sysdeps/ieee754/ldbl-96/s_nexttoward.c

   1 /* s_nexttoward.c
   2  * Conversion from s_nextafter.c by Ulrich Drepper, Cygnus Support,
   3  * drepper@cygnus.com.
   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_private.h>
  31 #include <float.h>
  32
  33 double __nexttoward(double x, long double y)
  34 {
  35         int32_t hx,ix,iy;
  36         u_int32_t lx,hy,ly,esy;
  37
  38         EXTRACT_WORDS(hx,lx,x);
  39         GET_LDOUBLE_WORDS(esy,hy,ly,y);
  40         ix = hx&0x7fffffff;             /* |x| */
  41         iy = esy&0x7fff;                /* |y| */
  42
  43         if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
  44            ((iy>=0x7fff)&&(hy|ly)!=0))        /* y is nan */
  45            return x+y;
  46         if((long double) x==y) return y;        /* x=y, return y */
  47         if((ix|lx)==0) {                        /* x == 0 */
  48             double u;
  49             INSERT_WORDS(x,(esy&0x8000)<<16,1); /* return +-minsub */
  50             u = math_opt_barrier (x);
  51             u = u * u;
  52             math_force_eval (u);                /* raise underflow flag */
  53             return x;
  54         }
  55         if(hx>=0) {                             /* x > 0 */
  56             if (x > y) {                        /* x -= ulp */
  57                 if(lx==0) hx -= 1;
  58                 lx -= 1;
  59             } else {                            /* x < y, x += ulp */
  60                 lx += 1;
  61                 if(lx==0) hx += 1;
  62             }
  63         } else {                                /* x < 0 */
  64             if (x < y) {                        /* x -= ulp */
  65                 if(lx==0) hx -= 1;
  66                 lx -= 1;
  67             } else {                            /* x > y, x += ulp */
  68                 lx += 1;
  69                 if(lx==0) hx += 1;
  70             }
  71         }
  72         hy = hx&0x7ff00000;
  73         if(hy>=0x7ff00000) {
  74           double u = x+x;                       /* overflow  */
  75           math_force_eval (u);
  76           __set_errno (ERANGE);
  77         }
  78         if(hy<0x00100000) {
  79             double u = x*x;                     /* underflow */
  80             math_force_eval (u);                /* raise underflow flag */
  81             __set_errno (ERANGE);
  82         }
  83         INSERT_WORDS(x,hx,lx);
  84         return x;
  85 }
  86 weak_alias (__nexttoward, nexttoward)