gonzui

    1: /* s_floorf.c -- float version of s_floor.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: /*
   17:  * floorf(x)
   18:  * Return x rounded toward -inf to integral value
   19:  * Method:
   20:  *      Bit twiddling.
   21:  * Exception:
   22:  *      Inexact flag raised if x not equal to floorf(x).
   23:  */
   24: 
   25: #include "math.h"
   26: #include "math_private.h"
   27: 
   28: static const float huge = 1.0e30;
   29: 
   30: float
   31: floorf(float x)
   32: {
   33:         int32_t i0,jj0;
   34:         u_int32_t i;
   35:         GET_FLOAT_WORD(i0,x);
   36:         jj0 = ((i0>>23)&0xff)-0x7f;
   37:         if(jj0<23) {
   38:             if(jj0<0) {        /* raise inexact if x != 0 */
   39:                 if(huge+x>(float)0.0) {/* return 0*sign(x) if |x|<1 */
   40:                     if(i0>=0) {i0=0;} 
   41:                     else if((i0&0x7fffffff)!=0)
   42:                         { i0=0xbf800000;}
   43:                 }
   44:             } else {
   45:                 i = (0x007fffff)>>jj0;
   46:                 if((i0&i)==0) return x; /* x is integral */
   47:                 if(huge+x>(float)0.0) {       /* raise inexact flag */
   48:                     if(i0<0) i0 += (0x00800000)>>jj0;
   49:                     i0 &= (~i);
   50:                 }
   51:             }
   52:         } else {
   53:             if(jj0==0x80) return x+x;  /* inf or NaN */
   54:             else return x;             /* x is integral */
   55:         }
   56:         SET_FLOAT_WORD(x,i0);
   57:         return x;
   58: }