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  * $NetBSD: s_floorf.c,v 1.7 2002/05/26 22:01:56 wiz Exp $
  16  * $DragonFly: src/lib/libm/src/s_floorf.c,v 1.1 2005/07/26 21:15:20 joerg Exp $
  17  */
  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.h>
  29 #include "math_private.h"
  30
  31 static const float huge = 1.0e30;
  32
  33 float
  34 floorf(float x)
  35 {
  36         int32_t i0,j0;
  37         u_int32_t i;
  38         GET_FLOAT_WORD(i0,x);
  39         j0 = ((i0>>23)&0xff)-0x7f;
  40         if(j0<23) {
  41             if(j0<0) {  /* raise inexact if x != 0 */
  42                 if(huge+x>(float)0.0) {/* return 0*sign(x) if |x|<1 */
  43                     if(i0>=0) {i0=0;}
  44                     else if((i0&0x7fffffff)!=0)
  45                         { i0=0xbf800000;}
  46                 }
  47             } else {
  48                 i = (0x007fffff)>>j0;
  49                 if((i0&i)==0) return x; /* x is integral */
  50                 if(huge+x>(float)0.0) { /* raise inexact flag */
  51                     if(i0<0) i0 += (0x00800000)>>j0;
  52                     i0 &= (~i);
  53                 }
  54             }
  55         } else {
  56             if(j0==0x80) return x+x;    /* inf or NaN */
  57             else return x;              /* x is integral */
  58         }
  59         SET_FLOAT_WORD(x,i0);
  60         return x;
  61 }