hx,lx);
      89  	return x;
      90  }
      91  long_double_symbol (libm, __nexttoward, nexttoward);