modules/fdlibm/src/s_floorf.cpp

   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 //#include <sys/cdefs.h>
  17 //__FBSDID("$FreeBSD$");
  18
  19 /*
  20  * floorf(x)
  21  * Return x rounded toward -inf to integral value
  22  * Method:
  23  *      Bit twiddling.
  24  * Exception:
  25  *      Inexact flag raised if x not equal to floorf(x).
  26  */
  27
  28 #include "math_private.h"
  29
  30 static const float huge = 1.0e30;
  31
  32 float
  33 floorf(float x)
  34 {
  35         int32_t i0,j0;
  36         u_int32_t i;
  37         GET_FLOAT_WORD(i0,x);
  38         j0 = ((i0>>23)&0xff)-0x7f;
  39         if(j0<23) {
  40             if(j0<0) {  /* raise inexact if x != 0 */
  41                 if(huge+x>(float)0.0) {/* return 0*sign(x) if |x|<1 */
  42                     if(i0>=0) {i0=0;}
  43                     else if((i0&0x7fffffff)!=0)
  44                         { i0=0xbf800000;}
  45                 }
  46             } else {
  47                 i = (0x007fffff)>>j0;
  48                 if((i0&i)==0) return x; /* x is integral */
  49                 if(huge+x>(float)0.0) { /* raise inexact flag */
  50                     if(i0<0) i0 += (0x00800000)>>j0;
  51                     i0 &= (~i);
  52                 }
  53             }
  54         } else {
  55             if(j0==0x80) return x+x;    /* inf or NaN */
  56             else return x;              /* x is integral */
  57         }
  58         SET_FLOAT_WORD(x,i0);
  59         return x;
  60 }