gonzui

    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:         }
   72:         SET_FLOAT_WORD(x,hx);
   73:         return x;
   74: }