contrib/openbsd_libm/src/s_nexttowardf.c

   1 /* @(#)s_nextafter.c 5.1 93/09/24 */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 /* IEEE functions
  14  *      nexttowardf(x,y)
  15  *      return the next machine floating-point number of x in the
  16  *      direction toward y.
  17  * This is for machines which use the same binary type for double and
  18  * long double.
  19  *   Special cases:
  20  */
  21
  22 #include <math.h>
  23 #include <float.h>
  24
  25 #include "math_private.h"
  26
  27 float
  28 nexttowardf(float x, long double y)
  29 {
  30         int32_t hx,hy,ix,iy;
  31         u_int32_t ly;
  32
  33         GET_FLOAT_WORD(hx,x);
  34         EXTRACT_WORDS(hy,ly,y);
  35         ix = hx&0x7fffffff;             /* |x| */
  36         iy = hy&0x7fffffff;             /* |y| */
  37
  38         if((ix>0x7f800000) ||                              /* x is nan */
  39            ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0))    /* y is nan */
  40            return x+y;
  41         if((long double) x==y) return y;        /* x=y, return y */
  42         if(ix==0) {                             /* x == 0 */
  43             volatile float u;
  44             SET_FLOAT_WORD(x,(u_int32_t)(hy&0x80000000)|1);/* return +-minsub*/
  45             u = x;
  46             u = u * u;                          /* raise underflow flag */
  47             return x;
  48         }
  49         if(hx>=0) {                             /* x > 0 */
  50             if(hy<0||(ix>>23)>(iy>>20)-0x380
  51                || ((ix>>23)==(iy>>20)-0x380
  52                    && (ix&0x7fffff)>(((hy<<3)|(ly>>29))&0x7fffff)))     /* x > y, x -= ulp */
  53                 hx -= 1;
  54             else                                /* x < y, x += ulp */
  55                 hx += 1;
  56         } else {                                /* x < 0 */
  57             if(hy>=0||(ix>>23)>(iy>>20)-0x380
  58                || ((ix>>23)==(iy>>20)-0x380
  59                    && (ix&0x7fffff)>(((hy<<3)|(ly>>29))&0x7fffff)))     /* x < y, x -= ulp */
  60                 hx -= 1;
  61             else                                /* x > y, x += ulp */
  62                 hx += 1;
  63         }
  64         hy = hx&0x7f800000;
  65         if(hy>=0x7f800000) {
  66           x = x+x;      /* overflow  */
  67           return x;
  68         }
  69         if(hy<0x00800000) {
  70             volatile float u = x*x;             /* underflow */
  71             if(u==x) {
  72                 SET_FLOAT_WORD(x,hx);
  73                 return x;
  74             }
  75         }
  76         SET_FLOAT_WORD(x,hx);
  77         return x;
  78 }