lib/libm/src/s_floorf.c

   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 }