gonzui

    1: /* e_hypotf.c -- float version of e_hypot.c.
    2:  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
    3:  */
    4: 
    5: /*
    6:  * ====================================================
    7:  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
    8:  *
    9:  * Developed at SunPro, a Sun Microsystems, Inc. business.
   10:  * Permission to use, copy, modify, and distribute this
   11:  * software is freely granted, provided that this notice 
   12:  * is preserved.
   13:  * ====================================================
   14:  */
   15: 
   16: #include "math.h"
   17: #include "math_private.h"
   18: 
   19: float
   20: hypotf(float x, float y)
   21: {
   22:         float a=x,b=y,t1,t2,yy1,y2,w;
   23:         int32_t j,k,ha,hb;
   24: 
   25:         GET_FLOAT_WORD(ha,x);
   26:         ha &= 0x7fffffff;
   27:         GET_FLOAT_WORD(hb,y);
   28:         hb &= 0x7fffffff;
   29:         if(hb > ha) {a=y;b=x;j=ha; ha=hb;hb=j;} else {a=x;b=y;}
   30:         SET_FLOAT_WORD(a,ha);  /* a <- |a| */
   31:         SET_FLOAT_WORD(b,hb);  /* b <- |b| */
   32:         if((ha-hb)>0xf000000) {return a+b;} /* x/y > 2**30 */
   33:         k=0;
   34:         if(ha > 0x58800000) {  /* a>2**50 */
   35:            if(ha >= 0x7f800000) {      /* Inf or NaN */
   36:                w = a+b;                        /* for sNaN */
   37:                if(ha == 0x7f800000) w = a;
   38:                if(hb == 0x7f800000) w = b;
   39:                return w;
   40:            }
   41:            /* scale a and b by 2**-60 */
   42:            ha -= 0x5d800000; hb -= 0x5d800000; k += 60;
   43:            SET_FLOAT_WORD(a,ha);
   44:            SET_FLOAT_WORD(b,hb);
   45:         }
   46:         if(hb < 0x26800000) {  /* b < 2**-50 */
   47:             if(hb <= 0x007fffff) {     /* subnormal b or 0 */      
   48:                 if(hb==0) return a;
   49:                 SET_FLOAT_WORD(t1,0x3f000000);        /* t1=2^126 */
   50:                 b *= t1;
   51:                 a *= t1;
   52:                 k -= 126;
   53:             } else {           /* scale a and b by 2^60 */
   54:                 ha += 0x5d800000;      /* a *= 2^60 */
   55:                 hb += 0x5d800000;     /* b *= 2^60 */
   56:                 k -= 60;
   57:                 SET_FLOAT_WORD(a,ha);
   58:                 SET_FLOAT_WORD(b,hb);
   59:             }
   60:         }
   61:     /* medium size a and b */
   62:         w = a-b;
   63:         if (w>b) {
   64:             SET_FLOAT_WORD(t1,ha&0xfffff000);
   65:             t2 = a-t1;
   66:             w  = sqrtf(t1*t1-(b*(-b)-t2*(a+t1)));
   67:         } else {
   68:             a  = a+a;
   69:             SET_FLOAT_WORD(yy1,hb&0xfffff000);
   70:             y2 = b - yy1;
   71:             SET_FLOAT_WORD(t1,ha+0x00800000);
   72:             t2 = a - t1;
   73:             w  = sqrtf(t1*yy1-(w*(-w)-(t1*y2+t2*b)));
   74:         }
   75:         if(k!=0) {
   76:             SET_FLOAT_WORD(t1,0x3f800000+(k<<23));
   77:             return t1*w;
   78:         } else return w;
   79: }