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-barriers.h>
  31 #include <math_private.h>
  32 #include <float.h>
  33
  34 double __nexttoward(double x, long double y)
  35 {
  36         int32_t hx,ix,iy;
  37         uint32_t lx,hy,ly,esy;
  38
  39         EXTRACT_WORDS(hx,lx,x);
  40         GET_LDOUBLE_WORDS(esy,hy,ly,y);
  41         ix = hx&0x7fffffff;             /* |x| */
  42         iy = esy&0x7fff;                /* |y| */
  43
  44         if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
  45            ((iy>=0x7fff)&&(hy|ly)!=0))        /* y is nan */
  46            return x+y;
  47         if((long double) x==y) return y;        /* x=y, return y */
  48         if((ix|lx)==0) {                        /* x == 0 */
  49             double u;
  50             INSERT_WORDS(x,(esy&0x8000)<<16,1); /* return +-minsub */
  51             u = math_opt_barrier (x);
  52             u = u * u;
  53             math_force_eval (u);                /* raise underflow flag */
  54             return x;
  55         }
  56         if(hx>=0) {                             /* x > 0 */
  57             if (x > y) {                        /* x -= ulp */
  58                 if(lx==0) hx -= 1;
  59                 lx -= 1;
  60             } else {                            /* x < y, x += ulp */
  61                 lx += 1;
  62                 if(lx==0) hx += 1;
  63             }
  64         } else {                                /* x < 0 */
  65             if (x < y) {                        /* x -= ulp */
  66                 if(lx==0) hx -= 1;
  67                 lx -= 1;
  68             } else {                            /* x > y, x += ulp */
  69                 lx += 1;
  70                 if(lx==0) hx += 1;
  71             }
  72         }
  73         hy = hx&0x7ff00000;
  74         if(hy>=0x7ff00000) {
  75           double u = x+x;                       /* overflow  */
  76           math_force_eval (u);
  77           __set_errno (ERANGE);
  78         }
  79         if(hy<0x00100000) {
  80             double u = x*x;                     /* underflow */
  81             math_force_eval (u);                /* raise underflow flag */
  82             __set_errno (ERANGE);
  83         }
  84         INSERT_WORDS(x,hx,lx);
  85         return x;
  86 }
  87 weak_alias (__nexttoward, nexttoward)