nsz Git - musl/blob - src/math/s_nextafter.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  *      nextafter(x,y)
  15  *      return the next machine floating-point number of x in the
  16  *      direction toward y.
  17  *   Special cases:
  18  */
  19
  20 #include <math.h>
  21 #include "math_private.h"
  22
  23 double
  24 nextafter(double x, double y)
  25 {
  26         volatile double t;
  27         int32_t hx,hy,ix,iy;
  28         uint32_t lx,ly;
  29
  30         EXTRACT_WORDS(hx,lx,x);
  31         EXTRACT_WORDS(hy,ly,y);
  32         ix = hx&0x7fffffff;             /* |x| */
  33         iy = hy&0x7fffffff;             /* |y| */
  34
  35         if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
  36            ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0))     /* y is nan */
  37            return x+y;
  38         if(x==y) return y;              /* x=y, return y */
  39         if((ix|lx)==0) {                        /* x == 0 */
  40             INSERT_WORDS(x,hy&0x80000000,1);    /* return +-minsubnormal */
  41             t = x*x;
  42             if(t==x) return t; else return x;   /* raise underflow flag */
  43         }
  44         if(hx>=0) {                             /* x > 0 */
  45             if(hx>hy||((hx==hy)&&(lx>ly))) {    /* x > y, x -= ulp */
  46                 if(lx==0) hx -= 1;
  47                 lx -= 1;
  48             } else {                            /* x < y, x += ulp */
  49                 lx += 1;
  50                 if(lx==0) hx += 1;
  51             }
  52         } else {                                /* x < 0 */
  53             if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
  54                 if(lx==0) hx -= 1;
  55                 lx -= 1;
  56             } else {                            /* x > y, x += ulp */
  57                 lx += 1;
  58                 if(lx==0) hx += 1;
  59             }
  60         }
  61         hy = hx&0x7ff00000;
  62         if(hy>=0x7ff00000) return x+x;  /* overflow  */
  63         if(hy<0x00100000) {             /* underflow */
  64             t = x*x;
  65             if(t!=x) {          /* raise underflow flag */
  66                 INSERT_WORDS(y,hx,lx);
  67                 return y;
  68             }
  69         }
  70         INSERT_WORDS(x,hx,lx);
  71         return x;
  72 }